Porsche Engineering Services, Inc. ULSAB Program Phase 2. Final Report. Ultra Light Steel Auto Body. Consortium

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2 Porsche Engineering Services, Inc. ULSAB Program Phase 2 Final Report to the Ultra Light Steel Auto Body Consortium

3 Ultra Light Steel Auto Body Member Companies Aceralia AK Steel Bethlehem BHP Steel British Steel Cockerill Sambre CSN Dofasco Hoogovens Inland Kawasaki Steel Kobe Krakatau Krupp Hoesch LTV Steel National Steel Nippon Steel NKK POSCO Preussag Rouge Steel SIDERAR SIDMAR SOLLAC SSAB Stelco Sumitomo Tata Thyssen US Steel Group USIMINAS VSZ VOEST-ALPINE WCI Weirton

4 ULSAB Final Report Table of Contents Preface 1. Executive Summary 2. Phase 2 Introduction 2.1. Phase 2 Program Goal 2.2. Phase 2 Design and Analysis 2.3. Demonstration Hardware (DH) 2.4. Scope of Work 2.5. Materials 2.6. Testing of Test Unit 2.7. Phase 2 Program Timing 3. ULSAB Phase 2 Package 3.1. General Approach 3.2. Package Definition Vehicle Concept Type Exterior Dimensions Interior Dimensions Main Component Definition Underfloor Clearance Seating Position Visibility Study Horizontal and Vertical Obstruction A-Pillar Obstruction Gear Shift Lever Position Pedal Position Bumper Height Definition 3.3. Package Drawings Table of Contents - Page 1

5 4. Styling 4.1. Approach D Styling Phase Sketching Clinic Electronic Paint Styling Theme Selection D Styling Model Surface Release 4.4. Rendering 5. Design and Engineering 5.1. Phase 2 Design and Engineering Approach 5.2. Design and Engineering Process 5.3. ULSAB Phase 2 Design Description Parts List Demonstration Hardware ULSAB Structure Mass ULSAB Demonstration Hardware Mass Mass of Brackets and Reinforcements Phase ULSAB Structure Mass Comparison Phase 1 Phase DH Part Manufacturing Processes Material Grades Material Thickness 5.4. Detail Design Weld Flange Standards Weld Flanges for Spot or Laser Welding Scalloped Spot Weld Flanges Locator, Tooling and Electrophoresis Holes Design Refinement Table of Contents - Page 2

6 6. CAE Analysis Results 6.1. Selected Tests for CAE 6.2. Static and Dynamic Stiffness Torsional Stiffness Bending Stiffness Normal Modes 6.3. Crash Analysis AMS Offset Crash NCAP 100% Frontal Crash Rear Crash Side Impact Analysis Roof Crush (FMVSS 216) 6.4. CAE Analysis Summary 7. Materials and Processes 7.1. Material Selection Material Selection Process Definition of Strength Levels Supplier Selection 7.2. Material Specifications General Specifications Material Classes Mild Steel Definition High Strength Steel Definition Ultra High Strength Steel Definition Sandwich Material Definition Material Documentation 7.3. Tailor Welded Blanks Selection of Welding Process Weld Line Layout Production Blank Layout Table of Contents - Page 3

7 7.4. Hydroforming General Process Description Benefit for the Project Forming Simulation (Review) Tube Manufacturing Process Steps for Rail Side Roof Results 7.5. Hydromechanical Sheet Forming General Process Description Benefit for the Project Process Limitations Results 8. Parts Manufacturing 8.1. Supplier Selection 8.2. Simultaneous Engineering 8.3. Part Manufacturing Feasibility 8.4. Quality Criteria 9. DH Build 9.1. Introduction 9.2. Joining Technologies Laser Welding Spot Welding Active Gas Metal Arc Welding (MAG) Adhesive Bonding 9.3. Flexible Modular Assembly Fixture System 9.4. Design of Assembly Fixtures 9.5. DH Build Assembly Team Build of the Test Unit Build of DH #2 to DH #13 Table of Contents - Page 4

8 9.6. Quality Body Quality Control Team Quality Control Measurements of DHs 9.7. Conclusion 10. Testing and Results Scope of Work Targets Static Rigidity Test Setup General Static Torsion Static Bending Results Static Torsion Static Bending Modal Analysis Test Setup Results Masses in Test Configuration Summary 11. Economic Analysis Introduction The Process of Cost Estimation Overview Cost Model Algorithm Development General Inputs Fabrication Input Assembly Input Cost Model Description Table of Contents - Page 5

9 11.4. ULSAB Cost Results Overall Cost Results Cost Breakdown for Fabrication Cost Breakdown for Assembly Cost Analysis for New Technologies and Materials Sensitivity Analysis Body Structure Comparative Study Overview Assumptions Overall Results Conclusion NOTE: The cost models may be found on the Porsche ULSAB Phase 2 CD ROM Version Summary of Phase 2 Results ULSAB Final Report Appendix Table of Contents NOTE: The following information is located on the Porsche ULSAB Phase 2 CD ROM Version Parts Book 1.1. Exploded View 1.2. Index Parts Book Sheets 1.3. Parts Book Sheets 1.4. Index Parts book, Brackets & Reinforcements 1.5. Parts Book Sheets Brackets & Reinforcements Table of Contents - Page 6

10 2. Part Drawings 2.1. Exploded View 2.2. Parts List Sorted by Part Number 2.3. Parts List Sorted by Material Grade 2.4. Part Drawings 3. Typical Sections 3.1. Overview Illustration 3.2. Index Typical Sections 3.3. Typical Section Sheets 4. Assembly 4.1. Assembly Tree 4.2. Index Weld Assemblies 4.3. Weld Assembly Drawings 4.4. Assembly Sequence Illustrations 4.5. Index Bolted and / or Bonded Assemblies 4.6. Assembly Drawings, Bolted and / or Bonded Parts 4.7. Assembly Illustrations Bolted and / or Bonded Parts 5. Package Drawings 5.1. Side View 5.2. Plan View 5.3. Front & Rear View 6. Economic Analysis 6.1. Assembly System Data 6.2. Stamping Process Sheets Table of Contents - Page 7

11 Preface In 1994, the steel industry, through the Ultra Light Steel Auto Body Consortium (ULSAB), commissioned Porsche Engineering Services, Inc. (PES) to conduct a concept phase (Phase 1) of the ULSAB project to determine if a substantially lighter steel body structure could be designed. In September 1995, worldwide auto industry attention was focused on the study when the results of Phase 1 were announced. The results also affected the growth of the ULSAB Consortium to 35 member steel companies, representing 18 nations worldwide. Encouraged by the results of Phase 1, the ULSAB Consortium once again commissioned PES to continue with Phase 2, the validation of the Phase 1 concepts, culminating in the build of the demonstration hardware. Phase 2 proved that the weight reduction, predicted in Phase 1, could be achieved. The use of high strength steels, tailor welded blanks, hydroforming and laser welding in assembly were particular challenges to overcome in Phase 2. ULSAB Consortium members committed themselves to supplying all steel materials, as well as the tailor welded blanks and raw materials for hydroforming, for all parts to be manufactured. The focus of Phase 2 was the same as in Phase 1, i.e., weight reduction without compromising safety or structural performance. Without altering the aggressive targets for mass and structural performance, the safety requirements were increased in Phase 2 in response to growing industry and government concern for increased auto safety. It was imperative to keep up with safety requirement changes that occurred during the course of the program, which ran from spring 1994 to spring As a result, it was necessary to analyze the ULSAB structure for offset crash behavior. With this new challenge, and valuable input gathered in discussions with OEMs during the presentation of Phase 1 findings, PES and the ULSAB Consortium commenced Phase 2. Preface - Page 1

12 Phase 2 ended in Spring 1998 with the debut of the ULSAB demonstration hardware and will prove the Phase 1 concept to be not only feasible, but that performance targets will be exceeded by 60% for torsional rigidity, 48% for bending rigidity and 50% for the normal mode frequency. Relative to the benchmark average, mass reduction remained at 25%, while crash analysis showed excellent results for the selected crash analysis events, including the offset crash. As a result of Phase 2, the use of high strength steels in the ULSAB demonstration hardware structure has now increased to 90% relative to its mass. The trend toward using high strength steel and new technologies to reduce body structure mass while improving safety, can be seen already in recently launched cars. The new Porsche Boxster, for example, uses 30% high strength steel, as well as tailored blanking, hydroforming and laser welding in assembly. Cost analysis in Phase 1 was conducted by IBIS Associates under contract to the ULSAB Consortium. In Phase 2, a more detailed cost analysis study was conducted, under the supervision of PES with the support of ULSAB consortium member companies. With the detailed information provided with the concept validation in Phase 2, a new cost model was created and the cost to produce the ULSAB structure was analyzed. The results show that it is possible to reduce the mass of body structures without cost penalty. Preface - Page 2

13 1. Executive Summary Engineering Services, Inc.

14 1. Executive Summary Ultra Light Steel Auto Body (ULSAB) Phase 2 Introduction On behalf of an international Consortium of 35 of the world s leading sheet-steel producers from 18 countries, Porsche Engineering Services, Inc. (PES) in Troy, Michigan, was responsible for the program management, design, engineering, and the building of the demonstration hardware (DH). In addition, PES conducted the economic analysis study for the Ultra Light Steel Auto Body (ULSAB) program. Program Goal The goal of the ULSAB program was to develop a light-weight body structure design that is predominantly steel. This goal included: Providing a significant mass reduction based on a future reference vehicle Meeting functional and structural performance targets Providing concepts that will be applicable for future car programs Program Structure In order to achieve the above-mentioned goals the program was structured in three phases: Phase 1 Concept Development (paper study) Phase 2 Concept Validation (build of demonstration hardware) Phase 3 Vehicle Feasibility (total vehicle prototype assembly and evaluation) Chapter 1 - Page 1

15 Phase 1 Concept In September 1995, the results of Phase 1 were published. In this phase, the ULSAB program concentrated on developing design concepts for light-weight body structures and validating crashworthiness. Based on benchmarking data, the performance of a future reference vehicle was predicted and the structural performance targets for the ULSAB structure, excluding doors, rear deck lid, hood and front fenders were established. Because the ULSAB program focuses on mass reduction, a much more aggressive target was set for mass than for the other structural performance targets. These targets were: ULSAB Future Reference Performance Targets* Vehicle Prediction Mass [ 200 kg 250 kg Static torsional rigidity m Nm/deg Nm/deg Static bending rigidity m N/mm N/mm First body structure mode m 40 Hz 40 Hz * All targets were set for body structure with glass, except the target for mass For the concept validation, the following crash analysis was performed in Phase 1: NCAP, 100% frontal crash at 35 mph Rear moving barrier crash at 35 mph (FMVSS 301) EEVC, side impact crash at 50 km/h (with rigid barrier) Roof crush (FMVSS 216) The analytical results of Phase 1 were: Performance Phase 1 Results* Mass 205 kg Static torsional rigidity Nm/deg Static bending rigidity N/mm First body structure mode 51 Hz *Structural performance results were calculated with glass; the mass excludes glass Chapter 1 - Page 2

16 With the exception of mass, the results exceeded the targets. Mass was calculated at 205 kg and slightly above the aggressive target of 200 kg. An independent cost study indicated that, based on a North American manufacturing scenerio, the Phase 1 concept could cost less to produce than comparable current vehicle structures. This result, based on the relatively low level of detail of the ULSAB Phase 1 concept, indicated that a light weight structure could make substantial use of high strength steel, tailor welded blanks, laser welding in assembly, and hydroforming, and end up in the cost range of structures of similar size using a more conventional approach at a higher mass. Phase 2 - Validation The Phase 1 design concept and its structural and crash performance results having had a relatively low mass, provided an excellent foundation for Phase 2 of the ULSAB program. Based on the success of this Phase 1 paper study, and the positive recognition by OEMs around the world, the ULSAB Consortium commissioned PES to undertake Phase 2 starting in November The overall goal of Phase 2 was the validation of Phase 1 results, culminating in the build of the ULSAB demonstration hardware structure. The tasks and responsibilities of Phase 2 for PES, besides the program management, were to manage the necessary detail design, engineering, crash analysis, material selection, design optimization for manufacturing, supplier selection for parts and to assemble, test and deliver the demonstration hardware to the ULSAB Consortium. In addition, PES was responsible for a detailed cost analysis based on the Phase 2 detailed design. Chapter 1 - Page 3

17 Crash Analysis During the course of the ULSAB program after the start in Spring 1994, the public demanded increased vehicle safety, and governments reacted with new requirements for crashworthiness. Therefore, the decision was made prior to the beginning of Phase 2, to analyze and to design the ULSAB structure for offset crash. This would enhance the credibility of the results. The AMS (Auto Motor Sport) 50% offset frontal crash at 55 km/h was considered the most severe test at that time and would represent the structural requirements an offset crash demands. This test was then added to the Phase 1 previously selected crash analysis events. For side impact crash analysis, a deformable barrier was used instead of the rigid barrier as used in Phase 1. The following crash analysis was performed in Phase 2: AMS, 50% frontal offset crash at 55 km/h NCAP, 100% frontal crash at 35 mph (FMVSS 208) Side impact crash at 50 km/h (96/27 EG, with deformable barrier) Rear moving barrier crash at 35 mph (FMVSS 301) Roof crush (FMVSS 216) All crash calculations indicate excellent crash behavior of the ULSAB structure, even at speeds that exceed federal requirements. The front and rear impacts were run at 5 mph above the required limit, meaning 36% more energy had to be absorbed in the frontal impact. The offset crash also confirmed the overall integrity of the structure. The roof crush analysis validated that the federal standard requirement was met, partialy due to the hydroformed side roof rail concept design. Package At the start of Phase 2, as a result of various discussions with OEMs during the presentation of Phase 1 results, the ULSAB package was re-examined. In order to make the results of Phase 2 more credible, the decision was made not to consider secondary mass savings. This resulted in significant changes in several areas of the body structure. Chapter 1 - Page 4

18 The relatively small engine specified in Phase 1 was replaced by an average size 3-liter V6, necessitating a complete redesign of the front-end structure, including a revised front suspension layout and subframe design. The rear suspension also was revised and the rear rails redesigned accordingly. Essentially, the whole structure was redesigned, from front to rear bumper, but it still maintained the structure features as developed in Phase I, such as the side roof rail and the smooth load flow concept of front and rear rails into the rocker. Styling Using the revised package and the adjusted body structure design, styling the ULSAB was the next challenge. Styling became necessary to create the surfaces for the body side outer panel with its integrated exposed rear quarter panel, the windshield, the backlight and the roof panel. The styling concept for the greenhouse had to consider, in order to integrate, the side roof rail, as well as the overlapping upper door frame concept. This door concept was chosen mainly for cosmetic reasons; to cover the visible weld seams, in the upper door opening area of the body side outer panel which were caused by the tailor welded blank design of the body side outer panel. For the overall styling approach, the decision was made to create a neutral, not too futuristic or radical, more conservative styling. Styling was the first major milestone in Phase 2 and was performed entirely by computer-aided styling (CAS). Design and Engineering After the exterior styling was created, the package was then optimized and the design modified accordingly. The implication of any design change was assessed by modifying the Phase 1 static analysis model. Design changes resulting as an outcome of the analysis were then incorporated into the styling and the package. With the performance targets met, styling and the Phase 2 package were frozen, and with a more detailed Phase 2 design, a new shell model for the structural performance analysis was created. Static analysis was then used to optimize the Chapter 1 - Page 5

19 Phase 2 design until the requirements were met and new crash analysis models were built. In the process of design optimization, which included material grade and thickness selection, both static analysis and crash analysis were performed with constantly updated models until the targets were met. Throughout this process, simultaneous engineering provided input from the tool and part suppliers, as well as from steel manufacturers, to ensure the manufacturing feasibility of the designed parts. As a result of the simultaneous engineering process, only minor design and tool changes were needed after the drawings were released. When the first part set was completed, a workhorse (test unit) was built. The validation of the test unit lead to further part optimization and, finally, to the build of demonstration structures. Suppliers At the start of the detail design process in Phase 2, suppliers for stamped and hydroformed parts were selected in order to be included in the simultaneous engineering process. Among the selection criteria were quality, experience, skills and location. Supplier flexibility and their willingness to explore new manufacturing methods, utilizing material grades rarely used in these applications and to push the envelope in the application of tailor welded blanks or in hydroforming technologies, were as important in the selection process as their cost competitiveness. Steel Materials Steel Grades Perhaps the most important factor in meeting the targets for mass and crash performance is high strength steel. More than 90% of the ULSAB structure utilizes high strength and ultra high strength steel. High strength steels are applied where the design is driven by crash and strength requirements. Ultra high strength steels with yield strength of more than 550 MPa are used for parts to provide additional strength for front and side impact. High strength and ultra high strength steel material specifications range from 210 to 800 MPa yield strength with a thickness range from Chapter 1 - Page 6

20 0.65 to 2 mm. With the restriction of lower elongation, different forming characteristics and greater spring back of high strength steels, material supplier support combined with forming simulations were important factors in meeting the challenges for the development of manufacturable part designs. Steel Sandwich Material The use of steel sandwich material has contributed to considerable mass savings. The sandwich material is made with a thermoplastic (polypropylene) core, with a thickness of 0.65 mm and is layered between two thin steel skins, each with a thickness of 0.14 mm and yield strength of 240 MPa for the spare tire tub and 140 MPa for the dash panel insert. The steel sandwich shares many of the same processing possibilities of sheet steel, such as deep drawing, shear cutting, drilling, bonding, and riveting. However, it cannot be welded. Parts manufactured from steel sandwich material can be up to 50% lighter than those made of sheet steel with similar dimensional and functional characteristics. The spare tire tub made of steel sandwich material is a pre-painted module that is preassembled with the spare tire and repair tools. The module is dropped into place and bonded to the structure during the final assembly of the vehicle. Another application of sandwich material is the dash panel insert, which is bolted and bonded into the body structure, during final vehicle assembly. Tailor Welded Blanks Tailor welded blanks enable the engineers to accurately locate the steel within the part precisely where its attributes are most needed, while at the same time allowing for the elimination of mass that does not contribute to performance. Other benefits of tailor welded blanks include the use of fewer parts, dies and joining operations, as well as improved dimensional accuracy through the reduction of assembly steps. Nearly half (45%) of the ULSAB demonstration hardware mass consists of parts manufactured using laser welded tailored blanks. Chapter 1 - Page 7

21 The best example of tailor welded blank usage is the body side outer panel. It employs a fully laser welded tailored blank with different thicknesses and grades of high strength steel. Careful placement of the seams in the tailor welded blank is critical in order to minimize mass and facilitate forming. This consideration was especially important in the body side outer panel because of its complexity and size, its use of high strength steels and the integration of the rear quarter panel with its Class A surface requirement. Mass reduction and the elimination of reinforcements were key goals in the development of this one-piece design. The consolidation of parts reduced mass and assembly steps. Hydroforming Tubular Hydroforming The use of hydroforming should be considered as one of the most significant manufacturing processes applied in the ULSAB program for part manufacturing. The hydroformed side roof rail represents a significant structural member in the ULSAB structure. The side roof rail distributes loads appearing in the structure during vehicle operation, and in the event of an impact, distributes loads from the top of the A-pillar along the roof into B and C-pillar and then into the rear of the structure. The hydroformed side roof rail reduces the total number of parts and optimizes available package space. The raw material used to manufacture the side roof rail is a laser welded, high-strength steel tube 1 mm thick with an outside diameter of 96 mm and a yield strength of 280 MPa. The design was optimized and analyzed for feasibility using forming simulation. Hydromechanical Sheet Forming The use of hydromechanical sheet forming was chosen for the roof panel for mass reduction reasons. This process provided the opportunity to manufacture the roof panel at a thinner material thickness and still achieve a work-hardening effect in the center area, where the degree of stretch is normally minimal and an increased material thickness is needed to meet dent resistance requirements. With hydro-mechanical sheet forming, this Chapter 1 - Page 8

22 work-hardening effect is achieved by using fluid pressure to pre-stretch the blanks in the opposite direction towards the punch. This plastic elongation causes a work-hardening effect in the center area of the blank. In the second step, the punch forms the panel towards controlled fluid pressure and because there is no metal-to-metal contact on the outer part surface, excellent part quality is achieved. The ULSAB roof panel is manufactured in 0.7 mm high strength steel with a yield strength of 210 MPa. Tooling All tools for stamped parts are soft tools made of materials such as kirksite and built to production intent standards. Tools used for hydroforming are hard tools made of steel. In both cases, part manufacturing tolerances and quality standards were the same as those used in high-volume production. DH Assembly Joining Technologies For the final assembly of the ULSAB structure, four types of joining technologies were applied. Spot welding is used for joining the majority of parts. Laser welding became necessary to join the hydroformed side roof rail to its mating parts. In addition, the rails in the front end structure are laser welded for improved structural performance. Laser welding in body structure assembly is already being used in mass production by many OEMs. The active gas metal arc welding (MAG) process, with its disadvantages, such as slow welding speed and relatively large heat impact zones, was kept to a minimum and used only in locations with no weld access for spot or laser welding. Bonding is used to join the sandwich parts that cannot be spot or laser welded into the structure. For the joining of the DH, about one-third fewer spot welds and significantly more laser welding is employed than for conventional body structures. Chapter 1 - Page 9

23 Assembly Sequence For the DH build, the assembly sequence uses two stage body side framing. The assembly sequence includes underbody assembly, body side assemblies, roof and rear panel assemblies. All DHs were built in a single build sequence. Assembly Fixtures To assemble the DH, a modular fixture system was used. The fixtures were developed in a CAD system and the positions of locator holes were then incorporated into the parts design. DH Testing Testing was performed on the ULSAB test unit structure to validate its structural performance and mass. Included were tests for static torsion rigidity, static bending rigidity, modal analysis and mass in various configurations, including some bolt-on parts. Testing was performed at Porsche s Research & Development Center in Weissach, Germany. Physical testing for crash was not part of the ULSAB program in Phase 2 and may be performed in a possible Phase 3, after the necessary components are built and/or assembled into the ULSAB structure. Economic Analysis With the detailed information created in Phase 2 of the ULSAB program, the costs of parts and assembly of the body structure were analyzed. Under the management of a PES team, and with support from the ULSAB Consortium members, an economic analysis group, comprising of analysts from the Massachusetts Institute of Technology (MIT), IBIS Associates and Classic Design, a detailed cost model was constructed that includes all aspects of fabrication and assembly. This cost model will enable the automotive OEMs to calculate ULSAB cost based on their own manufacturing criteria. Considering that the focus of Phase 2 was on mass reduction and not on cost savings, the result of this cost analysis is quite remarkable. It confirms that significant mass reduction of the body structure, in Chapter 1 - Page 10

24 comparision to the benchmark vehicle average mass, was achieved with the use of steel with no cost penalty. Summary/Conclusion Throughout Phase 2, timely execution of the program was critical. All parts designed and released to our suppliers and all tooling and assembly of the first test unit have been on schedule. With the data acquired from the validation of the first test unit and subsequent testing, parts were refined and design optimization was performed. Refined parts were then used to build the demonstration hardware. Based on the testing of the demonstration hardware, the ULSAB structure shows Performance* Target Results Mass [ 200 kg 203 kg Static torsional rigidity m Nm/deg Nm/deg Static bending rigidity m12200 N/mm N/mm First body structure mode m 40 Hz 60 Hz *Structural performances are test results with glass. ULSAB structure mass without glass the following structural performances: Achieving these results in a timely manner could only be achieved by utilizing the team approach that involved all parties in the early stages of the ULSAB program. A close working relationship with the ULSAB Consortium members and the commitment of our suppliers and their enthusiasm for the program helped to meet the challenge of manufacturing parts made of steel materials and combinations that have not been commonly applied previously. This pioneering spirit was carried on by all members of the PES team, including designers and engineers. The ULSAB program has explored the potential for mass reduction in the body structure using steel as the chosen material. State-of-the-art manufacturing and joining technologies, such as laser welding in assembly and hydroforming as well as commercially available materials, contributed to the success of the ULSAB program. It proves that steel offers the potential for light weight vehicle design which contributes to the preservation of resources and the reduction of emissions. Based on this experience, the steel industry should further intensify its dialogue and cooperation with OEMs to achieve their common goal of mass reduction of tomorrow s vehicles, to protect the environment and to secure mobility of future generations. Chapter 1 - Page 11

25 2. Phase 2 Introduction Engineering Services, Inc.

