Mass Efficient Architecture for Roof Strength - MEARS

Transcription

1 Mass Efficient Architecture for Roof Strength - MEARS Shawn Morgans Ford Motor Company

2 Project Team Members Chaired by: Shawn Morgans (Ford Motor Company) Automotive Company Members: SPARC Mentor: Omar Faruque Ford Motor Company Henry Hausler Ford Motor Company Rama Koganti Ford Motor Company Staff Members/Consultants: Ben DeRocher General Motors Corp. Pat Villano A/SP Joe Polewarczyk General Motors Corp. Chuck Potter AISI Bill Croasmun Chrysler Gagan Tandon Hoff and Associates John Huhn Hoff and Associates Steel Company Members: Tim Montroy AK Steel Corporation