26 2. Phase 2 Introduction 2.1. Phase 2 Program Goal The program goal of Phase 2 was the validation of Phase 1 results and the build of demonstration hardware. Phase 1 was the concept phase and consisted of concept design and analysis. The design was basic wire frame and surface data, without holes for drainage or locators for assembly. The Phase 1 analysis, based on the design concept, was meshed in its basic form to reflect the surfaces of the structure Phase 2 Design and Analysis The design in Phase 2 was a refinement of the Phase 1 design. It includes surface data, allowing for production of tools including principal location points (PLP) and holes for tooling, drainage and weld access. Additionally, refinement of the design for manufacture and assembly (DFMA) was developed as the final design progressed, with emphasis on mass production (more than 100,000 units per year). The intention in Phase 2 was to continue the development of a generic structure that takes into consideration manufacturing and assembly methods. With the detailed design of the structural components, and assemblies, and with materials selected, build specifications and the final assembly sequence were established. Chapter 2 - Page 1

27 Computer Aided Engineering (CAE) continued in Phase 2 in conjunction with the refinement of the design. The analysis provided confirmation of the design as well as structural and crash performance. The CAE analysis in Phase 2 included: Finite Element Model Modification Structural Analysis consisting of: w Mass w Static Torsion w Static Bending w Modal Analysis Continuing development of crash simulation concentrates on: AMS, 50% frontal offset crash at 55 km/h NCAP, 100% frontal crash at 35 mph (FMVSS 208) Side impact crash at 50 km/h (96/27 EG, with deformable barrier) Rear moving barrier crash at 35 mph (FMVSS 301) Roof crush (FMVSS 216) All models were continuously updated to compare Phase 2 and Phase 1 results in order to maintain the same performance standards Demonstration Hardware (DH) The term demonstration hardware is used to emphasize that the body structure is not a prototype but a legitimate representation of a production unit. All demonstration hardware components had to be fully tooled (soft tools for stamping and hard tools for hydroforming). All demonstration hardware was built in a single build sequence. The completed structure had to be clear-coat painted for unrestricted view of the build and construction methods. Chapter 2 - Page 2

28 2.4. Scope of Work Porsche Engineering Services, Inc. in Troy, Michigan executed the program. The DH build, testing and the CAE analysis was performed at the Porsche R & D Center in Weissach, Germany. To achieve the targets for performance, timing and cost, the program responsibilities of PES included the following tasks: Program Management and Planning Build Management for the Construction of the Demonstration Hardware Build of Demonstration Hardware Part Supplier/Manufacturer Evaluation and Selection Component Structure Design and Engineering CAE Analysis Physical Testing of Test Unit Economic Analysis Study Final Program Report 2.5. Materials The ULSAB Consortium member companies provided all material-specific data required to design, develop and construct the ULSAB body structure in Phase 2. All materials used to manufacture parts for the DH build were provided to Porsche by ULSAB Consortium member companies including the tailor welded blanks and raw material (tubes) for the manufacturing of the hydroform side roof rail. In addition, the individual ULSAB Consortium member companies supported the program with data related to material selection and tailor welded blank development, as well as forming simulation and circle grid analysis on selected parts in order to create a feasible part design. Chapter 2 - Page 3

29 2.6. Testing of Test Unit Physical testing was undertaken on the test unit to provide data and allow correlation of the CAE results with regard to: Mass Static Torsion Static Bending Modal Analysis Physical crash testing was not part of Phase 2. This could be executed in a possible Phase 3, with the necessary components, such as suspension, powertrain, and interior available Phase 2 Program Timing Prior to the start of Phase 2 the program timing was established and the various tasks assigned. Based on this timeline the ULSAB Consortium established specific information release dates to keep Chapter 2 - Page 4

30 ULSAB Phase 2 Program Timeline Task Name Package Refinement Styling (CAS) Class A Surfacing Design & Engineering Economic Analysis CAE Analysis Design Changes CAE Analysis (Iteration 1) Design Changes CAE Analysis (Iteration 2) Design Changes CAE Analysis (Iteration 3) Release Long Lead Items Tooling Test Unit Build Testing Design Changes CAE Validation Tooling Adjustments DH Build Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Chapter 2 - Page 5

31 3. ULSAB Phase 2 Package

32 3. ULSAB Phase 2 Package 3.1. General Approach Discussions with OEMs about Phase 1 findings provided valuable input and guidance for the more detailed Phase 2 package layout created at the start of Phase 2. The Phase 2 package was defined as a modification of the Phase 1 package without being too specific so the package findings could apply to more than one body structure concept. The most important components, space definitions and dimensions had to be considered by either defining them using engineering judgment, or by using actual component dimensions. Furthermore, secondary mass savings were not considered in order to take a more conservative and more credible approach. This is also reflected in component size and mass, as well as in the crash mass used for the crash analysis Package Definition The first step in the package phase was to define the vehicle concept type, exterior dimensions, interior dimensions and the main components. With these package definitions, package drawings were revised and structural hard points defined Vehicle Concept Type In Phase 2 the same concept type definition was used as in Phase 1, five passenger and four door midsize sedan. Chapter 3 - Page 1

33 Exterior Dimensions Ident.* Definition Measurements W101 Tread - front 1560 mm W102 Tread - rear 1545 mm W103 Vehicle width 1819 mm W117 Body width at SgRP - front 1767 mm L101 Wheelbase 2700 mm L103 Vehicle length 4714 mm L104 Overhang - front 940 mm L105 Overhang - rear 1074 mm L114 Front wheel centerline to front SgRP 1447 mm L123 Upper structure length 2631 mm L125 Cowl point - X coordinate 2016 mm L126 Front end length 1281 mm L127 Rear wheel centerline - X coordinate 4295 mm L128 Front wheel centerline - X coordinate 1595 mm L129 Rear end length 654 mm H101 Vehicle height 1453 mm H106 Angle of approach 14 H107 Angle of departure 15 H114 Cowl point to ground 1001 mm H121 Backlight slope angle 61 H122 Windshield slope angle 59 H124 Vision angle to windshield upper DLO 15 H136 Zero Z plane to ground - front 112 mm H138 Deck point to ground 1091 mm H152 Exhaust system to ground 170 mm H154 Fuel tank to ground 188 mm H155 Spare tire well to ground 311 mm *SAE J1100 Revised May 95 Chapter 3 - Page 2

34 Interior Dimensions Ident.* Definition Measurements W3 Shoulder room - front 1512 mm W4 Shoulder room - second 1522 mm W5 Hip room - front 1544 mm W6 Hip room - second 1544 mm W7 Steering wheel center - Y coordinate 350 mm W9 Steering wheel maximum outside diameter 370 mm W20 SgRP - front - Y coordinate 350 mm W25 SgRP - second - Y coordinate 335 mm W27 Head clearance diagonal - driver 79 mm W33 Head clearance diagonal - second 83 mm W35 Head clearance lateral - driver 136 mm W36 Head clearance lateral - second 132 mm L7 Steering wheel torso clearance 418 mm L11 Accelerator heel point to steering wheel center 412 mm L13 Brake pedal knee clearance 573 mm L30 Front of dash - X coordinate 1942 mm L32 SgRP - second to rear wheel centerline 473 mm L34 Effective leg room - front 1043 mm L38 Head clearance to windshield garnish - driver 266 mm L39 Head clearance to backlite garnish 21 mm L40 Torso (back) angle - front 25 L41 Torso (back) angle - second 25 L42 Hip angle - front 93 L43 Hip angle - second 86 L44 Knee angle - front 118 L45 Knee angle - second 88 L46 Foot angle - front 78 L47 Foot angle - second 113 L50 SgRP couple distance 780 mm L51 Effective leg room - second 894 mm L52 Brake pedal to accelerator 48 mm L53 SgRP - front to heel 832 mm *SAE J1100 Revised May 95 Chapter 3 - Page 3

35 Interior Dimensions (Cont d) Ident.* Definition Measurements H5 SgRP - front to ground 519 mm H6 SgRP - front to windshield lower DLO 495 mm H10 SgRP - second to ground 529 mm H11 Entrance height - front 798 mm H12 Entrance height - second 810 mm H13 Steering wheel to centerline of thigh 67 mm H14 Eyellipse to bottom of inside rearview mirror 40 mm H17 Accelerator heel point to steering wheel center 645 mm H18 Steering wheel angle 23 H25 Belt height - front 446 mm H26 Interior body height - front at zero Y plane 1011 mm H27 Interior body height - front at SgRP Y plane 1220 mm H29 Interior body height - second at SgRP Y plane 1033 mm H30 SgRP - front to heel 245 mm H31 SgRP - second to heel 303 mm H32 Cushion deflection - front 49 mm H33 Cushion deflection - second 66 mm H35 Vertical head clearance - driver 75 mm H36 Head clearance vertical - second 49 mm H37 Headlining to roof panel - front 7 mm H38 Headlining to roof panel - second 7 mm H40 Steering wheel to accelerator heel point 468 mm *SAE J1100 Revised May 95 Chapter 3 - Page 4

36 Interior Dimensions (Cont d) Ident.* Definition Measurements H41 Minimum head clearance - driver 88 mm H42 Minimum head clearance - second 21 mm H49 Eyellipse to top of steering wheel 17 mm H50 Upper-body opening to ground - front 1317 mm H51 Upper-body opening to ground - second 1339 mm H53 D-point - front to heel 137 mm H54 D-point - center passenger - front to tunnel 105 mm H55 D-point - center passenger - second to tunnel 43 mm H56 D-point - front to floor 182 mm H57 D-point - second to floor 72 mm H60 D-point to heel point - second 19 mm H61 Effective head room - front 1019 mm H63 Effective head room - second 972 mm H64 SgRP - front to windshield upper DLO 796 mm H69 Exit height - second 743 mm H70 SgRP - front - Z coordinate 631 mm H71 SgRp - second - Z coordinate 641 mm H75 Effective T-point head room - front 994 mm H76 Effective T-point head room - second 932 mm H77 Seatback height - front 868 mm H78 Seatback height - second 781 mm H94 Steering wheel to cushion - minimum 223 mm *SAE J1100 Revised May 95 Chapter 3 - Page 5

37 Main Component Definition Component Description Remarks Engine V6 Average size ~3000 ccm Engine Mounts Total of 3 2 on top of front rail 1 on subframe Radiator Size m With single fan Single routing, Vol 2.8 catalytic converter Exhaust System 1 catalytic converter, 21 ltr. muffler, LHS 1 muffler Battery L x W x H 280mm x 170mm x 170 mm LHS front of engine compartment Drive Train Transverse front wheel drive Transmission Automatic - manual G-shift for manual included in package Suspension Type, Front McPherson Mounted to front subframe Suspension Type, Rear Twist beam With separate spring shock absorber Tire Size Front-Rear 195/60R15 Winter tires 185/60R15 Spare Tire Space saver Tub to fit full size tire Fuel Tank volume ~65 ltr Located under rear seat Fuel Filler On RHS Routing in package Bumper Front-Rear Bolt-on Crash boxes included Steering Rack & pinion Steering rack housing on top of crossmember dash Cargo Volume 490 ltr VDA method with 200 x 100 x 50 mm module Hinges Similar to Porsche 911 / Boxster Weld through type Head Lamps Part of front end module Interior Front and rear seat concept In package drawing Cockpit Basic concept with I/P beam In package drawing Pedals Unit with integrated In package drawing foot-parking-brake Chapter 3 - Page 6

38 Underfloor Clearance The underfloor clearance of a vehicle depends on the vehicle load. The determination of the underfloor clearance relative to the road surface was crucial for the body structure design, styling, selection of components and their positioning in the vehicle structure. Underfloor clearance is defined as the summary of five different parameters. These are: Curb Clearance Front / Rear Angle of Approach / Departure Ramp Brakeover Angle Oil Pan Clearance Ground Clearance To define these parameters, three vehicle positions, which then depended on three specific load cases, needed to be determined. The three load cases applied to the vehicle were: Curb weight: The weight of a vehicle equipped for normal driving conditions. This includes fluids such as coolant, lubricants and a fuel tank filled to a minimum of 90%. Also included are the spare tire, tool kit, and car jack. Design weight: Vehicle curb weight plus the weight of three passengers (68 kg each, with luggage 7 kg each) with 2 passengers in the front seat and 1 passenger in the rear seat. Gross vehicle weight: Vehicle curb weight plus maximum payload (5 passengers plus luggage). Chapter 3 - Page 7

39 To determine the vehicle position relative to the road surface under these load conditions, the vehicle is positioned relative to zero grid Z-plane. Z R1 A R2 B Ground Figure ULSAB Vehicle Position Relative to Zero Grid Z-Plane X Using the ULSAB data and the weights of the three load cases, the road surface positions relative to the zero grid Z-plane and to the vehicle were calculated. ULSAB Data Number of Seats 5 Wheelbase Tires Pressure Front Rear Front Rear 2700 mm 195/60-R15 195/60-R bar 2.5 bar Calculation of Road Surface Positions Relative to the Vehicle Distance from Static Tire Load Case Zero Grid Z-Plane Radius Weight A (mm) B (mm) R1 (mm) R2 (mm) Curb Weight kg Design Weight kg Gross Vehicle Weight kg Chapter 3 - Page 8

40 Gross Vehicle Weight Design Weight Curb Weight Figure Road Surface Relative to Vehicle With the road surface positions relative to the vehicle, the underfloor clearance was determined. 190 mm Design Weight Gross Vehicle Weight 170 mm Figure Curb Clearance Front/Rear 14º Design Weight 15º Figure Angle of Approach/Departure Chapter 3 - Page 9

41 14º Gross Vehicle Weight Figure Ramp Breakover Angle 185 mm Design Weight Figure Oil Pan Clearance 143 mm Figure Ground Clearance Gross Vehicle Weight Chapter 3 - Page 10

42 Seating Position At first the 2-D manikins (spelling taken from SAE) were aligned in a comfortable seating position taking into consideration the angles between joints such as hip, knee, and foot. When the seating position was defined, verification was made that the operating parts like steering wheel, gearshift lever and pedal were in reach. This was important for ergonomic reasons. Two types of 2-D manikins were used: The small female, 5th percentile with a height of cm; and the tall male, 95th percentile with a height of cm. (5th percentile means that 5% of the population is smaller or equal in size and 95% is taller. 95th percentile means that 95% of the population is smaller or equal in size and 5% is taller.) For the dash panel layout the tall male 2-D manikin was used because it is more difficult to reach, since the seat position of the taller person is more rearward than it is for a shorter person. Figure Distance to Operating Parts of the 5% Female and the 95% Male Chapter 3 - Page 11

43 Visibility Study Horizontal and Vertical Obstruction For the study of horizontal, vertical and A-pillar obstruction of the driver s visibility, the following positions needed to be defined: Seating Reference Point (SgRP) It was necessary to determine the seating reference point (SgRP) in order to position the eyellipse (spelling taken from SAE) template and the eyepoints V1 / V2. For adjustable seats, the SgRP is defined as the hippoint (H-Point) relative to the driving seat in its most rearward position. The H-point is defined as the pivot center of the torso and thigh center lines. Eyellipse Eyepoints V1, V2 Torso Line Thigh Centerline SgR-Point Accelerator Heel Point Figure SgRP, Eyellipse, Eyepoints Eyellipse (SAE J941) The eyellipse is a tool to describe the vision of a driver. The template with the eyellipse is positioned with its horizontal reference line 635 mm above the SgRP and with the vertical reference line through the SgRP. Two types of templates, with two eyellipses, take the different seat track travel Chapter 3 - Page 12

44 ranges into consideration. For the ULSAB vehicle, with a seat track travel of 240 mm, a template for seat track travel of more than 130 mm was used. Eye Points V1 / V2 (RREG 77/649) The coordinates of the eye points V1 / V2 relative to the SgRP were determined by using the following dimensions: Point X Y Z V V Using vision lines through the eye points, the following vision areas are described: Traffic Light Vision Angle min. 14º Wiperfield Angle 10º Transparent Windscreen Area 7º Through V1 (77/649/EWG) Horizont View Through V1 V1 Steering Wheel Rim Obscuration 1º Through V2 (77/649/EWG) Unobstructedd Vision 4º Through V2 (77/649/EWG) Transparent Windscreen Area 5º Through V2 (77/649/EWG) V2 Figure Horizontal Vision Chapter 3 - Page 13

45 Vision Area A 20º (78/ /EWG) Vision Area B 17º (78/ /EWG) V1, V2 Y X Vision Area A 13º (78/ /EWG) Vision Area B 17º (78/ /EWG) Figure Vertical Vision A-Pillar Obstruction In order to determine the A-pillar obstruction, points P1 and P2 have to be determined first. The coordinates for these points related to the SgR-point are: Point X Y Z P1 35 mm -20 mm 627 mm P2 63 mm 47 mm 627 mm The ULSAB structure has a seat track travel of 240 mm. Therefore the X-value has to be corrected by -48 mm. Since the torso back angle is 25 degrees, no further correction is necessary for the X-value and Z-value. The new coordinates for the P-points are: Point X Y Z P1-13 mm -20 mm 627 mm P2 +15 mm 47 mm 627 mm Chapter 3 - Page 14

46 Y P2 +15 mm SgRP Pm +47 mm Horizontal Line -20 mm P1-13 mm X Figure Distance of the P-Points Relative to the SgR-Point Two planes are cutting the A-pillar in an angle of 2 and 5 degrees. In the front most intersection, the horizontal planes S1 and S2 cut the A-pillar (Figure ). 2º S2 S1 S2 S1 Pm 5º 627 mm SgRP Figure Determination of the Sections S1 and S2 Chapter 3 - Page 15

47 The sections in the plan view are shown in Figure P2 Pm P1 V1, V2 S2 S1 Figure Sections S1 and S2 in Plan View The point P1 is necessary to determine the A-pillar obscuration for the left side (for a left hand drive vehicle). P2 is necessary for the right side. If P1 fulfills the requirements, it is not necessary to determine the obscuration for the right A-pillar, since the right pillar is farther away from the driver. The template to determine the obstruction is shown in Figure P1 E2 104 mm 65 mm E1 Section S1 Inner Section S2 Outer α Figure Template for A-Pillar Obstruction Chapter 3 - Page 16

48 The point P1 on the template is aligned to the point P1 on the drawing. The line Section S2 Outer is laid tangent to the most outer edge of the A-pillar section (S2), including trim, door frame and door seal. The second tangent line Section S1 inner is laid to the most inner edge of the A-pillar section (S1), including trim, seal and dot matrix. (Figure ). P1 1º Figure Template in Position Gear Shift Lever Postion The position of the gearshift lever depends on the SgRP-position and on the torso back angle. The position of the gearshift lever in the side view is shown in Figure mm 290 mm 340 mm Figure Distance of Gearshift Lever Relative to SgR-Point Chapter 3 - Page 17

49 Pedal Position 98 mm 50 mm (Clutch) 48 mm (Brake) 58 mm 59 mm 53 mm 203 mm Seating Reference Point 201 mm 53 mm 89 mm Figure Pedal Position Side Figure Pedal Position Rear Bumper Height Definition ECE R42 for the bumper height definition requires a pendulum 445 mm above the curb weight vehicle position and the design weight vehicle position. At the same time an overlapping of 35 mm of the pendulum to the bumper is required. C D A B Figure Pendulum in the Extreme Height Position Chapter 3 - Page 18

50 A: Lower edge of the pendulum in the most upper level to the curb weight vehicle position. B: Upper edge of the pendulum in the most lower level to the design weight vehicle position. C: Overlapping of the pendulum to the bumper in extreme high position. D: Overlapping of the pendulum to the bumper in extreme low position. A B C D Front 467 mm 431 mm 91 mm 40 mm Rear 467 mm 402 mm 89 mm 38 mm Chapter 3 - Page 19

51 3.3. Package Drawings Since package drawings are orthographic projections of the vehicle contour in side view, plan view, front view and rear view, these views include all essential parts of the interior such as seats, seat position, seating reference point (SgRP), operating parts and the door openings. To define the interior of the vehicle including the seat position, visibility, and obstruction by the pillars, roof, hood and deck lid positions were determined. It was also important to define positions of the steering wheel, pedals, and gearshift lever. Other criteria were visibility to the instrument panel, and head clearance to the front, top and side. In the engine compartment, the engine, gearbox, exhaust system, radiator and battery were used in defining the space for the structural members of the front body structure. Components such as the fuel tank with the fuel filler system, the catalytic converter and exhaust system, and spare tire tub were also included in the package drawings. The package drawings were the starting point for the Phase 2 design. Chapter 3 - Page 20

52 Side View Figure Packing Drawing Side View Chapter 3 - Page 21

53 Plan View Figure Package drawing Plan View Chapter 3 - Page 22

54 Front and Rear View Figure Package Drawing Front View Figure Package Drawing Rear View Chapter 3 - Page 23

55 4. Styling Engineering Services, Inc.

56 4. Styling 4.1. Approach The Phase 1 concept design of the ULSAB program did not account for any Class A surfaces for the outer panels of the structure. To establish Class A surfaces in Phase 2, a complete styling of the ULSAB vehicle was necessary in order to create the surfaces of the roof panel, body side outer panel, the back light and the windshield. Styling also provided the major feature lines for the doors, deck lid, hood, fender and front and rear bumpers; these were needed for the development of the mating structural parts. For Phase 2, styling also gave the ULSAB structure a professional look and provided surfaces for further design studies in the future, i.e. on hoods, doors, deck lids, etc. The styling was developed electronically using CAS (computer aided styling), no clay models were used. With support from Porsche s styling studio, PES selected A. D. Concepts, a local source, to carry out the computer aided styling in a simultaneous engineering approach with PES. At the first team meetings of PES and A. D. Concepts, several elements of the styling were discussed with a view to creating a 3-dimensional styling model. Using the package drawings, important criteria such as overall vehicle proportions, vision lines, bumper locations and proposed cut lines were specified. After the initial meetings, a clearly defined vehicle architecture had evolved D Styling Phase Sketching In a team review of the first sketches, a neutral styling approach was chosen to ensure the ULSAB styling model would not be too futuristic or radical. Traditional sketching techniques were used along with the latest electronic paint sketching software from the Alias Wavefront company entitled StudioPaint running on Silicon Graphics High Impact workstations. Many automotive design studios around the world use this combination of hardware and software. The use of this tool for such a project increased productivity and enhanced the overall styling presentation with professionalism and accuracy, producing tighter sketches and more realistic, achievable styling goals. Chapter 4 - Page 1

57 Figure Styling Sketches Chapter 4 - Page 2

58 Clinic In the first clinic, dozens of sketches were reviewed by the design and styling team to determine which direction the styling would take prior to its presentation to the ULSAB Consortium. With the best sketches selected, five separate side view proposals and several different front and rear end treatments were developed. Figure Side View Proposal Electronic Paint In the studio, the CATIA package data was imported into a 3-D conceptual modeling software, called CDRS, and a side view outline drawing was developed for sketching purposes. The drawing was imported into StudioPaint and the five, very disciplined, side view sketch proposals (A-E) along with front and rear end sketch proposals were developed. Chapter 4 - Page 3

59 Styling Theme Selection The final styling theme selection was made during a meeting of the ULSAB Consortium s editorial group, together with PES and A. D. Concepts. In a secret ballot, the editorial group members from all around the world selected styling theme A. With the selection of the specific front and rear end treatments for the 3-D model, the 2-D phase of the ULSAB styling reached its conclusion. Figure Selected Styling Theme A Figure Styling Theme B Chapter 4 - Page 4

60 Figure Styling Theme C Figure Styling Theme D Figure Styling Theme E Chapter 4 - Page 5

61 Figure Selected Front View Proposal Figure Selected Rear View Proposal Chapter 4 - Page 6

62 D Styling Model To create the 3-D styling model, the package data was imported into CDRS along with the selected theme drawing and then the first phase of the 3-D model commenced. Side view lines, created using 2-D spine curves, were developed to represent the major feature lines of the vehicle. Typical sections at specific X locations were constructed. This data was reviewed by the design team to verify the positions of these major curves. The construction of the greenhouse, (the upper glass and roof surfaces of the vehicle), was started, transferring preliminary surfaces back and forth between CDRS and CATIA using an IGES translator. In the following Class A surfacing using CATIA, only subtle design changes were made to the CDRS surface model until both the styling and engineering teams were comfortable with the result. The release of the styling data by the styling team, in IGES file format, marked the first step in the 3-D modeling phase. Next, body side lines were constructed and surfaces were created. With the wheel openings, and the front and rear stance developed, the model started to take shape. The team developed the best proposal for front and rear door cut lines and this information was then incorporated into the CDRS styling model. After the front and rear end surfaces were completed, shaded tile images of the surface model were used to evaluate the forms. Highlight sections and surface curvature graphs were used to verify the aesthetic value of the model. Chapter 4 - Page 7

63 Surface Release Prior to the official surface release, the styling was reviewed to establish the exact location of all cut lines and shut lines. Shaded tile model images, with highlight reflection lines, were created in CDRS to allow both styling and engineering to discuss potential areas of concern. With the final release of the IGES surface model, the 3-D modeling phase was complete. Figure Surface Release 4.4. Rendering After the release of the surface model, the CDRS model was prepared for rendering. Model colors were selected in texture maps created to enhance the overall appearance of the photo realistic rendering. Neutral backgrounds and specific views were selected to create the first ULSAB styling images. To incorporate subtle engineering changes in the model, the CDRS 3-D models were revised and additional renderings were created. The models were enhanced further by the addition of texture maps for items such as license plate and rear window defrost. The 3-D model was imported back into StudioPaint 3-D to examine styling changes to the front and rear lamp treatments. These changes were then incorporated into the CDRS 3-D model and the final renderings completed, which concluded the styling phase. Chapter 4 - Page 8

64 Figure Figure Chapter 4 - Page 9

65 5. Design and Engineering

66 5. Design and Engineering 5.1. Phase 2 Design and Engineering Approach After the package was revised and the styling frozen, the challenge in Phase 2 was to maintain the structural performances, especially the mass, as analyzed in the Phase 1 concept. Further research into steel sandwich material led to additional changes in the Phase 2 design. Because of restrictions in size and application of the material, new design solutions had to be created to compensate for the advantages in mass reductions using sandwich material as it was applied in Phase 1. The hydroformed parts were analyzed for manufacturing feasibility using the detailed design data created in Phase 2. The restrictions of the hydroforming process, in combination with the refinement of the design, led to different concepts, design adjustments, and new solutions to achieve the target for mass. Furthermore, the 50% off-set crash, an additional crash analysis introduced in Phase 2, significantly influenced the design of parts, the application of steel grades, the material thicknesses and in particular, the changes to tailor welded blanks. Every change in the design process also had to be analyzed for its suitability for assembly and parts manufacturing. The design approach was driven by mass reduction and created innovative results without allowing initial component cost consideration to limit options. The design also focused on a production volume of more than 100,000 units per year. As well as concentrating on reaching the targets for performance and mass, importance was also placed on the reduction of assembly steps, the integration of reinforcements, the use of tailor welded blanks, and the avoidance of metal arc welding, wherever possible. Using the same design approach in both Phases 1 and 2, it was possible to maintain low mass and high structural performances. The Phase 1 design concept and approach, the flexibility of the concept and the potential that it could be adjusted to various design tasks, were challenged in Phase 2 and ultimately justified. Chapter 5 - Page 1

67 5.2. Design and Engineering Process The design and engineering process used in Phase 2 is shown in the flow chart (Fig ). All through this process, a simultaneous engineering approach was taken to find the best solutions to overcome the design and engineering challenges emerging in Phase 2. Start No Phase 1 Package/Concept Design Phase 2 Package Refinement Create Styling Concept Modify Package/ Styling / Design Modify Phase 1 Shell Model Meets Static Targets No No Modify Design Material / Thickness Adjustment Steel Supplier & Part Supplier Input Yes Meets Static/Crash Targets Create / Modify Phase 2 Crash Model Yes Meets Static Targets Create / Modify Phase 2 Shell Model Material / Thickness Selection, Design Modification Yes No No No No No No Parts Feasible Yes Yes Build of First Test Unit Meets Static / Crash Targets Yes Yes Build of Final Demonstration Hardware Figure Design and Engineering Process Using the Phase 1 package and concept design as the starting point, Phase 2 then refines the package. This refined Phase 2 package was the basis for the first styling layout, and in an interactive process, both were adjusted until the engineering requirements were met. The styling was frozen and the Phase 1 shell model was adjusted and analyzed using material thickness optimization to achieve Chapter 5 - Page 2

68 the mass target while maintaining the structural performance goals. Together with the selected suppliers and the Material Group of the ULSAB Consortium, the part design was discussed and the material thicknesses were selected. With this information, the design was revised and the Phase 2 shell model created, analyzed and modified until all targets were met. New Phase 2 crash analysis models were built and after the first analysis, design modifications, material grade and thickness selection, further crash analyses were performed, until the results were satisfactory. With the revised design and material selection, the shell model was updated and the static analysis performed. The crash and static analysis models were constantly updated as a result of information from tool, part and steel suppliers. This was repeated until all results were satisfactory. The design was then modified and the part drawings released to the suppliers. With the first part set delivered, a test unit was built and the tests following provided the results for static performance and most importantly for mass. The design was enhanced and material substituted as needed. The process of shell and crash model modifications and analysis was performed again to validate the design. After the final design was released to the suppliers, parts were manufactured and the demonstration hardware built. Part of this process included regular design review meetings (not shown in the flow chart) of the design and engineering team as well as design review meetings with the demonstration hardware build team, engineers and analysts at Porsche R & D Center in Germany. In these internal PES meetings, technical problems were discussed and design directions decided in order to prepare for the demonstration hardware build and meet established deadlines. Chapter 5 - Page 3

69 5.3. ULSAB Phase 2 Design Description Figure ULSAB Demonstration Hardware The ULSAB structure went through many adjustments and modifications in its transition from the Phase 1 concept to its final design stage at the end of Phase 2. This was due to added crash performance requirements, package issues, manufacturing processes and material application limitations. The exploded view (see Fig ) shows the demonstration hardware in the final Phase 2 design stage with the exception of minor brackets and reinforcements. Bolt-on parts and components, used in the analysis for crash performance, such as front and rear bumpers, engine, suspension, subframe, shock tower braces, tunnel bridge and fenders, are not considered part of the body structure and therefore are not shown in the exploded view. However, the structure is equipped with important brackets and reinforcements. Because tailor welded blanks can eliminate reinforcements, fewer were required. Included in the demonstration hardware, as shown on the exploded view, are the bolt-on front-end module and the dash-panel insert, including the brake booster reinforcement. Chapter 5 - Page 4

70 Parts List Demonstration Hardware The parts list (Fig ) corresponds directly with the exploded view of the demonstration hardware (Fig ) and shows the part name and number, the material grade, and thickness and the mass of the manufactured part. Parts listed that have two or more material thicknesses and grades indicate that this part is made from a tailor welded blank. The mass of the parts listed, is taken from actual manufactured parts, but does not represent an average of all parts manufactured. Therefore, the mass of the demonstration hardware can vary slightly in comparison to the listed mass of the total number of parts. Figure Demonstration Hardware Parts List Ma te ria l Ma te ria l Actua l Part Grade Thickness Part No Part Name (MPa) (mm) Mass (kg) 001 Assy Reinf Radiator Support Upper (Bolted on) Reinf Front Rail Extension RH Reinf Front Rail Extension LH A Assy Rail Front Outer RH B (Tailor Welded Blank) C A Assy Rail Front Outer LH B (Tailor Welded Blank) C A Assy Rail Front Inner RH B (Tailor Welded Blank) C A Assy Rail Front Inner LH B (Tailor Welded Blank) C Rail Front Extension RH Rail Front Extension LH Bracket Roof Rail Mount Low er RH Bracket Roof Rail Mount Low er LH Panel Dash Panel Dash Insert (Bolted on) Sandw ich Member Dash Front Panel Cow l Low er Panel Cow l Upper Assy Member Front Floor Support (2-Req'd) Assy Reinf Floor Front Seat Rear Outer (2-Req'd) Pan Front Floor Chapter 5 - Page 5

71 Figure Demonstration Hardware Parts List (Cont d) Ma te ria l Ma te ria l Actua l Part Grade Thickness Part No Part Name (MPa) (mm) Mass (kg) 042 A Panel Rocker Inner RH B (Tailor Welded Blank) A Panel Rocker Inner LH B (Tailor Welded Blank) Member Rear Suspension A Assy Rail Rear Inner RH B (Tailor Welded Blank) C A Assy Rail Rear Inner LH B (Tailor Welded Blank) C A Assy Rail Rear Outer RH B (Tailor Welded Blank) C A Assy Rail Rear Outer LH B (Tailor Welded Blank) C Panel Spare Tire Tub (Bonded on) Sandw ich Member Panel Back Panel Back A Panel Body Side Outer RH B (Tailor Welded Blank) C D E A Panel Body Side Outer LH B (Tailor Welded Blank) C D E Panel A-Pillar Inner Low er RH Panel A-Pillar Inner Low er LH Panel B-Pillar Inner RH Panel B-Pillar Inner LH Reinf B-Pillar Low er (2-Req'd) Panel Wheelhouse Inner RH Panel Wheelhouse Inner LH A Panel Wheelhouse Outer RH B (Tailor Welded Blank) A Panel Wheelhouse Outer LH B (Tailor Welded Blank) Chapter 5 - Page 6

72 Figure Demonstration Hardware Parts List (Cont d) Ma te ria l Ma te ria l Actua l Part Grade Thickness Part No Part Name (MPa) (mm) Mass (kg) 072 Rail Side Roof RH Rail Side Roof LH Panel A-Pillar Inner Upper RH Panel A-Pillar Inner Upper LH Panel Package Tray Upper Panel Package Tray Low er Support Package Tray RH Support Package Tray LH Panel Roof Panel Front Header Panel Rear Header Member Pass Through (2-Req'd) Member Kick Up Reinf Radiator Rail Closeout RH (Bolted on) Reinf Radiator Rail Closeout LH (Bolted on) A Panel Skirt RH B (Tailor Welded Blank) A Panel Skirt LH B (Tailor Welded Blank) Panel Gutter Decklid RH Panel Gutter Decklid LH Support Panel Rear Header RH Support Panel Rear Header LH Rail Fender Support Inner RH Rail Fender Support Inner LH Rail Fender Support Outer RH Rail Fender Support Outer LH Reinf Front Rail RH Reinf Front Rail LH Plate Rear Spring Upper (2-Req'd) Reinf Panel Dash Brake Booster (Bolted on) Assy Bracket Rear Shock Absorber Mount RH Assy Bracket Rear Shock Absorber Mount LH Reinf Floor Front Seat Rear Center Assy Reinf Rear Seat Inner Belt Mount (2-Req'd) Bracket Member Pass Through Low er (2-Req'd) Bracket Member Pass Through Upper Front Reinf Panel Dash Upper Pan Rear Floor Assy Reinf Hinge Decklid (2-Req'd) Reinf A-Pillar RH Chapter 5 - Page 7

73 Ma te ria l Ma te ria l Actua l Part Grade Thickness Part No Part Name (MPa) (mm) Mass (kg) 145 Reinf A-Pillar LH Bracket Member Pass Through Upper Rear Assy Closeout Fender Support Rail RH Assy Closeout Fender Support Rail LH Reinf Rail Dash RH Reinf Rail Dash LH Assy Reinf Cow l Low er Assy Hinge Door Upper RH (2-Req'd) Assy Hinge Door Low er RH (2-Req'd) Assy Hinge Door Upper LH (2-Req'd) Assy Hinge Door Low er LH (2-Req'd) Bracket Trailing Arm Mount RH Bracket Trailing Arm Mount LH Brace Radiator (2-Req'd) (Bolted on) Assy Reinf Seat Belt Retractor Rear (2-Req'd) Figure Demonstration Hardware Parts List (Cont d) Total Mass of Parts Chapter 5 - Page 8

74 * * * * * See Assemblies * * * * Figure ULSAB Phase 2 Exploded View Chapter 5 - Page 9

75 ULSAB Structure Mass For the Phase 1 concept, it was assumed that future average body structures would contain approximately 12 kg of brackets and reinforcements. This number can vary, up or down, depending on the type of vehicle, i.e., front or rear wheel drive, and the package of components. Since the goal of the ULSAB program is to provide solutions for a generic concept, it was assumed in Phase 1 that the 12 kg for brackets and reinforcements have to be considered in the calculation for mass to give the Phase 1 results more credibility. In Phase 1, the ULSAB structure was calculated with a mass of 193 kg. With the 12 kg for brackets and reinforcements, the total mass equals 205 kg. In Phase 2, some of the brackets and reinforcements are already welded into the structure. These are reflected accordingly in the mass of the demonstration hardware and also included in the parts list. With the refinement of the Phase 2 package, minor brackets and reinforcements were designed (but not manufactured) and their mass was calculated to get a more accurate determination than the general assumption used in Phase 1. These brackets and reinforcements represent a more generic, than detailed, selection. The selection was based on package information, chosen components and engineering judgment. It can be assumed that in a possible Phase 3, the number of brackets and reinforcements, and their actual mass when manufactured, can be insignificantly higher or lower. This depends on the final component selection; their position in the structure and efforts made to minimize their mass. Also included in the mass calculation are 100 weld studs. This also represents a generic number for this type of structure and is based on engineering judgment. The calculated mass of the ULSAB structure (Fig ) is the measured mass of the demonstration hardware parts and the calculated mass of brackets and reinforcements shown in Fig and Fig The ULSAB structure mass in Phase 2 is 203 kg, with the variation assumed to be +/- 1%. This low variation is due to each part being manufactured from one coil of steel. The differences in sheet thicknesses between coils do not apply for the demonstration hardware, but would have to be considered in mass production. ULSAB = Mass of Demonstration + Calculated Mass of Brackets Structure Mass Hardware (Parts) and Reinforcements kg = kg kg Figure Definition of ULSAB Structure Mass Chapter 5 - Page 10

76 Figure Designed Brackets not Manufactured but Considered Part of the ULSAB Structure Part No Name Qty Calc Mass [Kg] 331 Bracket Exhaust Mount /333 Bracket Engine Mount RH/LH /335 Bracket Fender Mount Rear RH/LH Bracket Battery Tray Bracket Spare Tire Mount /339 Bracket Fuel Tank Mount Rear RH/LH Bracket Front Tie Dow n Hook Bracket Rear Tie Dow n Hook /343 Bracket Front Jack Support RH/LH /345 Bracket Rear Jack Support RH/LH Bracket Plenum Support Center N/A Weld Studs ~ TOTAL Figure Designed Reinforcements not Manufactured but Considered Part of the ULSAB Structure Part No Name Qty Calc Mass [Kg] 310 Reinf Hood Hinge Mount Reinf Instrument Panel Beam Mount /313 Reinf Sub-Frame Front Mount /315 Reinf Sub-Frame Center Mount /317 Reinf Sub-Frame Rear Mount Reinf Steering Rack Assembly Mount RH Reinf Steering Rack Assembly Mount LH Reinf Gear Shift Mount Reinf Front Door Lock Striker Reinf Front Door Check Arm Reinf Rear Door Lock Striker Reinf Rear Door Check Arm Reinf Front D-Ring Adjustment Reinf Rear Seat Cushion Mount Reinf Rear Seat Latch Reinf Rear Seat Back Mount Outer Reinf Rear Seat Back Mount Center Reinf Deck Lid Latch TOTAL Chapter 5 - Page 11

77 ULSAB Demonstration Hardware Mass The mass of the demonstration hardware is kg. This reflects the total amount of the mass of one complete part set, including brackets, reinforcements and bolt-on parts, as measured. In Phase 1, nearly all brackets and reinforcements were included in the theoretical number of 12 kg and only a few were included in the Phase 1 concept design of the body structure. With the level of detail design in Phase 2 and the refined package, it was now possible to design and finally manufacture most of these brackets and reinforcements and weld or bolt them to the demonstration hardware. It was not the task in Phase 2 of the ULSAB program to design and to manufacture all brackets and reinforcements and therefore, the approach to concentrate only on the important ones was taken. The mass of these manufactured brackets, reinforcements and bolt-on parts is included in the demonstration hardware mass and listed in the parts list (Fig ). The parts are shown on the exploded view (Fig ). For easier identification, the extracted list from the parts list (Fig , -3 to Fig ) identifies these parts including their mass. The mass of the demonstration hardware as shown in Fig , consists of the mass of the pure body structure and the mass of brackets, reinforcements, bolt-on parts manufactured and welded or assembled to the body structure. Mass of Brackets, Reinforcements, Bolt-on Parts, DH Mass = Body Structure Mass + Welded and Assembled to the Body Structure kg = kg kg Figure Demonstration Hardware Mass Definition Chapter 5 - Page 12

78 Figure Reinforcements Manufactured and Welded to Structure Part No Name Qty Mass [Kg] 038 Assy Reinf Floor Front Seat Rear Outer Plate Rear Spring Upper Reinf Floor Front Seat Rear Center Reinf Rear Seat Inner Belt Mount Reinf Panel Dash Upper Assy Reinf Hinge Decklid Reinf A-Pillar RH Reinf A-Pillar LH Assy Closeout Fender Support Rail RH Assy Closeout Fender Support Rail LH Hinge Base RH Hinge Base LH Hinge Stem Hinge Stem Assy Reinf Cow l Low er Assy Reinf Seat Belt Retractor Rear parts Figure Brackets Manufactured and Welded to Structure Part No Name Qty Mass [Kg] 116 Assy Bracket Rear Shock Absorber Mount RH Assy Bracket Rear Shock Absorber Mount LH Bracket Trailing Arm Mount RH Bracket Trailing Arm Mount LH parts Figure Bolt-On Parts Manufactured and Attached to Structure Part No Name Qty Mass [Kg] 001 Assembly Reinf Radiator Support Upper Panel Dash Insert Reinf Radiator Rail Closeout RH Reinf Radiator Rail Closeout LH Reinf Panel Dash Brake Booster Brace Radiator parts Chapter 5 - Page 13

79 Mass of Brackets and Reinforcements Phase 2 The total mass of all brackets and reinforcements, (meaning the calculated mass of designed, not manufactured parts) and bolted-on parts welded or assembled to the demonstration hardware, amounts to 16.6 kg, and is included in the ULSAB structure mass of kg. Total Mass of Brackets, Reinforcements & Bolt-on Parts kg Calculated mass of brackets & reinforcements, not manufactured or part of the ULSAB Structure 6.4 kg 4.35 kg Bolt-on parts assembled to body structure 1.35 kg 4.5 kg Brackets welded to body structure Reinforcements welded to body structure Figure Mass Breakdown of Brackets, Reinforcements and Bolt-on Parts Chapter 5 - Page 14

80 ULSAB Structure Mass Comparison Phase 1 Phase 2 The comparison of the results of the ULSAB structure mass is shown in Fig In Phase 2 the measured body structure mass has decreased with the refinement of the design, compared with the body structure mass as calculated in Phase 1. The total calculated mass of 205 kg, as in the Phase 1 ULSAB structure, is compared to the Phase 2 ULSAB structure mass of kg, which includes the actual mass of the demonstration hardware plus the calculated mass of brackets and reinforcements. Assumed theoretical mass of brackets & reinforcements { Phase 1 Phase 2 12 kg 6.4 kg } } Calculated mass of brackets & reinforcements designed, not manufactured Brackets, reinforcements & bolt-on parts included in demonstration hardware (10.2 kg) Concept 193 kg Validation kg Body structure Mass Offset crash + Offset crash Package refinement + Package refinement Styling + Styling Body Structure Mass Mass of Demonstration Hardware ULSAB Structure Mass 205 kg ULSAB Structure Mass kg ± 1% Figure ULSAB Structure Mass Phase 1 - Phase 2 Chapter 5 - Page 15

81 DH Part Manufacturing Processes The ULSAB structure as developed during Phase 1 and refined in Phase 2 is in general, a unibody design, with the exception of the hydroformed side roof rails. Stamping was the main manufacturing process considered for the parts design. Relative to the body structure mass of kg, 89.2% is the mass of all stamped parts. The stampings can be divided into two groups; conventional stampings and stamped parts made from tailor welded blanks. 42.8% of the body structure mass is represented by conventionally stamped parts and 44.9% is the mass of parts made from tailor welded blanks. This relatively high percentage of tailor welded blank stampings, relative to the body structure mass, is one good indication of how the mass reduction was achieved. Especially if the use of high strength steels, in connection with the tailor welded blanks, is put into consideration. The hydroforming process is applied in the form of two processes: The tubular hydroforming process for the side roof rail manufacturing The hydromechanical sheet forming process, for the roof panel manufacturing. The spare tire tub and the dash panel insert are designed to be manufactured from steel sandwich material, also using the stamping process. Chapter 5 - Page 16

82 The mass of the stamped parts made from steel sandwich material is 1.5% relative to the overall mass. 1.5% are miscellaneous parts, stock materials, such as tubes, or the forged hinge base of the weld through hinges. The pie chart in Fig shows the mass distribution of the manufacturing processes relative to the DH mass. The process used to manufacture the parts is shown in Fig ÒÒÒ 89.2% Stampings ÒÒ 9.3% Hydroforming Parts Ò 1.5% Misc.(Stock Material) Parts 44.9% Tailor Welded Blank Stamping 42.8% Conventional Blank Stamping 1.5% Miscellaneous 1.5% Steel Sandwich Material Blank Stamping 4.9% Tubular Hydroforming 4.4% Sheet Hydroforming Figure Manufacturing Process Relative to DH Mass Chapter 5 - Page 17

83 * * * * Chapter 5 - Page 18 * * * * Part Manufacturing Process Ò Conventional Blank, Stamping Ò Tailor Welded Blank, Stamping Ò Sheet, Hydroforming Ò Tubular Hydroforming Ò Sandwich Material Blank, Stamping Ò Misc.(Stock Materials) * See Assemblies Figure ULSAB Manufacturing Processes of Demonstration Hardware Parts

84 Material Grades The selection of the steel grades is a result of the need for good crash performance and mass reduction. In Phase 2, the utilization of high strength steel is 91%, relative to the DH mass (Fig ) of Phase 1. The parts design had to consider the lower elongation, and together with the tool manufacturer, the parts design was optimized to accommodate the different forming characteristics and greater spring back of high and ultra high strength steels. This was most important for the design of the tailor welded blank stamped parts which where different grades and thicknesses of high strength steels and combined into one part. High strength and ultra high strength steel material was used on parts contributing to the crash management of the structure, i.e. front rails, rear rails, rocker, etc. (Fig ). With this approach, and in combination with tailor welded blanks, it was possible to avoid the need for reinforcements and thus reduced the total number of parts. For mass reduction, steel sandwich material was applied in the spare tire tub and the dash panel insert. Steel sandwich material contributes to 1.5% of the DH mass. Due to the overall design, material specifications of steel sandwich material and restrictions in its applications, such as low heat resistance and available size, this material s use was limited during Phase 2. Chapter 5 - Page 19

85 Mild Steel 7.6% High Strength Steels 90.9% Steel Sandwich Material 1.5% 45.1% MPa 13.5% MPa 27.1% MPa 2.7% MPa 7.6% MPa 1.5% - Steel Sandwich Material 2.5% - Ultra High Strength Steel > 550 MPa Figure Ò 140 MPa Ò 210 MPa Ò 280 MPa Ò 350 MPa Ò 420 MPa Ò > 550 MPa Ultra High Strength Steel Ò Steel Sandwich Material Chapter 5 - Page 20

86 * * * * Chapter 5 - Page 21 * * * * Figure Material Grades of DH Parts Ò 140 MPa Ò 210 MPa Ò 280 MPa Ò 350 MPa Ò 420 MPa Ò >550 MPa Ò Steel Sandwich Material * See Assemblies Engineering Services, Inc.

87 Material Thickness The distribution of the used material sheet thicknesses relative to the DH mass is shown in Fig The majority of the mass (25%) is made from 0.7 mm sheet steel. Parts with a large surface area such as the panel floor, the panel dash and the panel roof are manufactured of high strength steel of this thickness, and are parts with secondary influence in crash performance. All 1.3 mm thickness material is high strength steel with the yield strength ranging from 280 MPa (46%) to 350 MPa (54%). The parts made of 1.3 mm material used in conventional stampings and tailor welded blank stampings have primary influence on crash performance. Since the demonstration hardware mass consists of 91% high strength steel, nearly all parts are made from high strength steel sheets in a thickness ranging from 0.65mm to 2.0mm. Percent Distribution of Material Thickness Relative to DH Mass 25.1% 10.8% 10.9% 7.6% 9.1% 8.4% 7.6% 3.0% 0.8% 4.2% 2.1% 3.0% 4.4% 1.5% 1.5% Sandwich Misc Figure Material Thickness Chapter 5 - Page 22

88 5.4. Detail Design PES executed an entirely paperless design using Computer Aided Design (CAD) and CATIA software for the detail design. With the involvement of part suppliers in the United States and Europe, the Porsche R & D Center, in Germany, and the necessary data exchange for the tool development and the design of the assembly fixtures, this approach proved to be very efficient Weld Flange Standards For the detail parts design it was important to define standards for the design of the weld flanges. The decision was made not to reduce the weld flange width for mass reduction, which allowed the use of standard weld equipment for the demonstration hardware assembly Weld Flanges for Spot or Laser Welding For the design of parts to be spot welded, the flange length was designed to the Porsche standards shown in Fig For the laser welding in assembly, the same standards were applied. Figure ULSAB Spot Weld Standards Chapter 5 - Page 23

89 Scalloped Spot Weld Flanges Scalloped flanges were used for mass reduction. Figure Part no. 81 Panel Package Tray Lower with Scalloped Flanges The design is similar to the scalloped flanges used in production of the Porsche 911 and Boxster. The second reason for scalloping weld flanges was to create two sheet spot welding where three sheet spot welding would have been applied, otherwise. Scalloped flanges were applied to parts not critical for sealing and not sensitive to crash or durability. The mass reduction achieved with scalloped flanges on the selected parts, based on the calculated part mass equals 0.43 kg. (Fig ) The flange geometry is shown in Fig The layout for a two sheet weld flange and a three sheet weld flange with scalloped flanges is shown in Fig Chapter 5 - Page 24

90 Flange Geometry Figure Flange Geometry Two Sheet Weld Flange Three Sheet Weld Flange Figure Layout of 2 and 3 Sheet Weld Flanges Chapter 5 - Page 25

91 Part Number Part Name Calculated Part Mass [kg] Calculated Part Mass with Scalloped Flange [kg] Mass Reduction [kg] 21 Panel Dash Panel Cowl Lower Pan Front Floor Member Rear Suspension Member Panel Back Panel Wheelhouse Inner RH Panel Wheelhouse Inner LH Panel Package Tray Lower Pan Rear Floor Figure Mass Reduction with Scalloped Flanges Locator, Tooling and Electrophoresis Holes Included in the detail part design are all locator holes for the assembly. All locator holes needed for parts manufacturing and the holes necessary for the electrophoresis of the body structure. After the location of the holes for electrophoreses were first determined, they were then incorporated into the crash models and the crash analysis was performed to verify that their position did not have any negative influence on the crash performance. After this verification, the holes were incorporated into the parts design. Chapter 5 - Page 26

92 Design Refinement Phase 1 reflected a concept design. In Phase 2, the task was to make the design feasible for manufacturing of the parts to maintain low mass and structural performances and also, to achieve the crashworthiness of the structure. In the refinement of the design, changes to the design concept were done for the following reasons: Mass reduction Manufacturing and tooling Assembly Material specifications Crash performance Package Styling The overview of design changes as shown in Fig , names the parts or areas of the structure, the design change and the reason for the different solution or change from Phase 1 to Phase 2. Chapter 5 - Page 27

93 Overview of Major Design Changes in Phase 2 Part Part / Location Description Reason No. Area of Change for Change 1 Fender Support Rail 2 Pan Front & Pan Rear Floor 3 Rear Rails Hydroforming part was replaced with 2 part stamping 3 part front floor with sandwich material tunnel deleted Spring & shock absorber relocated with new rear suspension Assembly, part manufacturing Heat resistance of sandwich material not sufficient for bake hardening process Mass reduction, package 4 Front Rails Space between rails increased Package of bigger engine Rear part of the front wheelhouse deleted 5 Panel Skirt Redesigned, tailor welded blank 6 Panel Spare Tire Reinforcement shock tower deleted, integrated in new panel skirt Tub designed as separate module from steel sandwich material and to be bonded to the rear floor after final assembly Mass reduction Package of new front suspension in conjunction with #4 Mass reduction Heat resistance of sandwich material, not sufficient for bake hardening process 7 Package Tray Redesigned from 3 part to 2 part design roll formed member package Assembly tray front deleted 8 Member Dash Front, Member Front Floor Support, Member Kick-up Material changed from high strength to ultra high strength steel >550 MPa Front Crash, side impact crash yield strength 9 Panel Body Side Outer 10 B-Pillar Joint 11 A-Pillar - Cowl - Fender Support Rail-Hinge Pillar Joint 12 Panel Back Blank configuration in tailor welded blank with all blanks in high strength Crash analysis, mass reduction steels Rocker inner extended upwards into B-Pillar. B-Pillar lower reinforcement modified Joint modified 3 Piece design integrated into one part Side impact, crash assembly Assembly, revised fender support rail Mass reduction, assembly 13 Side Roof Rail Design refinements Manufacturing process - hydroforming 14 Bolt on Front End Welded Change in front end module concept Figure Chapter 5 - Page 28

94 6. CAE Analysis Results Engineering Services, Inc.

95 6. CAE Analysis Results 6.1. Selected Tests for CAE To verify that the ULSAB meets the targets set in the beginning of Phase 1, the following tests were chosen for the static and dynamic stiffness. Structural Performances Static torsion stiffness Static bending stiffness Normal modes (first modes) Targets Nm/deg N/mm 40 Hz Figure Load cases and targets for static and dynamic stiffness For analytical crash testing the following tests were selected: AMS, 50% frontal offset crash at 55 km/h NCAP, 100% frontal crash at 35 mph (FMVSS 208) Side impact crash at 50 km/h (96/27 EG, with deformable barrier) Rear moving barrier crash at 35 mph (FMVSS 301) Roof crush (FMVSS 216) 6.2. Static and Dynamic Stiffness Based on CAD surface data the FE-Model (Figure 6.2-1) for the body in white was created. Because of the structure symmetry, only a half model with certain boundary conditions at the symmetry plane at y=0 for the static and dynamic stiffness simulations were used. The stiffness model consists in triangle and quadrilateral elements. To connect the different structure components, different methods were used. To connect laser welded parts in the FE-Model, the nodes of the flanges were equivalent. For spot welded areas the middle flange nodes are connected with welding point elements. The weld point distance was with a point Chapter 6 - Page 1

96 distance of about 50 mm. The CAE configuration for the static and dynamic simulations consist of the following parts: Welded Body Structure Bonded Windshield and Back Light Bonded and bolted Panel Dash Insert (Part-No. 022) Bonded Panel Spare Tire Tub (Part-No. 050) Bolted Reinforcement Panel Dash Brake Booster (Part-No. 115) Bolted Braces Radiator (Part-No. 188) Bolted Reinforcement Radiator Rail Closeout RH/LH (Part -No. 094/095) Bolted Reinforcement Radiator Support Upper (Part-No. 001) Bolted Tunnel Bridge Lower/Upper Bolted Brace Cowl to Shock Tower Assembly Figure FE-Model The stiffness model (per half model) consisted of: shell elements nodes The deformed shapes for the load cases torsion and bending are shown in the Figures and To view the stiffness distribution vs. the x-axis, the diagrams (torsion) and (bending) are used. The derivation vs. the x-axis for torsion (Fig ) and bending (Fig ) as well as the strain energy contour plots (Fig and Fig ) show the sensitive areas. The colored areas of the strain plots show the elastic energy, which is a result of the Chapter 6 - Page 2

97 deformation stored in the structure, as internal energy. The deformed shape of the dynamic stiffness simulation, the normal modes are shown in the Figures to The deformed frequency mode belongs to the normal modes mentioned in Table CAE Structural Performance Static Torsional Stiffness Static Bending Stiffness CAE Mass* (with glass) CAE Mass* (without glass) First Torsion Mode First Bending Mode Front End Lateral Nm/deg N/mm kg kg 61.4 Hz 61.8 Hz 60.3 Hz *Mass as in test configuration (Chapter 6, page 2), brackets and reinforcements (6.4 kg) are not included (see Chapter 5, page 10) Figure Table of CAE Structural Performance Torsional Stiffness A load of 1000 N was applied at the shock tower front while the body structure was constrained at the rear center spring attachment in the lateral and vertical directions. Figure Deformed Shape for Torsion Chapter 6 - Page 3

98 Torsion Angle Nm/deg 0.08 Support Angle = atan (zdisp/ycoor) [deg] Shock Tower Front Figure Torsion Angle vs. x-axis Longitudinal X-axis [mm] Center, Spring Attachment Rear Derivation of Torsion Angle 0.03 Support 0.02 Derivation of Angle [deg/mm] Shock Tower Front Longitudinal X-axis [mm] Figure Derivation of Torsion Angle vs. x-axis Center, Spring Attachment Rear Chapter 6 - Page 4

99 Figure Strain Energy Contour Plot for Torsion Bending Stiffness The loads were applied to the center of the front seats and to the center of the two outer rear seats. The measurements were taken under a load of F max = 4000 N b (4 x 1000 N). Figure Deformed Shape for Bending Chapter 6 - Page 5

100 Vertical Z-Displacement N/mm 0.25 Support Vertical Z-Displacement [mm] Shock Tower Front Longitudinal X-Axis [mm] Figure z-displacement vs. x-axis, Bending Center, Spring Attachment Rear Derivation of Vertical Z-Displacement Derivation of vertical Z-Displacement [mm] Shock Tower Front Longitudinal X-Axis [mm] Center, Spring Attachment Rear Support Figure Derivation of z-displacement vs. x-axis, Bending Chapter 6 - Page 6

101 Figure Strain Energy Contour Plot for Bending Normal Modes Figure Front End Lateral Mode Chapter 6 - Page 7

102 Figure First Bending Mode Figure First Torsion Mode Chapter 6 - Page 8

103 6.3. Crash Analysis For three crash types of the ULSAB project, one common crash model was generated. With this model the crash simulations were conducted: AMS 50% frontal offset crash at 55 km/h NCAP 100% frontal crash FMVSS 208 at 35 mph Side impact crash at 50 km/h (96/27 EG with deformable barrier) For the rear crash (FMVSS 301) at 35mph only a half structure (Fig ) was used. Fig shows the high level of detail for the FE-Model. To realize a realistic crash behavior of the simulation, all the spot welds and laser welded areas were considered in the models. To analyze the crash behavior, all crash-relevant car components were modeled, such as: Wheels with tire model Engine and transmission Steering system Chassis system with subframe Fuel tank Bumper system including crashbox Radiator with fan Battery Spare tire Brake booster, ABS box and cylinder Doors, front and rear without glass The door concept used for all simulations was a typical two shell structure with an inner and outer panel, an upper door reinforcement and two high strength side impact beams at the front door and one side impact beam at the rear door. A three point fixture with reinforcements at the hinges and the locks supported the doors. To reduce the model size for the roof crush analysis, the full model with reduced contents was used (Fig ). Chapter 6 - Page 9

104 Figure Crash Analysis Model A high level of detail of the surfaces, welding and mounting locations was necessary to provide the resolution to be able to access the events. The LS-DYNA complete full model had elements and nodes. Chapter 6 - Page 10

105 The vehicle mass was defined to be base curb weight plus two 50 th percentile male dummies with 113 kg of luggage. The crash mass of the vehicle was set at 1612 kg. The crash mass of the vehicle is calculated as follows: Curb Mass Luggage Dummies Total Crash Mass 1350 kg 113 kg 149 kg 1612 kg AMS Offset Crash The AMS offset crash was defined in the year 1990 by the editor of the German automotive magazine Auto Motor Sport (AMS). The aim of this offset crash is to secure the passenger compartment residual space. For this requirement a stiff passenger compartment and a good energy absorption in the front structure is needed. The initial velocity for the car is 55 km/h for the AMS crash. The Offset barrier is a block with a 15 degree rotated contact area including two anti-slide devices mounted on the contact surface. The left side of the car hits the barrier with an overlap of 50%. For actual crash tests AMS analyzes the following values: HIC-value (Head Injury Criterion) Head, chest and pelvis acceleration Maximum belt forces Maximum femur forces Dynamic steering deformation Foot well intrusions Door opening after test Because the analysis did not include dummies, injury assessment could not be made. Injury performance is greatly affected by the structural crash and steering column movement as well as by the knee bar design. Evaluation of passenger compartment intrusion can be made by looking at deformation in the foot well area (Fig ). Looking at the overall shape of the deformation (Fig , -3 can assess structural integrity). Chapter 6 - Page 11

106 Figure AMS Offset Crash Analysis Setup The AMS Offset undeformed and deformed shapes are shown in Fig and The deformed shape in these figures is after 100 ms. The deformation in the footwell area is shown in Fig The analyzed deformation is measured in the foot well area where it is important to keep the deformations as low as possible, because of the injury of the passenger s legs. The internal energy absorption diagram in Fig gives an overview of the internal energy absorbed in the parts subframe, bumper beam, crashbox, front rail and fender side rail after 100 ms. The diagram in Fig shows the load path for the most important front structure components. The diagram shows the main load path is the rail front. The fender side rail and the subframe have about the same load level. The diagram, AMS Offset Crash Acceleration vs. Time (Fig ) shows an average acceleration calculated from the rocker LHS, tunnel, and rocker RHS. After the contact between AMS barrier and engine, a middle acceleration of about 25 g results in the passenger area. The Figure shows the function of the car deformation versus time. After about 90 ms the maximum dynamic deformation is reached. Chapter 6 - Page 12

107 t = 0 ms t = 100 ms Figure AMS Offset Crash Deformed Shapes t = 0 ms t = 100 ms Figure AMS Offset Crash Deformed Shapes of Longitudinals Chapter 6 - Page 13

108 Figure AMS Offset Crash Maximum Dynamic Foot Room Intrusion in mm Subframe 26.9 Bumper Beam 17.3 Crash Box 5.6 Rail Front 37.6 Fender S. Rail Energy (kj) Figure AMS Offset Crash Internal Energy Absorption Chapter 6 - Page 14

109 Subframe 55 Front Rail Ext. 50 Rocker 85 Rail Front 115 Fender S. Rail Force (kn) Figure AMS Offset Crash Typical Cross Section Forces Average Car Acceleration vs. Time Rocker LHS / Tunnel / Rocker RHS ax [g] time [ms] Figure AMS Offset Crash Acceleration vs. Time Chapter 6 - Page 15

110 Car Deformation vs. Time sx [mm] time [ms] Figure AMS Offset Crash Deformation vs. Time Chapter 6 - Page 16

111 In the following table (Fig ), the AMS crash events vs. time are explained: Time (ms) AMS Offset Crash Initial folding of longitudinal LHS Initial folding of subframe First buckling of rail upper in front of shock tower Wheel LHS contacts barrier Engine contacts barrier, start of vehicle-rotation around z-axis Deformable front end of the subframe totally deformed, stiffer rear end and the extension longitudinal LHS starts moving rearwards and causes deformation in the front floor area, buckling of the longitudinal in the area of the shock tower Second buckling of rail upper LHS behind the shock tower Buckling of the rear end of the subframe at the fixture on the extension longitudinals Buckling of the brace cowl to shock tower LHS. Engine hits the steering gear Contact between gearbox-mounting and brake booster Wheel LHS hits the hinge pillar Maximum dynamic deformation reached Figure AMS Offset Crash Events Chapter 6 - Page 17

112 This analysis shows good progressive crush on the barrier side (left), as well as crush on the right, indicating transfer of load to the right side of the structure. This transfer means that the barrier side is not relied upon solely to manage the crash event. This transfer also contributes to the preservation of the occupant compartment. The intrusion of 146 mm into the footwell is minimal given the severity of this event. The initial, early peak shown in the pulse graph should trigger air bag systems. Peak deceleration of approximately 35 gs, a good result considering the severity of this event. Chapter 6 - Page 18

113 NCAP 100% Frontal Crash The conditions for the front crash analysis are based on several requirements. In the ULSAB program, the focus was on progressive crush of the upper and lower load path, sequential stack up of the bumper, radiator, and powertrain, integrity between individual components, A-pillar displacement, definition of the door opening, uniform distribution of the load, toe pan intrusion, and passenger compartment residual space. These requirements contribute towards occupant safety and the United State Federal Motor Vehicle Safety Standard, FMVSS 208. The test sequence of the front crash analysis is set up to duplicate a 35 mph, National Highway and Traffic Safety Association (NHTSA) full frontal barrier test (Fig ). Figure NCAP 100% Crash Analysis Setup Chapter 6 - Page 19

114 The NCAP 100% Frontal Crash undeformed and deformed shape is shown in Figures and The deformed shape in the figure is after 100 ms. The deformation in the footwell area is shown in Fig The analyzed deformations are measured in the foot well area where it is important to keep the deformations as low as possible, because of the injury of the passenger legs. The internal energy absorption diagram in Fig gives an overview of the internal energy absorbed in the parts subframe, bumper beam, crashbox, front rail and fender side rail after 100 ms. The diagram in Fig shows the section force for the most important front structure components. The diagram shows that the main load path is the rail front. The components, fender side rail and the subframe have about the same load level. The diagram, NCAP Crash Acceleration vs. Time (Fig ), is an average of accelerations at the rocker LHS, tunnel, and rocker RHS. After the contact between barrier and engine it results a middle acceleration of about 29 g at the passenger area. The Figure shows the function of the car deformation versus time. After about 68 ms the maximum dynamic deformation is reached. t = 0 ms t = 100 ms Figure NCAP 100% Crash Deformed Shapes Chapter 6 - Page 20

115 t = 0 ms t = 100 ms Figure NCAP 100% Crash Deformed Shapes of Longitudinals Figure NCAP 100% Crash Maximum Dynamic Foot Room Intrusion in mm Chapter 6 - Page 21

116 Subframe 30 Rail Upper 12.5 Rail Front 55.3 Crash Box 8 Bumper Front Energy (kj) Figure NCAP 100% Crash Internal Energy Absorption Subframe 49 Rocker 50 Rail Upper 41 Rail Front 120 Front Rail Ext Force (kn) Figure NCAP 100% Crash Typical Cross Section Forces Chapter 6 - Page 22

117 Average Car Acceleration vs. Time Rocker LHS / Tunnel / Rocker RHS ax [g] time [ms] Figure NCAP 100% Crash Acceleration vs. Time Car Deformation vs. Time sx [mm] time [ms] Figure NCAP 100% Crash Deformation vs. Time Chapter 6 - Page 23

118 The following table (Figure ) shows the NCAP crash events: Time (ms) NCAP Front Crash Initial folding of longitudinal Initial folding of subframe First buckling of rails upper in front of shock tower Engine contacts barrier Buckling of the rear end of the subframe at the fixture on the extension longitudinals Rear end of longitudinals start to buckle behind the reinforcement (still stable) Wheels contacts barrier Maximum dynamic deformation reached Figure NCAP Front Crash Events This analysis illustrates good progressive crush of the upper and lower structure and subframe. It shows peak deceleration of 31 gs, which is satisfactory considering that this structure is designed with stiffer body sides to meet 50% AMS offset crash requirements. The pulse graph is sympathetic to current occupant restraint systems. It shows a consistent rise to the peak of 31 gs then a smooth ride down to zero, indicating that the occupant would experience controlled restraint. The initial, early peak should trigger air bag systems. Low intrusion at the footwell indicates that leg damage is unlikely. Chapter 6 - Page 24

119 Rear Crash The conditions for the rear impact analysis are based on the United States Rear Moving Barrier Test FMVSS-301. The test specifically addresses fuel system integrity during a rear impact. Automotive companies also include structural integrity and passenger compartment volume as additional goals for this test. The impacting barrier is designed to represent a worst case rear crash (Fig ). The rear crash barrier is a rigid body with a mass of 1830 kg, making contact at zero degrees relative to the stationary vehicle. The Federal Standard identifies that the velocity of the rear moving barrier is 30 mph. The ULSAB program has raised the standard to 35 mph, which is 36% more kinetic energy of the moving barrier. Evaluating fuel system integrity is done by representing a fuel tank system. The additional goals of passenger compartment integrity, residual volume, and door opening after the test can be addressed by looking at the deformed shapes of the vehicle during the crash event. During the early stages of the impact, there should be a little or no deformation in the interior. This sequence of events (Fig ) is necessary up to the time that the tires make contact with the barrier face and transfer load to the suspension and the rear of the rocker panel. For the rear crash a half structure model was used. The rear crash deformed shapes are shown in Fig To analyze the rear passenger compartment integrity, Figure shows that maximum dynamic intrusion in this area. The diagram (Fig ) shows the energy absorption, and the cross sections of the main hood load paths are shown in Figure Due to the results, the rear rail and the rocker were the most important hood paths of the rear structure. The Rear Crash Acceleration vs. Time (Fig ) shows an average acceleration of the rocker RHS and the tunnel. Figure shows the total car deformation, at approximately 85 ms, the maximum dynamic deformation was reached. Chapter 6 - Page 25

120 Figure Rear Crash Analysis Setup Chapter 6 - Page 26

121 t = 0 ms t = 100 ms t = 0 ms t = 100 ms Figure Rear Crash Deformed Shapes Chapter 6 - Page 27

122 X 120 X 73 X 5 X 4 X 53 X 38 X 33 X 66 X 2 Figure Rear Crash Maximum Dynamic Room Intrusion (mm) Rear Rail 20.2 Crash Box Rear 1.4 Panel Rear Floor 6.3 Bumper Rear Energy (kj) Figure Rear Crash Internal Energy Absorption (kj) Chapter 6 - Page 28

123 Rocker 50 Rear Rail 80 Rail Side Roof 15 Spare Wheel Force (kn) Figure Rear Crash Typical Cross Section Forces (kn) Average Car Acceleration vs. Time ax [g] time [ms] Figure Rear Crash Acceleration vs. Time Chapter 6 - Page 29

124 Car Deformation vs. Time sx [mm] time [ms] Figure Rear Crash Deformation vs. Time Chapter 6 - Page 30

125 The following table (Fig ) explains the rear crash events after impact: Time (ms) Rear Crash 4.00 Initial folding of longitudinals rear Spare tire contacts barrier First buckling of crossmember rear suspension Spare tire hits crossmember rear suspension Buckling of the crossmember rear suspension Buckling of the rear end rocker at the connection to longitudinal rear Collapse of crossmember rear suspension Buckling of the front end longitudinal rear Maximum dynamic deformation reached Figure Rear Crash Events This analysis shows that the structural integrity of the fuel tank and fuel filler was maintained during the event, so no fuel leakage is expected. The spare tire tub rides up during impact, avoiding contact with the tank. Rear passenger compartment intrusion was restricted to the rear most portion of the passenger compartment, largely in the area behind rear seat. This result is due to good progressive crush exhibited by the rear rail. Chapter 6 - Page 31

126 Side Impact Analysis The conditions for the side impact analysis are based on a European Side Moving Barrier Test. The European test specifically addresses injury criterion based on displacement data gathered from EUROSID side impact crash dummies. Automotive companies also include post-crash structural integrity and passenger compartment as additional requirements for this test. The actual European side moving barrier uses a segmented deformable face which complies with a required set of different load versus displacement characteristics and geometric shape and size requirements. The barrier used in the analysis (Fig ) conformed to the geometric requirements (i.e., ground clearance, height, width, bumper depth). The European specification requires the impacting barrier to have a mass of 950 kg, making contact at ninety degrees relative to the vehicle longitudinal axis. The center line of the barrier is aligned longitudinally with the front passenger R-point. The R-point is a car specific point which is defined by the seat/ passenger location. The velocity of the side moving barrier at time of impact is designated to be 50 km/h. Because the scope of analysis did not include side impact dummies, injury assessment could not be made. Injury performance is greatly affected by interior trim panel and foam absorber design as well as by structural crush. Evaluation of passenger compartment intrusion can be made by looking at door and B-pillar displacements and intrusion velocities. Structural integrity can be assessed by looking at the overall shape of the deformation, including any gross buckling of the B-pillar, rotation of the rocker rails, crush of the front body hinge pillar, folding of the door beams and door belts, and cross-car underbody parts such as the seat attachment members and the rear suspension cross member. Chapter 6 - Page 32

127 Figure Side Impact Crash Analysis Setup The side impact undeformed and deformed shapes are shown in Fig and , with the deformed shapes shown after 80 ms of impact. During the early stage of the impact, the outer door structure crushes, the B-pillar is stable. As the impact progresses the rocker starts to buckle and causes also a bulging of the floor section. At about 30 ms, the still stable structure of the B-pillar is moved by the barrier inside the car and therefore the roof starts to bulge. After 40 ms the B-pillar develops an inward buckling. After about 64 ms the maximum dynamic deformation is reached. For the injury performance, the intrusion velocities of the structural parts, which could come in contact with the passengers, are important. Figures and show the intrusion velocities of typical points at the inner front door panel (No. 238) and the B-pillar inner (No. 235) (Fig ). The following Figures and show the deformed shape of the side structure: Chapter 6 - Page 33

128 t = 0 ms t = 80 ms Figure Side Impact Crash Deformed Shapes Chapter 6 - Page 34

129 t = 0 ms t = 80 ms Figure Side Impact Crash Deformed Shapes of Side Structure No. 238 No. 238 No. 353 No. 353 Measured points for velocity Lower B-pillar enlarged Figure Side Impact Time History Node Chapter 6 - Page 35

130 Velocity vs. Intrusion Door Inner Panel No Y - Velocity [m/s] Y - Intrusion [mm] Figure Side Impact Velocity vs. Intrusion at Node 353 Velocity vs. Intrusion B-Pillar No Y - Velocity [m/s] Y - Intrusion [mm] Figure Side Impact Velocity vs. Intrusion at Node 238 Chapter 6 - Page 36

131 The following table (Fig ) shows the side impact crash events: Time (ms) Side Impact Buckling of the rocker in front of B-pillar Buckling of the floor Buckling of the roof Buckling of the roof frame at the B-pillar Buckling of the member kick up, still stable Buckling of the brace tunnel Maximum dynamic deformation reached Figure Side Impact Crash Events The body side ring and doors maintained their integrity with only 248 mm of intrusion. The velocity of the intruding structure was tracked to determine the degree of injury an occupant may sustain. The maximum velocity was only 8 meters per second. The event is considered complete when the deformable barrier and vehicle reach the same velocity, in this case at 64 msec. Chapter 6 - Page 37

132 Roof Crush (FMVSS 216) The conditions for the roof crush analysis are based on United States, FMVSS 216. This requirement is designed to protect the occupants in event of a rollover accident. The surface and angle of impact are chosen to represent the entire vehicle impacting the front corner of the roof. The federal standard requires roof deformation to be limited to 127 mm (5 inches) of crush, and roof structure to support 1.5 times the vehicle curb mass or 5,000 lbs (22249 N), whichever is less. For test purposes and repeatability, the complete body in white is assembled and clamped at the lower edge of rocker and the roof crush test is done in a quasi-static force versus displacement arrangement. In the computer analysis, the software program, LS-DYNA, requires that the roof crush be done in a dynamic, moving barrier description as compared to the quasi-static test. Figure shows the undeformed shape of the FE-Model used for the roof crush simulation. The shape of the structure after the limit of 127 mm deformation is shown in Figure The force versus displacement curve is shown in Fig The peak force of N is reached after a deformation of 72 mm of roof crush. Based on the curb mass of 1350 kg, the crush force of N is required for the federal standards FMVSS 216. The analysis was continued to 127 mm (5 inches) of deflection in order to determine the ability of the roof to sustain the peak load past 72 mm of crush. The analysis shows that the roof meets the peak load requirements and is steady and predictable. Chapter 6 - Page 38

133 Figure Roof Crush Undeformed Shape Figure Roof Crush Deformed Shape Chapter 6 - Page 39

134 Force vs. Deformation Force [N] Deformation [mm] Figure Roof Crush Deformation vs. Force Analysis showed that kn was reached within 30 mm of crush. The structure resisted the applied load all the way up its peak of kn and continued to maintain it quite well even after peak, when it dropped to about 28 kn at 127 mm. The load was well distributed through the A, B and C-pillars and down into the rear rail CAE Analysis Summary For the AMS Offset crash test the overall deformation and intrusion are the critical figures. For the NCAP crash test, the critical figure is the vehicle crash pulse. The target for the offset crash was to achieve low footwell intrusion. It is important to achieve a good balance between these two targets. The results of the crash analysis show that for the ULSAB a good compromise has been found to fulfill the AMS as well as the NCAP frontal crash, considering the dependencies between these two crash types. To achieve the low footwell intrusion for the AMS crash a rigid front structure is needed. A rigid front structure, however, means higher acceleration in the NCAP Chapter 6 - Page 40

135 test and results in higher HIC (Head Injury Criteria) values for the passengers, with a maximum footwell intrusion of 149 mm for the AMS Offset crash and a maximum acceleration of 30.4 g for the NCAP crash, the ULSAB structure shows a good balance in these criteria. The results also document the high safety standards of ULSAB, especially if one considers that the NCAP crash analysis was run at 5 miles above the required speed of 30 mph and 36% more energy had to be absorbed. The rear crash test requirements are addressing the fuel system integrity and low deformation in the rear seat area. The analysis shows no collapse of the surrounding structure of the fuel tank, contact with the fuel tank itself or the fuel filler routing. Considering the fact that there was no rear seat structure the analysis also shows a low deformation of the rear floor. For the rear crash analysis in the ULSAB program, the requirement was raised from 30 mph to 35 mph velocity of the rear moving barrier, resulting in an increase of 36% of its kinetic energy. In the side impact crash test, good performance means acceptable intrusion of the side structure at low intrusion velocity. For both criteria the ULSAB achieved satisfactory results. The analysis shows a maximum intrusion of 250 mm and an intrusion velocity of 8 m/s at the inner door panel and the B-pillar. It is assumed that in a fully equipped car the intrusion will be even lower. For the roof crush test the Federal standard requires the roof deformation to be limited to 127 mm of crush and the structure to support 1.5 times the curb mass or 5000 pounds, whichever is less. The force requirement of N was already met at 27 mm of crush. The continued analysis showed that the structure is steady and peak load of 36 kn was met after 72 mm of crush. This result confirms the role the side roof rail plays as important part of the ULSAB structure. The ULSAB crash analysis has shown that reducing the body structure mass using high strength steel, in various grades and in applications such as tailor welded blanks combined with the applied joining technologies in the assembly, such as laser welding, does not sacrifice safety. The goal was to maintain the high standards of state-of-the-art crash requirements, without compromising the ULSAB program goal to significantly reduce the body structure mass. The crash analysis of the ULSAB supports that this goal is reached. Chapter 6 - Page 41

136 7. Material & Processes Engineering Services, Inc.

137 7. Material and Processes 7.1. Material Selection Material Selection Process Based on ULSAB Phase 1 results, the body structure was redesigned in Phase 2 as described in earlier chapters of this report. With respect to the new influences, such as crash requirements and styling, new calculations had to be made. The calculations concerning static behavior gave us a first indication of the sheet metal thickness needed. This is because performance is mainly related to sheet metal thickness and the design itself, and not to the strength of the material, because the E-modulus is very similar for all steel types. After the initial material selection, the first loop of crash calculations was performed. As a result, the material grades and/ or the sheet metal thicknesses had to be adjusted. Several iterations of the Material Selection Process (Figure ) lead us to the optimal strength/thickness level for each part. This procedure included a manufacturing feasibility check with our selected part suppliers. For the most critical parts, a forming simulation was performed simultaneously by the steel suppliers. The results of these simultaneous engineering processes have been important factors in successfully meeting the challenges of developing manufacturable parts. Different criteria during the material selection process such as formability, weldability, spring-back behavior, and static and dynamic properties were always taken into consideration. Always having Production Intent in mind, the focus was on production-ready materials, not on materials that are available only in laboratory scale. General material specifications and the definition of the different material grades are described in section 7.2 of this chapter. Chapter 7 - Page 1

138 Material Selection Process Start No Phase 1 Package / Concept Design Phase 2 Package Refinement Create Styling Concept Modify Package/ Styling / Design Modify Phase 1 Shell Model Meets Static Targets No Modify Design Material / Thickness Adjustement Steel Supplier and Part Supplier Input Yes Meets Static/Crash Targets Create / Modify Phase 2 Crash Model Yes Meets Static Targets Create / Modify Phase 2 Shell Model Material / Thickness Selection, Design Modification Yes No No No Parts Feasible Yes Build of First Test Unit Meets Static / Crash Targets Yes Build of Final Demonstration Hardware Figure Definition of Strength Levels In order to use the minimum variety of materials, every master item was defined by thickness and strength. The same master item could be used for different parts, as long as thickness and strength requirements were met, and the part suppliers and forming experts had no concerns. The definition of strength levels as used in ULSAB Phase 2 is shown next in the ULSAB High Strength Steel Definition. Chapter 7 - Page 2

139 ULSAB High Strength Steel Definition The ULSAB program designates steel grades by specified minimum yield strength in the part. The following steel grades are utilized in the ULSAB design: Minimum Yield Strength Category 140 MPa Mild Steel 210 MPa High Strength Steel 280 MPa High Strength Steel 350 MPa High Strength Steel 420 MPa High Strength Steel Greater than 550 MPa Ultra High Strength Steel This definition was chosen in order to standardize the steel grade definitions for the ULSAB Consortium member companies since many countries are involved and the standards are not the same around the world. This has to be seen together with the goal that the ULSAB body structure could be built in every region of the world where steel is available. This is also the reason that the suppliers of the material for the DHs are kept anonymous within the ULSAB program. The most suitable material for each part application was chosen with the assistance of experts from the steel suppliers. This process was especially important for the ultra high strength steel because of its more critical forming behavior. Different materials such as dual phase (DP) steels are included in this group of ultra high strength material parts. There are several ways to achieve the 280 MPa yield strength level according to the above definition. This could be done by using microalloyed high strength steel, bake hardening or even dual phase steel. However it is achieved, the minimum yield strength for the finished part has to be 280 MPa in each area of the part. Other material qualities and material types could achieve the same or similar results; therefore, several factors affected material selection including material performance and availability. Chapter 7 - Page 3

140 Supplier Selection Once the master items were defined, the material supplier selection was made. This was done in material group meetings attended by all steel supplier experts and the design and manufacturing team of PES. For every part of the ULSAB, a minimum of two material sources were selected. The fact that different materials with the same yield strength level were available for each part (not only from different suppliers, but also in many cases different material types, such as microalloyed or dual phase) shows that most of the ULSAB parts could be made in multiple ways. No specially treated or designed material was necessary. Most of the material was taken from normal serial production at the steel mills. In order to practice simultaneous engineering most efficiently, the material suppliers were selected by their close proximity to the part supplier s location (press shop). If the material failed during the first try-outs it was easier to react with corrective steps such as circle grid analysis, material tests, or forming simulations. Similar criteria were used in selecting the welding sources for the tailor welded blanks. In most cases two different companies could have provided the same welded sheet, each with slightly different material qualities. This again underscores that the ULSAB can be built with widely available material and part manufacturing technology. Chapter 7 - Page 4

141 7.2. Material Specifications General Specifications General specifications for the material used on the ULSAB only concerned thickness tolerances, coating requirements and coating tolerances. The specifications are as follows: Actual thickness of blanks must measure mm/-0.02 mm of the specified thickness Coating may be electro-galvanized (Zn only) or hot dip (Zn or ZnFe) Coating thickness must be 65 gram/m² maximum (0.009 mm) per side with coating on both sides Every delivered material had to be tested at the supplying source before it was shipped to the part manufacturer. A test report accompanied the material until the parts are finished. This is the basis for the Advanced Quality Planning (AQP) report that was performed by the ULSAB Consortium. The test results are also considered for welding parameter evaluation at the prototype shop Material Classes Mild Steel Definition Mild steel, which is described in Sec 7.1 Material Selection, is material with a yield strength level of 140 MPa. Mild steel can also be defined in terms of Draw Quality, Deep Draw Quality or Extra Deep Draw Quality. The material has no fixed minimum yield strength but does have a minimum elongation. Mild steels are the most common steels used in auto making today. This is because mild steel has forming and cost advantages compared to high strength steel. On the other hand, the ULSAB clearly shows that the amount of high strength and ultra high strength steel can be used up to more than 90% or more without any cost penalty. Chapter 7 - Page 5

142 High Strength Steel Definition The steel industry has developed various high strength steel qualities. In the ULSAB Phase 2 program the strength levels of 210, 280, 350 and 420 MPa were defined as high strength steel. The values are related to the strength of the finished parts as assumed in the FEA model. This includes additional strengthening as a result of the bake-hardening process also. High strength steels were used where the design required certain crash and strength characteristics. Within the range of this material group, different strengthening mechanisms can contribute to the final result. The DHs used microalloyed steels, phosphor-alloyed steels, bake-hardening steels, isotropic steels, high-strength IF - steels and dual-phase steels, all in the range of the abovementioned yield strength. This engineering report does not include a detailed description of alloying or other metallurgical processes that are used to produce those steel types Ultra High Strength Steel Definition Ultra high strength steels are defined as steels with a yield strength of more than 550 MPa on the finished part. Parts made from these steels can provide additional strength for front and side impact. In the ULSAB structure, all crossmembers of the floor structure were designed in ultra high and high strength steel. Today, there are different ways to achieve needed strength levels. This could be done for automotive sheet panels with dual phase (DP) steels, or with boron-alloyed types, which have to be hot formed. Within the ULSAB Phase 2, parts were made from DP steels. DP steels were feasible even on parts with a complex shape like the cross member dash. As of today, those types were also available in an appropriate thickness range, which is interesting for automotive applications, e.g. a thickness between 0.7 and 1.5 mm. Chapter 7 - Page 6

143 Sandwich Material Definition The use of sandwich material has contributed to considerable mass savings on the ULSAB. The sandwich material is made with a thermoplastic (polypropylene) core, which has a thickness of about 0.65 mm. This core is sandwiched between two thin outer steel sheets with a thickness of about 0.14 mm each. The polypropylene core of this sandwich material acts as a spacer between the two outer sheets, keeping the outer surfaces away from the neutral axis when a bending load is applied (see fig ). The mentioned material (total thickness about 0.96 mm when coated) has a very similar behavior compared to a solid sheet of steel with a thickness of about 0.7 mm. Steel Sheet 0.14 mm Polypropylene Core 0.65 mm Steel Sheet 0.14 mm Figure Sandwich Material This sandwich material shares many of the same processing attributes with steel sheets, like deep drawing, shear cutting, bonding, etc. But, unfortunately, it cannot be welded. Even mechanical joining like riveting, clinching or screwing, can be a problem when the material has to go through the paint-baking oven. The core material is softened by the heat and flows away from the area where a pretension from a screw is applied. This may lead to a loss in joining strength. Therefore, applications used in the ULSAB Phase 2 design were with parts made from sandwich material that did not go through the oven. The spare tire tub is designed as a prepainted module, preassembled with spare tire and tools. This module will be dropped into place and bonded to the structure during the final assembly of the vehicle. No additional heat has to be applied. Another application of sandwich material is the dash panel insert, which was bolted and bonded into the panel dash during final vehicle assembly. Chapter 7 - Page 7

144 Because there was no application similar to the spare tire tub in the past, an extensive forming simulation was performed on this part. Once the design was adjusted using the results of the simulation, there were no major concerns about the feasibility of the spare tire tub. After a small refinement of the best drawable radius, the parts were determined to be manufacturable with no problems. Furthermore, a physical test with the spare tire tub was performed to check the fatigue behavior of this material for the application. Parts from the described sandwich material were made and compared to parts made from solid steel sheets of 0.7 mm thickness. A picture of the test installation is shown below in Fig F Figure Test Installation Chapter 7 - Page 8

145 The load signal that was applied was taken from Porsche s proving ground and adjusted to the situation of the ULSAB. The test concluded there are no restrictions for the use of the sandwich material for the proposed application when it is compared to a conventional design using a 0.7 mm solid steel sheet. The parts that were designed for the ULSAB could be made up to 50% lighter than those made of solid steel under similar dimensional and functional conditions. But, higher costs for the sandwich material have to be taken into consideration as compared to normal coated steel sheets Material Documentation As mentioned earlier, every Master Item (material defined by thickness and strength) was accompanied by a test report, which includes all important strength properties, r- and n- values and a coating description. Those tests were performed by the supplying steel mills. All the supplied materials are documented at PES with their corresponding values, such as blank size, properties, coatings, material type etc. The Master List was also the base for the documentation of the welding parameters and the DH build itself. When the parts were manufactured, the above-mentioned documentation was completed with additional information concerning press conditions for parts made at different locations. For those parts where a forming simulation and/or a circle grid analysis were performed, the documentation was extended with the results from these additional steps. These results are included in the earlier mentioned AQP report. To ensure proper and comparable documentation, material samples from every part, that goes into the DH were collected by PES and sent to a central testing source. At this neutral location, every collected material was tested in the same way and documented again. Chapter 7 - Page 9

146 7.3. Tailor Welded Blanks Introduction Tailored blanking for vehicle body structures is a well known process with the first applications being done for mass production which started in Below listed are the main reasons for PES s decision to use tailor welded blanks in a relatively large number compared to vehicles already on the market: Mass reduction due to the possibility of placing optimum steel thicknesses and grades where needed Elimination of reinforcements with appropriate material gage selection Simplified logistics due to the reduction of parts Investment cost reduction of dies, presses etc. due to fewer production steps Better corrosion protection by the elimination of overlapped joints Improved structural rigidity due to the smoother energy flow within the tailor welded blank parts Better fatigue and crash behavior compared to a conventional overlapped spot welded design solution Selection of Welding Process Laser welding and mash seam welding are the most common processes for the manufacturing of tailor welded blanks today. Induction and electron beam welding have a minor importance and they are still under development. All these processes have their advantages and disadvantages, related to the process and the machine itself. Induction welding is a butt welding process. The necessary compressing of the two sheets creates a bulge with the consequence of an increase in thickness in the joined area. Those blanks could not be used in visible areas without an additional surface finishing process. A high accuracy during the movement of the sheets is important. The heating of the weld seam by induction / magnetic current over the total length leads to a larger heat affected zone when compared to laser welded blanks. Chapter 7 - Page 10

147 The non-vacuum electron beam welding process is similar to laser welding in the result of the weld seam geometry. This is due to the fact that it is a non-contact process as well. The beam is a mass beam and the kinetic energy of this beam is used for heating the material. The beam can be focused by a magnetic spool and the diameter can be adjusted easily. The advantage of this process compared to laser is the increased efficiency of about 90% compared to 10% when using laser. But a disadvantage is that the electron beam creates x - rays. This influences the machine design dramatically regarding total investment and material handling. Therefore this process is not used extensively up to now. Mash seam welding needs a narrow overlapping of the sheets which have to be welded. The material in this area becomes doughy, not really fluid. During the welding process the current flows from one electrode to the other one and by resistance heating the sheet material becomes doughy. The electrode force then mashes the weld area and the sheets are joined together in this way. This light overlap and the joining process by force loaded electrodes results in a weld zone between 2.5 and 3.0 mm. The coating maybe is affected in this zone negatively. Furthermore, experience has shown that the surface of the weld zone, where little caves and pinchers occur due to the mash welding process, may not achieve the required corrosion resistance. The laser welding process is used more and more widely. It is a non-contact welding process, and the heat is brought into the material by a coherent light with high energy density. In this way a very narrow weld zone can be achieved. There is almost no influence on the corrosion resistance when coated material is used. The main critical point on this process is without any doubt the need for very precisely prepared edges of the sheet. But this problem could be overcome by today s available precise cutting technologies or advanced fixing and clamping devices. One of the biggest advantages is the possibility of a non-linear weld line layout. Different combinations of laser sources and clamping devices are on the market today. In many cases the sheets are moved relative to the fixed laser beam. This may lead to a reduction of the cycle time of the whole process. Chapter 7 - Page 11

148 Together with the fact that most of the newest installations for welding blanks are laser equipped devices, and the positive experience of PES, has lead to the decision to use laser welded tailored blanks on the ULSAB body structure exclusively. The blanks were produced at different locations using different equipment from the whole range of possible installations. The weld lines were controlled during the joining process to maintain the following features: width of the remaining gap mismatching of blank edges blank position seam geography (concavity, convexity) lack of penetration All of these lead to the high quality of today s tailor welded blanks Weld Line Layout The weld line layout was mainly driven by the crash calculation results. Forming feasibility requirements also influenced it. On some of the most critical parts, e.g. the body side outer panel, a forming simulation was performed. Necessary changes from this simultaneous engineering process were incorporated in the weld line layout. The following parts on the ULSAB body structure were designed as tailor welded blanks: Front Rail Outer Front Rail Inner Panel Rocker Inner Rear Rail Inner Rear Rail Outer Panel Body Side Outer Panel Wheelhouse Outer Panel Skirt Chapter 7 - Page 12

149 The weld line layout is shown in the following pages for each part. ULSAB Rail Front Outer 1.5 (350 MPa) 1.6 (350 MPa) 2.0 (350 MPa) ULSAB Rail Front Inner 1.5 (350 MPa) 1.6 (350 MPa) 1.8 (350 MPa) ULSAB Panel Rocker Inner 1.7 (350 MPa) 1.3 (350 MPa) Chapter 7 - Page 13

150 ULSAB Rail Rear Inner 1.6 (350 MPa) 1.3 (350 MPa) 1.0 (350 MPa) ULSAB Rail Rear Outer 1.6 (350 MPa) 1.3 (350 MPa) 1.0 (350 MPa) ULSAB Panel Body Side Outer 1.3 (280 MPa) 0.7 (210 MPa) 1.5 (350 MPa) 1.7 (350 MPa) 0.9 (280 MPa) Chapter 7 - Page 14

151 ULSAB Panel Wheelhouse Outer 0.8 (210 MPa) 0.65 (140 MPa) ULSAB Panel Skirt 2.0 (140 MPa) 1.6 (140 MPa) Chapter 7 - Page 15

152 Production Blank Layout Figure For the Economic Analysis cost calculation purposes, the production blank layout for the tailor welded blank parts was developed Hydroforming General Process Description Today, tubular hydroforming is a well-established process in automotive manufacturing. When ULSAB Phase 1 began several years ago and hydroforming was chosen as the manufacturing process for the side roof rail, the technology was being used mainly for exhaust pipes and some front cradles. These had a much smaller diameter-to-thickness ratio compared to the ULSAB side roof rail. But with the focus on mass savings, it was assumed that hydroforming could reduce the number of parts while helping to optimize available package space. Chapter 7 - Page 16

153 The hyroforming process is described very simply as: put a tube between a lower and an upper die, close the die, fill the tube with water and increase the internal pressure in order to force the tube to expand into the shape of the die. However, several things must be taken into consideration within this process technology. This method will work only for straight tubes. In all other cases the tube has to be prebent or preformed depending on the final shape. The various steps necessary for the manufacturing of the ULSAB side roof rail will be explained in the next section Benefit for the Project As explained in the Phase 1 report, the use of hydroformed parts instead of conventionally formed and spot-welded structures have certain apparent advantages. Because of the absence of flanges, available space could be utilized with higher efficiency (bigger cross sections were achievable). The homogeneous hydroformed parts also provide an improved load flow in comparison to other structural members made of several parts joined by spot welding. The side roof rail represents a significant structural member in the ULSAB structure and provides an optimal load distribution from the A-pillar along the roof into the B and C-pillar. This is true for the static as well as for the dynamic behavior of the body structure. Also the side impact and the rear crash support is affected positively. The interior of the vehicle is well protected by the roll bar design of these two structural members integrated into the body structure. The hydroformed parts described in ULSAB Phase 1 already have led to similar applications in vehicles that are on the road today. There is a high potential for further steel applications on comparable parts that are loaded with high forces. Other opportunities for hydroformed steel structures will be in the area of protection systems for convertibles. Chapter 7 - Page 17

154 Forming Simulation (Review) First, a feasibility check was made using the predicted bending line along with analyzing the material distribution over the circumference in different cross sections. Next, the design of the side roof rail was analyzed and optimized for feasibility by conducting a forming simulation. Simultaneous engineering was used by the team consisting of PES and the part manufacturer; a similar approach was used for the development of the conventional stamped parts. Conducting a forming simulation for parts like the side roof rail is much more complex than for stamped parts. This is because material properties that are affected by a combination of processes such as prebending, preforming and hydroforming are very difficult to calculate. The first forming simulation has shown that wrinkles will occur during a very early stage of the forming process in the area where the tube was first prebent. The next step is to preform in a different direction to make it fit into the hydroforming tool. A picture of this area taken from the forming simulation program is shown in Figure Figure Forming Simulation As a result of this analysis the design of the side roof rail was modified so that some bending radii were softened. Also some other areas were slightly changed in order to prevent excessive material thinning or cracking during the forming process. The forming simulation also led to the decision of using a separate preforming tool (described in Sec ). Chapter 7 - Page 18

155 Tube Manufacturing Certain material qualities have to be defined. Standard tubes, beside the fact that the required diameters with the needed thin wall were not available commercially, have no high demand concerning transversal elongation. But this is one of the main factors during the hydroforming process when the tubes are expanded. Even if the difference in diameter on different cross sections of the tube is relatively low, certain areas of the ULSAB hydroformed side roof rail required a high degree of elongation. During the design process, differentiation must be made between local elongation (between two points of the circumference) and the overall elongation (total difference in circumference in a cross section). These two factors must also be taken into consideration for the longitudinal shape of the part. Transitions between shape changes of the cross sections should be as smooth as possible and high elongation is needed. The above mentioned facts led to the decision to manufacture tubes for the ULSAB side roof rail from material different to what is used for conventional tubes. Tubes were made, therefore, from high strength steel sheets to meet yield strength requirements and to have uniform elongation in both directions. High work hardening, which should be achievable by this material, is an important factor as well. Tubes can be made in several different ways. One way is to manufacture them with a continuous roll forming and high frequency welding. This has to be done with extremely high accuracy of the weld geometry especially on such thin walled large diameter tubes. Because the burr (which is unavoidable in this process) has to be removed in an additional planing operation (scarfing), not all of the welds are able to meet the tube specifications. Another approach is to use non-contact laser welding for the joining process. This eliminates the burr and therefore no additional operations are needed; it also creates a much-narrowed heat-affected and dezinced zone. For these reasons the tubes for the ULSAB structure were laser welded. Chapter 7 - Page 19

156 For the prebending process, which requires a tube with small tolerances and a finished part with high strength, the following tube specifications were created: Quality Feature: Precision steel tube according to the following tolerances Material: Zinc coated on both sides details see below Yield Strength: > 260 N/mm² (> 280 N/mm² on finished parts) Total Elongation: > 32% (longitudinal and transverse) Uniform Elongation: > 20% r - Value: > 1.80 Dimensions and Tolerances Outside Diameter: 96 mm +0.1 / 0 Wall Thickness: 1.0 mm; tolerances according to ULSAB specification Total Tube Length: 2700 mm +/- 1 Cutting of Tube Ends: Free of Burr No ovalization or cave-in No chamfers Rectangular to longitudinal axis +/- 0.5 Appearance of Tubes Surface: Free of mechanical damage, splatters, etc. No collapsed areas (no indents, bulges, etc.) Free of impurities (swarf, weld chips etc.) Welding Requirements Welding Process: Weld Seam Area: Laser- or high-frequency welding Outside of tube: Undercut 0.0 mm, no expansion Inside of Tube: Undercut < 0.2 mm, no expansion No mismatch of edges Free of any porosity Strength similar to base material Chapter 7 - Page 20

157 Process Steps for Rail Side Roof Because the side roof rail has several 2-dimensional bendings with different radii over its length and two 3-dimensional curves in the rear portion, the straight tube has to be prebent. At the beginning of the design phase, bending tubes with such a high diameter (96 mm) -to-wall-thickness (1.0 mm) ratio resulted in very poor bend quality. At first, the tubes were bent by using a conventional mandrel-bending machine modified in such a way that the mandrel was replaced by internal fluid pressure. This inside pressure is working as a substitute for a mandrel. The purpose of this was to maintain stricter tolerances which are directly related to the accuracy of the bending tools, the diameter of the mandrel used, and the tube diameter and wall thickness. In this way, the tubes could be bent into the needed shape without any wrinkles. However, because the pressure was applied inside the whole tube, the tube diameter increased to a point that the tube would not fit into the next die. Therefore, Porsche went back to using the solid mandrel. By holding to stricter tolerances and taking certain other steps, wrinkle-free tubes could be formed. With this process, the clamping force needed to avoid wrinkles or damage to the tube has to be kept within a tight tolerance. Once the tube is prebent, preforming is the next step. This is done in a three-piece tool under low internal pressure to avoid collapsing. The tube is then flattened and bent again in order to fit into the final hydroforming die. The basic layout of the preforming tool and the tool itself is shown in Figure , 2 & 3. Outer tool part Section A - A Tube Moving direction of outer tool part Inner tool part Upper tool part not shown Figure Preforming Tool Concept Chapter 7 - Page 21

158 Tube filled with water under low pressure Outer tool part moved to inner pert Upper tool part closed Pressure released and die opened Figure Sec. A-A of Preforming Tool Concept Upper tool part Inner tool part Outer tool part Figure Preforming Tool Chapter 7 - Page 22

159 The final step is the hydroforming process itself. During the down movement of the upper half of the die there is another area preformed again (under low internal pressure) on the tube. This must be done because the hydroforming process is very sensitive to die locking. Once the die is finally closed, the internal pressure is increased and the side roof rail tube is calibrated into its final shape. The pressure has to be raised to 900 bar for the side roof rail in order to set the final shape of the part. This required a closing force of about 3200 tons. This internal calibration pressure was higher than predicted by calculation and forming simulation. A picture of the hydroforming tool is shown in Fig Figure Hydroforming Tool Chapter 7 - Page 23

160 Results Hydroforming has never been used previously to form a high strength steel tube with such a high diameter-to-wall-thickness ratio. Nevertheless the goal to manufacture the side roof rails was achieved. There is still room for improvement, but the main problems related to the bending and preforming operations were resolved. Hydroforming will be only a calibration operation if all-important steps before this were optimized. With the experience gained from the ULSAB Phase 2, producing similar hydroformed applications should be easier in the future. Chapter 7 - Page 24

161 7.5. Hydromechanical Sheet Forming General Process Description Hoods, roofs and door panels (large body outer panels) produced by conventional forming methods often lack sufficient stiffness against buckling in the center area of the part. Due to the low degree of deformation in the center, there is only a little work hardening effect that could be achieved. Therefore, material thickness has to be increased to meet the dent resistance requirements on those parts. This of course leads to heavier parts and creates extra costs. The active hydromechanical sheet metal forming process is a forming technology that uses an active fluid medium. The die consists of three main components: a drawing ring, which is designed as a water box, the blankholder (binder) and the drawing punch itself. At the beginning, the die is open and the blank is loaded on the ring (see figure ). Slide Cylinder Blankholder Cylinder Slide Blankholder Moving Balster Figure Active Hydro-Mec Process Step: Loading / Unloading Chapter 7 - Page 25

162 In the second stage, the die is closed and the blankholder clamps the blank. The die punch has a defined, part specific regress against the clamped blank, as in figure A pressure intensifier is used to introduce the water emulsion into the water box, where a pre-set pressure is generated. The blank is inflated in a controlled manner and stretched over the complete area until it is pressed against the punch. This is the reason why the process is called active hydromechanical sheet metal forming. Forming with fluids (or flexible rubber layers) is well known already, but previously there was no forming in the opposite direction within those processes. The plastic elongation produces a work-hardening effect, especially in the center of the part. This effect significantly improves the dent resistance of the formed part. Figure Active Hydro-Mec Process Step: Pre-forming Chapter 7 - Page 26

163 Once the first plastic elongation process is done, the draw punch is moved downward, as in figure At the same time, the emulsion is evacuated from the water box and the pressure of the fluid is lowered in a controlled process. After completion of the drawing operation, pressure is increased once more in order to calibrate the part into the final shape. The later visible surface of the part (outer side) is turned towards the active fluid medium. There is no contact to metal on this surface and an excellent surface quality of the part was achieved. Source: SMG Engineering Germany Figure Active Hydro-Mec Process Step: Forming Completed Chapter 7 - Page 27

164 A picture of the formed roof panel is shown below in figure Figure Roof Panel Benefit for the Project The active hydromechanical sheet metal forming process is characterized by improved component quality and potential mass and cost reduction. The essential features of this new technology are: higher dent resistance achieved by an increased work-hardening effect during the first counter forming operation, and superior visible surface quality achieved by using water instead of a metal die for the final forming operation. This leads to a reduced component mass due to increased stability. Sheet thickness could be reduced to 0.7 mm and reinforcement elements could be saved, while all other requirements were still fulfilled. In addition, the cost of dies can be reduced by about 40% because only one polished half of the die is required. In addition, the average lifetime of the dies will last longer, under mass production conditions, than usual because there is little wearing off when forming with a fluid medium. In order to get the most benefit out of this process a forming simulation should be performed. This simulation may help to predict the maximal prestretching amount achievable without damaging the sheet. The absence of friction between the blank Chapter 7 - Page 28

165 and the conventionally used second half of the die makes the result of the simulation very reliable. Furthermore, the process parameters, (e.g., preforming pressure, etc.) could be easily adjusted Process Limitations Depending on the grade of prestretching, which is related to the preforming pressure, the size of the forming press (locking force) has to be chosen. This is also influenced by the overall projected area of the part (e.g., for the ULSAB roof panel, a press with a locking force of 4,000 was chosen.) A double (or triple) action hydraulic press must be used to make the process reliable. This press can be used for conventional forming, and with the use of some additional equipment, for the tubular hydroforming process. The filling time for the fluid medium pressure bed has to be taken into account as well. This leads to a calculated cycle time for the ULSAB roof panel of about seconds. Depending on the design of the part, this has to be compared to a two-step conventional forming operation. Due to potential die locking, it appears that an undercut on the hydroformed parts is not feasible in this process without using a separate tool. This is also relevant for the cutting of flanges. This has to be done separately using laser or conventional trimming operations. Chapter 7 - Page 29

166 Results Roof panels for the ULSAB could be manufactured by using the active hydromechanical sheet metal forming process. Different material qualities, like isotropic, IF and bake-hardening types, were formed successfully. Due to the workhardening effect, which was applied through the above-described process, the sheet thickness of the roof panel could be lowered to 0.7 mm, while the dent resistance requirements were still met. In order to limit the needed locking force of the press, the flange radii should be designed not too small. The radii are directly related to the needed pressure during the final forming operation, and if too small lead to an uneconomic high-locking force/press size. The surface quality on the visible side of the ULSAB roof panel, which was not in contact with any metal tool, was very high compared to conventional formed (prototype) parts. Chapter 7 - Page 30

167 8. Parts Manufacturing Engineering Services, Inc.

168 8. Parts Manufacturing 8.1. Supplier Selection The main criterion for supplier selection was quality. Although the process used soft tools and lasers, the contract required production representative parts. Therefore, it was decided to identify companies that specialize in one or more of the following system groups: Front End Structure Floor Panels and Body Side Inner Body Side Outer Rear Structure Roof and Roof Side Rails Extensive discussions took place with approximately 30 suppliers on a worldwide basis to identify the sources for the ULSAB program. The criteria used to rationalize the final selections were: Supplier must have major OEM quality rating or ISO 9000 Must be a system supplier to a major OEM Must be prepared to enter simultaneous engineering prior to contract release CAD/CAM systems compatible with CATIA Program management system established Experience in match metal checks Cost competitive Chapter 8 - Page 1

169 Based on the foregoing, the following companies were selected: Front End Structure Stickel GMBH, leading supplier to Porsche AG Floor Panels and Body Side Inner Peregrine FormingTechnologies, supplier to GM, Chrysler and Ford Body Side Outer AutoDie International, leading Body Side supplier to Chrysler, also supplying Ford and GM Rear Structure Fab All Manufacturing, commodity supplier to Ford Roof and Roof Side Rails Schaefer Hydroforming Company Name Address Number of Employees Autodie International 44 Coldbrook, Grand Rapids, Michigan, USA 700+ Major products Tools, Dies and Molds, Prototypes & Production Automated Systems Transfer Equipment Welding Fixtures Robotic Vision Systems Other Divisions Customers Major Equipment Progressive Tool WISNE Design WISNE Design - Die Technology WISNE Automation Eagle Engineering Freeland Manufacuturing + Others Ford Chrysler Tower Spartanburg Navistar Cambridge GM Jaguar BMW Karmax Haworth Presses up to 3000 t Bed Size to 200 x CMM 5 Axis Control Laser 1 Lamoine Machine System CNC Mills PDGS CGS CATIA Chapter 8 - Page 2

170 Company Name Address Number of Employees Peregrine Forming Technologies Groesbeck, Warren, Michigan, USA 160 Major products Prototype Tooling Stampings and Assemblies Doors Inner / Outer Cowls, Fenders, Deck Lids Roof Panels and Floor Panels Other Divisions Customers Major Equipment APG - Technical Services Battle Creek Stamping Warren Stamping Warren Assembly Ford GM Dana Tower Ogihara Honda Spartanburg Presses up to 1500 t Bed size to 192 x 79 3 CMM 5 Axis Control Laser Foundry 3 CNC Mills PDGS CGS CATIA Company Name Address Number of Employees Fab All Manufacturers 645 Executive Drive, Troy, Michigan, USA 95 Major products Prototype Tools Stampings and Assemblies Specializing in Underbody, Front Structures and Inner Structures Other Divisions Customers Major Equipment Hubert Group Sharp Mold Engine M & T Design Services Models & Tools GM Ford Chrylser AG Simpson Veltri Narmco Presses up to 1700 t Bed size to 144 x CMM 6 Axis Laser NC Machining CATIA PDGS CGS Unigraphics Chapter 8 - Page 3

171 Company Name Address Number of Employees Stickel GmbH Porschestrasse 2, D Loechgau 40 Major products Prototype Build Prototype Tooling, Prototype Stampings Low Volume Production Stampings and Subassemblies Other Divisions Customers Major Equipment None Audi BMW Mannesmann Mercedes Benz Opel AG Porsche AG Presses up to 800 t Bed sizes up to 2m x 3m 3D Laser CMM Equipment CATIA CGS Company Name Address Number of Employees Schäfer Hydroforming, Schuler Auf der Landerskrone 2, D Wilhelmsdorf 135 Major products Hydroforming Presses (Development, Fabricating) Prototype and Production Parts Technology Development (Active Hydro Mec) Other Divisions Customers Major Equipment Tool Shop FEM Forming Simulation Hydroforming Componenets Audi Aerosmith GM Benteler Porsche Hydroforming presses to 3000t t under Construction High Speed Miling Prebending Equipment Chapter 8 - Page 4

172 8.2 Simultaneous Engineering In order to achieve the optimal design from a manufacturing and assembly standpoint, reviews were held with the suppliers and the assembly facility to evaluate all designs six months prior to design release. Each supplier was represented by specialists in CAD/CAM, tool making and manufacturing. Every detail was reviewed for formability, spring back issues, aesthetic consideration, tolerance control and assembly issues. In addition to the part suppliers, steel companies also attended these sessions in order to discuss and resolve any material issues. These reviews continued after design release, primarily in the suppliers facilities, but in addition to the design for manufacture and design for assembly, the reviews also included the supplier maintaining quality and timing plans Part Manufacturing Feasibility Introduction At the request of the ULSAB Steel Consortium and PES, Phoenix Consulting Inc. has assisted in the investigation and documentation of the manufacturing feasibility of the ULSAB components. The study includes the following objectives. Demonstrate that the processes used to fabricate the ULSAB components meet the following conditions:, Used design intent materials., Can repeatedly produce parts that meet dimensional requirements., Can repeatedly produce parts that meet formability requirements. Demonstrate that through continuous improvement, these processes can be evolved to production capable processes., Mechanisms are in place and are being followed to address manufacturing feasibility concerns., Action plans have been developed to address remaining barriers to production capability. Chapter 8 - Page 5

173 Demonstrate that state of the art methods and technologies have been used to develop the demonstration hardware processes, such as:, Forming Simulation., Early Steel Involvement., Dies and fixtures developed from CAD, CNC Machining and CMM Inspection. Overall Assessment Although the components of the ULSAB body structure certainly present a significantly greater challenge to production capability than a conventional design, we are convinced that these components can be fabricated with production capable processes under the following conditions: 1.The process of continuous improvement that has been undertaken by Porsche is continued, including additional soft die tryout and minor product revision. 2.With the use of the more sophisticated press equipment that can be made available in hard tool construction: Multiple Nitrogen Cushions, Toggle Presses and with the superior surfaces encountered in hard tooling. 3.With the implementation of further enhancements in materials, blank development and binder development. The team assembled to fabricate these components has made excellent progress along the learning curve of fabricating with high strength steel and laser welded blanks, advancing the state of the art. The prototype processes have undergone significant continuous improvement toward production capability Documentation Overview The components on the ULSAB body have been classified into three levels of difficulty or criticality. Level C being the most critical, level B the next most critical and all other parts are level A. The extent of documentation provided for a given component has been determined accordingly. The purpose of these documents is to validate the objectives outlined in the introduction. These documents have been assembled into a notebook that can be provided through the ULSAB Consortium. Chapter 8 - Page 6

174 These documents are described below, followed by a list of B and C level parts. In the pages that follow is an example of the detailed summaries for each individual B and C level part that can found in the notebook. Level A - Non Critical Material Characterization. This validates that the parts are made of material that meets structural requirements and that these materials can be worked into the forms of the respective parts. Level B - Moderately Critical. All Level-A requirements plus the following: Strain Analysis (Circle Grid and or Thickness Strain): Demonstrates that a formability safety margin exists and that parts are not merely split free. The goal and conventional buy off requirement is a 10% safety margin. These Strain Analyses are the responsibility of the Steel Vendors as part of the Early Involvement Program. They should include material properties of metal used to form the evaluated panel and the associated press conditions. This information is documented in AQP Parts format. Process Set Up: After extensive tryout, die shops have arrived at, and documented, optimum press conditions that will repeatedly yield quality panels. These Press Conditions along with other details of die set up are documented on Set Up Sheets. These Set Up Sheets can serve as baseline for further continuous improvement to develop production capable processes. Part submission warrants: These certify that prototype parts meet dimensional requirements. Chapter 8 - Page 7

175 Level C - Most Critical: All level A and B requirements, plus the following. CMM Reports: Computerized measurement of dimensional integrity. Development Logs: Show that state of the art methods and technologies were used to develop prototype processes and that these processes are undergoing a continuous improvement of evolution toward production capable processes. Proposed Production Process: This is the capstone of the above efforts. It is the culmination of lessons learned in prototype tryout and a demonstration of Porsche s confidence that the next step of setting up production processes can be taken. Forming Simulation: Finite Element Analysis based on CAD data was used to identify formability concerns before the construction of tools. B and C Level Parts Part Name Part Number Die Shop Level Pan Front Floor 040 Peregrine C Panel Rocker Inner 042 / 043 Peregrine C Panel B-Pillar Inner 064 / 065 Peregrine C Rail Rear Inner 046 / 047 Fab All C Rail Rear Outer 048 / 049 Fab All B Panel Wheelhouse Outer 070 / 071 Fab All B Panel Body Side Outer 060 / 061 Autodie C Member Dash Front 026 Stickel C Panel Skirt (& Shock Tower) 096 / 097 Stickel C Rail Front Inner 010 / 011 Stickel B Rail Front Extension 012 / 013 Stickel B Panel Dash 021 Stickel B Member Kick Up 091 Stickel B Rail Side Roof 072 / 073 Schaefer C Panel Roof 085 Schaefer B Spare Tire Tub 050 Stickel B Chapter 8 - Page 8

176 Documentation Responsible Format Parts Forming Simulation Steel Co. Steel Co. Report Select Parts Strain Analysis (Circle Grid, Thickness Strain) Steel Co. AQP B & C Steel Co. Material Characterization and Phoenix AQP A, B & C Process Set Up Steel Co, Die Shops Phoenix Summary & (Set UP Sheets) and Phoenix Die Shop Set Up Sheet B & C Proposed Production Process Porsche & Phoenix Process Sheet C Certification of Dimensional Die Shops Die Shop Form B & C Integrity (Warrant) Die Shops CMM or Checking C Inspection Report Fixture Report Development Log. Demonstrates state of the art procedures used to develop capable prototype processes & action plans for Die Shops Die Shop Log C making processes production capable. Observations and Recommendations Phoenix Phoenix Summary B & C Summaries of individual B and C level parts. On the following pages you will find an example of the documented data. Included will be: 1.Summary page, including observations and recommendations. 2.Part diagram. 3.Documentation checklist, listing and/or summarizing required documentation. 4.Material characterization sheet. 5.Forming limit diagram (part of strain analysis). NOTE: Complete documentation for all A, B & C level parts is contained In a separate report obtainable through the ULSAB Consortium. Chapter 8 - Page 9

177 Pan Front Floor Part Manufacturing Feasibility Summary The process involves first forming the front of the panel down, then the middle of panel the down and finally the rear of the panel up. This had to be done in separate operations for several reasons. One was press bed size. Another was the fact that all these areas are on separate levels and proper control of metal cannot be obtained without a more elaborate process involving nitro cushions and dydro units. The availability of these resources for production will enable a reduction in the number of operations, which will be necessary to reduce the total number of operations once trim and flange dies are added. Trimming and flanging is currently performed by laser and hammer form and will require cams in production due to the orientation of some of the trim and flange lines. Marginal strains detected in tryout and GD&T (geometric dimensioning & tolerancing) issues would have to be reassessed after implementing the recommendations below. Recommendations Based on Documentation Checklist Investigating grade change to a dent resistant steel that meets yield strength requirements but has a higher n-value. A dry film lube trial is also recommended. Consider use of a wider blank. This will allow for better control of metal outside of the kickup area by adding a more gradual transition in the addendum and binder. This may also enable the use of patches of higher formability metal where they are needed the most. This exercise would be well worth the effort, considering the portion of overall weight represented by the floor pan, and the challenging forming characteristics associated with it. Consider ways of forming embossed areas as late as possible in the process, either by using restrike die or by delayed action in draw dies, to avoid metal locking on and/or skidding over embossed area when it is required for feeding deep formations. Forming Simulation of first draw predicted wrinkling in tunnel near kickup. This is one of the areas where wrinkling was encountered in tryout. Chapter 8 - Page 10

178 Marginal Forming Strains at locations #2 and #15. Second Form First Form #15 Third Form #2 Increase blank width and implement smooth transition & drawbar. Embossments impede metal flow; result in double draw lines. Implement laser weld for wider blank. Chapter 8 - Page 11

179 ULSAB Part Manufacturing Feasibility Study Documentation Checklist Leve Part Part Name Supplier Spc Yield Coating Blank l # Thk Strength C 040 Pan Frt Floor Peregrine 0.7 mm 210 MPa 60G60GU Rectangle Document Format Status / Summary Forming Simulation Steel Co LS-Dyna3D simulation of 1st draw predicted significant wrinkling in the step area of part near the tunnel. This is one of the areas where wrinkling was encountered in tryout. The other areas occurred mainly during subsequent Strain Analysis Material Test Press Conditions Material Test Final / Conam Process Set Up Proposed Production Process Dimensional Check Dimensional Check Development Log AQP operations. Reports 40_D1.TXF (First Form) & 40_D3.TXF (Third Form) Safety Margin = 3%. Dry film lube trial suggested. Marginal Strains (#2, #15) need to be re-assessed after implementing blank config, binder and die process improvements. Included in AQP. Also see Process Set Up below. AQP Samples shipped to Conam on 12/11/97 Peregrine Warrant CMM Report Peregrine Set Up Sheet summary: Blank Size = 1829mm x 2057mm 1) PreDraw = Three piece stretch forms tunnel and kickup 2) Draw = Single Action with Upr Binder on Nitro forms deep pocket at rear of kickup 3) Three piece stretch forms shape at rear of panel 4) Flange. Flange at kickup is hand formed. Would have to be Cam Flanged in production. All trimming is by laser. Form #1 Ram = 1000 ton Binder = 160 ton ( psi) Lube = Quaker Prelube Form #2 Ram = 400 ton Binder = 100 ton Lube = Super Draw Form #3 Ram = 400 ton Binder = 200 ton (toggle press) Lube = Super Draw 1) Draw 2) 1st Trim 3) Re-strike 4) Form/Cam Form 5) Final Trim/Cam Trim Included CMM detected points that deviated from nominal by more than +/- 0.5 mm, however all were vertical and attributable to part length and flexibility, or hammer formed flanges. No difficulty experienced in assembly. Simultaneous Engineering procedures were used to develop the process, and continuous improvement was implemented to evolve the process toward production capability. Supplier concerns were fed back to Porsche and product revisions were subsequently implemented. Summary of development history and log of product changes is included. Also included is sketch of part showing significant manufacturing related changes. Chapter 8 - Page 12

180 Chapter 8 - Page 13 Engineering Services, Inc.

181 Chapter 8 - Page 14

182 Chapter 8 - Page 15 Engineering Services, Inc.

183 8.4. Quality Criteria The quality assurance system utilized on the ULSAB project followed the same standards as normal automotive practices. The key elements of control were: Material Engineering levels Process control Dimensional accuracy Parts submission Material: All material received was checked for dimensional accuracy by the part suppliers, the steel suppliers provided the material characterization data which was verified by an independent laboratory. Additionally, Porsche checked the material for weldability. Engineering Levels: A strict engineering change control system was implemented for this program. At each weekly review meeting all product levels were checked against the design status to insure compatibility. Suppliers were not allowed to implement any change without the authorization of PES. Process Control: As previously stated, the components were produced to production intent standards. Therefore, to insure this occurred, regular audits of the process were undertaken. Dimensional Accuracy: For each component, automotive standard checking fixtures were produced. These fixtures were used throughout the development process to provide verification of dimensional accuracy. Additionally for all major parts, the contract with the suppliers called for two fully CMM checked samples. As further assurance, where possible, match checks were undertaken to insure fit and function for the assembly process. Parts Submission: The approval process was based on PPAP (Production Part Approval Process) as outlined in QS 9000 guidelines. Before any part was shipped, the supplier had to provide documentation that showed all material, engineering, process and dimensional controls had been completed and met with the specifications set within the program. Chapter 8 - Page 16

184 9. DH Build Engineering Services, Inc.

185 9. DH Build 9.1. Introduction After ULSAB Phase 1 was successfully completed, the ULSAB Consortium decided to proceed with the ULSAB program into Phase 2. This involved proceeding from a conceptual study to the real world hardware, whereby the predicted mass savings and improved performance could be proven by actual product. Due to the experience in laser welding, Porsche s R & D Center in Weissach, Germany was chosen for the execution of the 13 DH builds. Figure Prototype Shop Chapter 9 - Page 1

186 9.2. Joining Technologies Laser Welding For more than 10 years the laser has shown its production capability. The first auto body application was the blank welding of the floor panel for the Audi 100. Laser welding in the assembly process was first brought into a production plant by BMW for the roof welding of its former touring model 3 series and Volvo for the roof welding of the 850 model. Since then, especially during the last three years, an increasing number of auto manufacturers have installed laser welding equipment within their production lines. Today laser welding applications in production plants are utilized all over the auto body, such as the front end, under body, closure panels and roof panel. Roof Roof Audi Audi BMW BMW Ford Ford GM GM Mercedes Mercedes Opel Opel Renault Renault Volvo Volvo Volkswagen Volkswagen B/C B/C Pillars Pillars Audi Audi Mercedes Mercedes Decklid Decklid / Tailgate / Tailgate BMW BMW Daihatsu Daihatsu Honda Honda Opel Opel Suzuki Suzuki Volkswagen Volkswagen Hood Hood Opel Opel Volvo Volvo Doors Doors Honda Honda Porsche Porsche Front Front Structures Structures BMW BMW Mercedes Mercedes Laser welding applications on production auto-bodies Fig Laser Welding in Assembly Chapter 9 - Page 2

187 The major reasons for using laser welding is the predominantly high static and dynamic strength of the joints, one side weld access for the welding equipment, small thermic impact zone and good aesthetic look at the joint area. The total length of the laser welding seams for the assembly on the demonstration hardware is meters. 1. Rail Front Outer to Rail Front Inner 2. Rail Fender Support Inner to Rail Fender Support Outer 3. Panel Body Side Outer to Panel A-Pillar Inner Lower 4. Rail Fender Support Outer to Panel Body Side Outer 5. Panel B-Pillar Inner to Rail Side Roof 6. Bracket Member Pass Through Lower to Member Pass Through 7. Panel Wheelhouse Inner to Rail Side Roof 8. Panel Back to Rail Rear Inner and Rail Rear Outer 9. Panel Dash to Rail Front Extension 10. Panel Cowl Upper to Panel A-Pillar Inner Lower 9 (3) (12) (14) Panel B-Pillar Inner to Panel Rocker Inner 12. Panel Roof to Panel Body Side Outer 13. Rail Side Roof to Panel A-Pillar Inner Upper 14. Panel Body Side Outer to Rail Side Roof 15. Panel Package Tray Upper to Support Package Tray 16. Support Panel Rear Header to Rail Side Roof 17. Panel Roof to Rail Side Roof 18. Member Pass Through to Brkt Member Pass Through Upr Frt & Rear 19. Rail Rear Outer to Rail Rear Inner 20. Panel Package Tray Upper to Panel Gutter Decklid Figure Laser Welding on ULSAB Demonstration Hardware Chapter 9 - Page 3

188 Spot Welding Spot welding is for all OEMs a well-experienced, reliable, affordable joining technique for steel auto bodies, even with zinc-coated steel materials. Porsche, for example, has been producing cars since 1977 with 100% zinc coated steel sheet metal and was the first company in the world practicing this. Now, more and more OEMs are switching to 100% zinc coated materials to improve corrosion protection and to give a long time anti-corrosion guarantee. Also for ULSAB, 100% of the material is double side zinc coated. control unit power unit transformer current measurement voltage measurement Figure Configuration of a Welding System Porsche s R & D Center Body Assembly Facility utilizes computer controlled medium frequency (1000 Hz) welding equipment. This system uses calibration to ensure that the welding current is maintained at a constant level. Thereby providing a good weld without disturbances and achieving optimum settings for welding time, welding current and electrode force. Having established the optimum setting, the data is stored in the computer enabling the use of the control mode to ensure all subsequent welding operations achieve the same optimum integrity. Chapter 9 - Page 4

189 weld current Engineering Services, Inc. These control processes inevitably necessitate fast welding current sources. This requirement is fulfilled by medium frequency inverters with a response time of one millisecond at an inverter frequency of 1000 Hz and by the substantially faster transistor DC technology. AC welding operation (50 Hz) weld current medium frequency inverter welding operation (1000 Hz) Comparison of the control response of thyristors and inverter controllers Figure The system is sensitive to: main voltage fluctuations shunts electrode wear (automatic stepper function) electrode force fluctuations small edge distances welding splashes changes from two sheet to multiple sheet welds Chapter 9 - Page 5

190 The control process compensates the various influencing factors by increasing or reducing the current strength and extending the welding time. Extension of the welding time can be limited. Welding splashes are monitored via output of an error message, with optional shutdown of the welding current. Optimum adaptation to each weld spot guarantees that the required strength for weld joints is maintained throughout broad ranges. Figure Medium Frequency Spot Welding Equipment Spot welding is used on ULSAB in all areas with suitable weld access and normal structural loads. The assembly of the demonstration hardware uses 2,126 spot welds. Chapter 9 - Page 6

191 Active Gas Metal Arc Welding (MAG) Active Gas Metal Arc Welding, or similar joining techniques, is used at all OEMs in locations with no weld access for spot welding or in areas with high stresses due to its strong structural behavior in comparison to spot welding. The disadvantages of this process, like slow welding speed, big heat impact zone, and pollution by weld fumes, especially with zinc coated materials, forced many OEMs to reduce it to a minimal amount. The targets for ULSAB were established to minimize the MAG welding seams. MAG welding is only used on the ULSAB body structure at locations without weld access for spot and laser welding. In total, there are 1.5 meters of MAG welding on the DH structure Panel A-Piller Inner Lower to Panel Cowl Upper 2. Door Hinges to Panel Body Side Outer 3. Door Hinges to Panel B-Pillar Inner 4. Door Hinges to Panel A-Pillar Inner 5. Support Package Tray to Rail Side Roof 6. Bracket Roof Rail Mount to Rail Side Roof 7. Bracket Member Pass Through Lower to Rail Side Roof Figure MAG Welding on ULSAB Demonstration Hardware Chapter 9 - Page 7

192 Adhesive Bonding The ULSAB steel sandwich material cannot resist the high temperatures during the painting process for body structures. Therefore this material is only suitable for parts which are assembled to the body after the painting procedure. Another factor is the non-weldability of the ULSAB sandwich material. So for the two parts on ULSAB made of steel sandwich adhesive bonding is the chosen joining technology. It has not only a structural function, it also provides sealing. The two panels made from steel sandwich material are the Panel Dash Insert (Part No. 022) and the Panel Spare Tire Tub (Part No. 050). Figure Bonding at Panel Dash Insert Chapter 9 - Page 8

193 In the production line, the panel dash insert will be assembled to the painted body structure as part of the instrument panel module. This includes the instrument panel, steering column, air conditioning system and pedal system. The panel dash insert is adhesive bonded and additionally bolted to dash panel. The bolting is necessary to keep the part in position until the bonding material is hardened. The panel spare tire tub will be assembled to the painted body structure as a module including the spare tire and the repair tools. The module is bonded to the structure. The operation does not require additional fixturing. The bonding material is a two component, non-conductive, high modulus, high viscous, chemically-curing polyurethane adhesive/sealant that cures almost independently of temperature and moisture. It is Betaseal X 2500 produced by Gurit Essex. Figure Bonding at Panel Spare Tire Tub Chapter 9 - Page 9

194 Technical Data Basis Polyurethane prepolymer Color black Solids content >98% (GM 042.0) Flash Point >100 C Processing temperature ideal 10 C - 35 C Working time approx. 10 min. at 23 C/50% r.h. (Processing time) Sagging behavior good, non-sagging Ultimate tensile strength > 5.5 MPa (DIN ) Percentage elongation > 200% (DIN ) Combined tension (GM 021) > 4.5 MPa and shear resistance G-Modulus > 2.5 MPa W Specific electrical > 10 cm (volume resistivity) Abrasion resistance Extremely high Recovery (DIN ) approx. 99% Temperature stability - 40 C at 100 C (for short periods up to 140 C) Resistance to chemicals Highly resistant to aqueous chemicals, petrol (in cured conditions) alcohol and oils. Conditionally resistant to esters, aromatics and and chlorinated hydrocarbons. Preparation of bonding surface All bonding surfaces must be free of dirt, dust, water, oil and grease. In general, surfaces should be primed. Chapter 9 - Page 10

195 9.3. Flexible Modular Assembly Fixture System The body shop in Porsche s R & D Center used a highly flexible modular fixture system for the DH assembly. It is based on standardized units, which are adjustable in all directions. Figure Assembly Fixture Module There are many advantages of this fixture system. 95% of the elements in a fixture are from the standardized module system and can be used also for other car programs. Chapter 9 - Page 11

196 Figure 9.3-2a Assembly Fixture Module Detail Figure 9.3-2b Assembly Fixture Module Detail Chapter 9 - Page 12

197 The fixture design performed in CATIA was very efficient, because all models were accessible from the CAD data bank. Therefore, the construction time for assembly fixtures was reduced and modifications or corrections of existing assembly fixtures could be implemented rapidly. Figure Assembly Fixture - Bodyside Inner Subassembly Chapter 9 - Page 13

198 Porsche is using the flexible modular system in two ways. The first is the so-called shuttle system, which is related to the set-up pallets. The shuttles for different assemblies are stored in a shuttle magazine. During the assembly operation the shuttle is fixed on a set-up pallet. The changeover of various assembly shuttles on a set-up pallet is a very fast process. These assembly shuttles are mobile and can be used at different locations. Figure Assembly Fixture Shuttle on Setup Pallet Chapter 9 - Page 14

199 The second method is the utilization of a rolling device that supports the modular assembly fixtures independent from set-up pallets. These assembly fixtures work at any location. Figure Mobile Assembly Fixture - Shock Tower Front SubAssembly RH/LH Chapter 9 - Page 15

200 9.4. Design of Assembly Fixtures All fixtures are developed with a CAD system (CATIA) based on the existing design data. The CAD data models of the fixture system modules are available from a data bank. Figure Fixture Development on CAD System Figure CAD Data Modules of Fixture System Chapter 9 - Page 16

201 The DH assembly sequence is exactly the same as it is foreseen in the production plant. Due to the fact that in prototype productions no cycle time limit is given one fixture can be used for more joining operations than in a production line. This results in a drastically reduced number of assembly fixtures in relation to a production line. For the ULSAB assembly, the Porsche body shop used the following fixtures: Assembly Shock Tower Front Assembly Front End Assembly Floor Complete Assembly Under Body Complete Assembly Body Side Inner Assembly Body Complete An example of a fixture design is shown in Figure Figure Fixture Shock Tower Front Chapter 9 - Page 17

202 9.5. DH Build Assembly Team The Porsche BIW assembly team consists of the following personnel: 1 foreman 1 expert/deputy foreman 23 workers which include 5 with foreman s / technician s degree and 5 workers trained for CATIA Figure Body Shop Chapter 9 - Page 18

203 In a workshop space of 1200 m 2, the following equipment is installed: 12 setup pallets (6x3m) with surface measuring device 4 mobile welding machines, 1000 Hz with control equipment 5 mobile welding machines, 50 Hz with constant-voltage regulation system 5 overhead spot-welding devices with 3 secondary guns each and a 50 Hz Bosch control system 1 Rofin Sinar Laser device, 2.5 kw Two applications with special interest for ULSAB will be described in more detail. All spot welds on ULSAB were manufactured with a mobile Duering welding cart and a Matuschek medium-frequency inverter device with master control system. Figure Chapter 9 - Page 19

204 The welding gun changeover system allows a rapid change between different types of welding guns, whereby a special gun coding provides the correct weld parameters from an automatic program selection. Figure Weld Gun Station Chapter 9 - Page 20

205 The laser welding and laser cutting cabin is equipped with a KUKA KR 125 robot. The maximal load is 125 kg and the working range of 2410 mm. Figure Laser Cabin Chapter 9 - Page 21

206 The laser source is a Rofin Sinar CW 025 Nd:YAG Laser. The maximum output of 2500 W is transferred through a switching device with two outlets via two 15-m glass fibre cable of 0.6 mm diameter to the laser optic. Figure Laser Besides a laser cutting head three different types of laser welding heads are available. Figure Laser Picker Chapter 9 - Page 22

207 Figure Single Roller Figure Double Roller Chapter 9 - Page 23

208 Build of the Test Unit The construction of the test unit, internally called workhorse, started on May 26, 1997, and began testing on June 27, The following series of photographs shows steps of the assembly sequence of the test unit. Due to the extensive preparations, the construction worked out excellent, but there was still room for small improvements. Figure Rear Floor Subassembly Chapter 9 - Page 24

209 Figure Subassembly Front End Figure Subassembly Underbody Complete Chapter 9 - Page 25

210 Figure Subassembly Body Side Inner Figure Assembly Body Side Inner to Underbody Chapter 9 - Page 26

211 Figure Subassembly Body Side Inner with Underbody Figure Sub-Assembly Body Side Outer, with Body Side Inner and Underbody Chapter 9 - Page 27

212 Build of DH #2 to DH #13 After build and testing of the test unit, a design review meeting in Porsche s R & D Center was held with the experts in the fields of body design, safety, CAE calculations, parts manufacturing and body assembly. Ideas for improvements in respect to performance, parts feasibility, weld access and appearance were generated in this meeting. The next step was a redesign of the ULSAB body structure reflecting the ideas of the design review meeting. The CAE calculations of the changed FE model proved nearly the same performance. Now new parts were manufactured incorporating these changes in the construction of DH #2 to DH #13. Figure Demonstration Hardware #2 in Body Shop The build of DH #2 started on December 1, The assembly sequence for DH #2 to DH #13 remained the same as test unit. Chapter 9 - Page 28

213 9.6. Quality Body Quality Control Team The Porsche Body Quality Control Team includes the following personnel: 1 engineer 2 technicians 5 foremen 2 specialist workers In a working area of 300 m 2 the following equipment is used for body quality control measurement: 1 Stiefelmeyer double-column coordinate measuring machine (CMM) 1 Stiefelmeyer single-column manual measuring machine 1 Zeiss double-column CMM Figure DH #2 during Measuring Procedure Chapter 9 - Page 29

214 The general range of services includes: Part acceptance at supplier s premises Model acceptance at supplier s premises Body measurement Digitalization of data for design Trouble-shooting Prototype quality statistics Quality Control Measurements of DHs The basis for part and assembly quality was the early involvement of all relevant participants in the design and engineering process. Regularly simultaneous engineering meetings were established with designers, engineers, material suppliers, tool and part manufacturers and body shop personnel. The expert group defined locator holes, tooling holes and fixing points. To ensure excellent quality, these defined points were used for the complete process chain from parts manufacturing over subassemblies to final assembly. All manufactured parts were inspected by the supplier s quality control personnel and approved by Porsche specialists. The first proof of feasibility and design for manufacture was the successful construction of the test unit. This demonstration hardware was fully inspected by Porsche s quality control team. In total, about 200 different points on the ULSAB body structure were measured and compared to the original CAD data. The measured dimensions were, especially for a first time assembled body structure, in a close range to the nominal values. Chapter 9 - Page 30

215 Figure Measuring protocoll Nevertheless, the results of the test unit were used to develop modifications of the tools for part manufacturing and of the assembly fixtures for improved quality, meaning smaller tolerances for the following DHs. Each DH is or will be inspected to evaluate a quality statistic for the ULSAB program. Chapter 9 - Page 31

216 9.7. Conclusion The assembled demonstration hardware proved to be a successful execution of the body structure construction. The measured tolerances are in a comparable range in relation to average car programs. The challenges of laser welding in assembly, assembly of hydroformed parts, 90% high strength steel, and steel sandwich material, were mastered. The principle condition for success was the simultaneous engineering process. All project partners contributed to the realization of Phase 2 of the ULSAB program. Through early involvement in the project, all parties involved incorporated all of their expertise into the realization of the demonstration hardware. Figure Chapter 9 - Page 32

217 10. Testing and Results Engineering Services, Inc.

218 10. Testing and Results Scope of Work To prove the structural integrity of the ULSAB demonstration hardware, the following test procedures were executed as part of the ULSAB program in Phase 2. Static rigidity Static torsion Static bending Modal analysis 1 st Torsion mode 1 st Bending mode 1 st Front end lateral mode Mass DH mass in test configuration All testing work was performed at Porsche s R & D Center in Weissach. Fig Aerial View Chapter 10 - Page 1

219 10.2. Targets The main factors affecting the ride and handling of the vehicle are Noise, Vibration and Harshness, known as NVH behavior. To achieve the desired levels of comfort for the occupants, the vehicle body must have high static and dynamic rigidity. In other words, the auto body should have high stiffness. This is required because the increased rigidity improves the vehicle resistance to excitement caused by the drive train, the engine or by road conditions such as bumps and potholes. When excited, the car body vibrates at particular frequencies, called its natural frequencies, and also in a particular manner called its mode shape. The mode shapes are for instance on: global torsion mode, global bending mode and front end lateral mode. Another result of good rigidity would be minimal deviations in the dimensions of the body structure openings such as the hood, front door, rear door and deck lid under load conditions. These movements between the body structure and the closure panels often create sounds. Furthermore, it should be proven that the received numbers from the analysis by FE-calculations are in correlation with the results gathered by the testing procedure. Based on the current average of selected, benchmarked vehicles in Phase 1, the following targets for the ULSAB structure were established: Performance Targets Mass [ 200 kg Static torsional rigidity m13,000 Nm/deg Static bending rigidity m12,200 N/mm First body structure mode m 40 Hz NOTE: Structural performance with windshield and backlight; mass without windshield and backlight. Chapter 10 - Page 2

220 10.3. Static Rigidity Test Setup General The DH in full test configuration consists of the following parts: Welded Body Structure Bonded Windshield and Back Light Bonded and bolted Panel Dash Insert (Part-No. 022) Bonded Panel Spare Tire Tub (Part-No. 050) Bolted Reinforcement Panel Dash Brake Booster (Part-No. 115) Bolted Braces Radiator (Part-No. 188) Bolted Reinforcement Radiator Rail Closeout RH/LH (Part -No. 094/095) Bolted Reinforcement Radiator Support Upper (Part-No. 001) Bolted Tunnel Bridge Lower/Upper Bolted Brace Cowl to Shock Tower Assembly Figure DH with Bonded / Bolted Parts Chapter 10 - Page 3

221 The unpainted body structure was measured without front and rear suspension system. The body structure was held at four points: the front; at Panel Skirt RH/LH (Part-No. 096/097) and the rear; at Plate Rear Spring Upper (Part-No. 110). Along the front rails, the rockers, and the rear rails 12 stadia rods were attached. Twenty-four electronic feelers measured the movements of these rods. Aluminum panels with glass thickness were used to simulate the bonded windshield and backlight. Due to the fact that the related material property for rigidity and stiffness, the Youngs modulus, shows a close similarity for glass and aluminum. This can be done without compromising the test results, but taking advantages in timing and cost Static Torsion The DH was mounted to the test rig with rigid tubes. Two rear locations at the plate spring rear upper were constrained, while the load was applied to panel skirt RH/LH by a scale beam. Figure Test Configuration for Static Torsion Chapter 10 - Page 4

222 The measurements were taken with four different loads from M =1000Nm to t max=4000nm. M t Before starting the measuring procedure, the maximum load was applied to the DH to eliminate the sag rate Static Bending The DH was mounted to the test rig by rigid tubes. The four fixing points of the DH were constrained. The loads were applied to the center of the front seats and to the center of the two outer rear seats. Figure Test Configuration for Static Bending The measurements were taken with four different loads from F = 1000 N b (4 x 250 N) to F max = 4000 N (4 x 1000 N). b Before starting the measuring procedure, the maximum load was applied to the DH to eliminate the sag rate. Chapter 10 - Page 5

223 Results Static Torsion Figure DH on Test Rig for Static Torsion The torsional rigidity for the test unit in the configuration described in section is: With glass Without glass 21,620 Nm/deg 15,790 Nm/deg Chapter 10 - Page 6

224 20 15 Front Axle Test Unit Displacement Torsion Rear Axle 4000 Nm 3000 Nm 2000 Nm 1000 Nm Angle of Twist [min] Longitudinal Axis X [mm] Figure Torsion Lines 4 Load Cases with Glass In general, the graph plot is running harmonic. There is only a jump in rigidity between x = 3800 to x = This is related to the positive impact of the Member Pass Through (Part-No. 090) to the torsional stiffness. 0.4 Test Unit Gradient Torsion 0.3 Front Axle Rear Axle 0.2 Gradient [ /m Longitudinal Axis X [mm] Figure Gradient of Torsion Line with Glass The above graph shows the gradient of the torsion line. The disharmonies of the torsion line can be seen in a higher resolution. Chapter 10 - Page 7

225 The torsional rigidity for DH #2 in the configuration described in section is: With glass Without glass 20,800 Nm/deg 15,830 Nm/deg Front Axle DH #2 Displacement Torsion Rear Axle 4000 Nm 3000 Nm 2000 Nm 1000 Nm Angle of Twist [min] Longitudinal Axis X [mm] Figure Torsion Lines 4 Load Cases with Glass As expected, the results are very close to the test unit. This assumption is based on the test results without glass, because these are nearly identical (15,790 Nm/deg vs. 15,830 Nm/deg). Chapter 10 - Page 8

226 0.4 DH #2 Gradient Torsion 0.3 Front Axle Rear Axle 0.2 Gradient [ /m] Longitudinal Axis X [mm] Figure Gradient of Torsion Line with Glass The above graph shows the gradient of the torsion line. The disharmonies of the torsion line can be seen in a higher resolution. Chapter 10 - Page 9

227 To investigate the impact of several bonded and/or bolted parts, additional measurements in various test configurations were undertaken with the test unit. Test Configurations: 1. Full configuration as described in Section As 1, but without braces radiator (Part-No. 188) 3. As 2, but without radiator support upper (Part-No. 001/094/095) 4. As 3, but without bolted brace cowl to shock tower assembly 5. As 4, but without tunnel bridge Torsion Rigidity 110 Torsion Rigidity [%] Test Configuration Figure Torsion Rigidity Five Test Configurations As the numbers show, only the bolted brace cowl to shock tower assembly has a significant impact on the torsional rigidity of 6.3%. Chapter 10 - Page 10

228 Static Bending Figure DH on Test Rig for Static Bending The bending rigidity of the test unit in the configuration described in Section is: With glass Without glass 20,460 N/mm 17,150 N/mm Chapter 10 - Page 11

229 Front Axle Test Unit Displacement Bending Rear Axle 0.3 Vertical Displacement [mm] Longitudinal Axis X [mm] Figure Bending Lines 4 Load Cases with Glass 4000 N 3000 N 2000 N 1000 N The graph is running harmonic. There is only a local increase in bending rigidity between x = 3500 and x = This indicates a stiff joint between rocker and rear rails. Furthermore, Porsche relates this to the design of the side roof rail. 50 Test Unit Average Deviation Bending Deviation from the average [%] Front Axle Rear Axle Longitudinal Axis X [mm] Figure Deviation from the Average Bending Line with Glass The above graph shows the deviation from the average value of the bending line. The disharmonies can be seen in a better resolution. Chapter 10 - Page 12

230 The bending rigidity for DH #2 in the configuration described in Section is: With glass Without glass 18,100 N/mm 15,950 N/mm Front Axle DH #2 Displacement Bending Rear Axle Vertical Displacement [mm] N 3000 N N 1000 N Longitudinal Axis X [mm] Figure Bending Lines 4 Load Cases with Glass The bending lines show the same characteristics as for the test unit, but the absolute value decreased by 11%. The local increase between x=3500 and x=4200 is not so evident as it was on the test unit. This could be created by local modifications of the side roof rail and the rear rails for improved manufacturing. Furthermore, the material gage of the panel roof changed from 0.77mm to 0.70mm due to material availability problems for the test unit; this was also a factor for the decrease of the absolute value. Additionally Porsche has experienced that static rigidities of body structures differ by plus/minus five percent (5%) even under series production conditions. Chapter 10 - Page 13

231 Deviation from the average [%] Front Axle DH #2 Average Deviation Bending Rear Axle Longitudinal Axis X [mm] Figure Deviation from the Average Bending Line with Glass The above graph shows the deviation from the average value of the bending line. The disharmonies can be seen in a better resolution. Chapter 10 - Page 14

232 To investigate the impact of several bonded and/or bolted parts, additional measurements were undertaken: Test Configurations: 1. Full configuration as described in Chapter As 1, but without braces radiator (Part-No. 188) 3. As 2, but without radiator support upper (Part-No. 001/094/095) 4. As 3, but without bolted brace cowl to shock tower assembly 5. As 4, but without tunnel bridge Bending Rigidity Bending Rigidity [%] Test Configuration Figure Bending Rigidity Five Test Configurations As the numbers show, none of these parts display a significant impact on bending rigidity. The increase from test configuration four (4) to test configuration five (5) is caused by local effects of the tunnel bridge to the displacement of the rocker. This behavior was also noticed in other body structures. Chapter 10 - Page 15

233 10.4. Modal Analysis Test Setup A modal analysis describes the vibration behavior of a structure. Results of a modal analysis are the resonance frequencies of the specific structure and the corresponding mode shapes (how the structure vibrates). The ULSAB structure was suspended on a test rack held by rubber straps to decouple the test unit from the supporting structure of the test rack. In order to find the mode shapes and the resonance frequencies, energy is applied to the structure. The response of the structure (in general the acceleration at different points) is measured in relation to the input forces. From the contribution of each input force to each response value, the dynamic behavior of the structure is calculated. Figure Test Configuration for Modal Analysis In the case of the ULSAB, the body structure is excited by means of four electrodynamic shakers that are coupled to the corner points of the structure. Chapter 10 - Page 16

234 The simultaneous excitation with four shakers is necessary to provide good energy distribution into the structure and to minimize the influence of possible nonlinearities to the quality on the results. In addition, the torsion and bending modes of the body can be excited definitely. Torsion and bending are the most important global modes of a body structure. Each of the four shakers is driven by a computer-generated, statistical independent band limited (0 to 100 Hz) Gaussian random noise spectrum. The response of the structure is determined by measuring vibration transfer functions between the acceleration at each measurement point in three orthogonal directions and each driving force. Accelerometer HP 9000/700 LMS CADA-X DAC Interface ADC Interface Electrodynamic Shakers Power Amplifier Memory Charge Amplifier Aliasing Filter and Amplifier Figure Set-Up for Modal Analysis The global parameters of the structure, frequency and damping are determined thereafter by a Least Squares Complex Exponential (LSCE) fitting. Chapter 10 - Page 17

235 The modal displacement is calculated subsequently by fitting a Multiple Degree of Freedom (MDOF) model to the transfer functions in the time domain. The test configuration of the test unit was exactly the same as the testing of static rigidities described in section Results Figure DH on Test Rig for Modal Analysis Chapter 10 - Page 18

236 The global modes of the test unit in the described test configuration can be seen in the following chart: Test Unit Modal Analysis 70 First Modes [Hz] Torsion Bending Front End Lateral without glass with glass Figure Modal Analysis Results - Test Unit The dynamic rigidity of the ULSAB structure is remarkably good, as it was already indicated by the static test results. Windshield and backlight have a significant impact on the first torsion mode. The difference is in the same range, as known from other sedan body structures. The effect on first bending and first front-end lateral mode is relatively small. For the test configuration with glass, the first torsion mode and the first front-end lateral mode are coupled at 60.6 Hz. Chapter 10 - Page 19

237 Frequency Response Function Amplitude [(m/s2)/n] Test Unit Modal Analysis with Screens Frequency Response Functions, measured at the body corner points Power input by means of electrodynamic shakers at the body corner points Test Unit Modal Analysis with Screens First Bending 62.4 Hz First Torsion 60.6 Hz Bending 63.5 Hz Frequency [Hz] Corner Points Front Left Front Right Rear Left Rear Right Figure Frequency Response Functions - Test Unit The graph plot above shows the frequency response functions, measured at the four driving points. Second bending mode at 63.5 Hz occurs mainly in the rear; whereas the first bending mode occurs in the front and rear of the structure. Chapter 10 - Page 20

238 The global modes for DH #2 in the described test configuration can be seen in the following chart: DH #2 Modal Analysis 70 First Modes [Hz] Torsion Bending Front End Lateral w ithout glass w ith glass Figure Modal Analysis Results - DH #2 The dynamic rigidity of DH #2 is in the same range as the values of the test unit. The front-end lateral mode changed remarkably. This is created by the change of the material gauge of the rail fender support inner from 0.9mm to 1.2mm. The torsion mode and bending mode without glass decreased slightly, but with glass, the loss of dynamic rigidity is compensated. Chapter 10 - Page 21

239 Frequency Response Function Amplitude [(m/s2)/n] 4 Measurement Points: 3.8 First Bending 63.9 Hz Body Corner Points Driving Points: 3.2 Body Corner Points Front Left Front Right 2.4 First Torsion 60.1 Hz Rear Left Rear Right Project: Test: Date: ulsabdh2 ULSAB_DH2_mS Vehicle: ULSAB DH2 0.2 Body Structure 0 with Screens Frequency Hz DH #2 Modal Analysis with Screens Frequency Response Functions, measured at the body corner points Power input by means of electrodynamic shakers at the body center points Figure Frequency Response Functions - DH #2 The graph plot above shows the frequency response function, measured at the four driving points. The amplitude of the first bending increased in relation to the test unit. This is in correlation with the decrease of the static bending rigidity. Additional modal analysis was conducted on the ULSAB structure, to investigate the influence of several bolted and/or bonded parts. Test configurations: 1. Full test configuration as described in chapter As 1, but without bolted brace cowl to shock tower assembly 3. As 2, but without braces radiator (Part-No.188) 4. As 3, but without tunnel bridge 5. As 4, but without radiator support upper (Part-No. 001/094/095) Chapter 10 - Page 22

240 Modal Analysis First Modes [Hz] Test Configuration Front End Lateral Torsion Bending Figure Modal Analysis Five Test Configurations The influence of the bolted brace cowl to shock tower assembly on the front-end lateral mode of 13.6 Hz is evident. Test configuration 5 shows an improvement in the front-end lateral mode, but this is mainly caused by the influence of the mass of assembly radiator support. The other modifications have no evident impact on dynamic rigidity. Chapter 10 - Page 23

241 10.5. Masses in Test Configuration A crane with a scaled load cell balanced the DH. Figure DH #2 on Crane The measured mass in full test configuration included the mass of the bolted brace cowl to shock tower assembly and tunnel bridge, which were installed for testing only (see Test Configurations). The mass of Windshield and backlight were not included. The mass in this test configuration was the following: Test Unit kg DH # kg *This mass includes 2.86 kg for the bolted brace cowl to shock tower assembly and tunnel bridge The calculated mass for non-constructed reinforcements and brackets has to be added (see Chapter 5 on Design and Engineering). Chapter 10 - Page 24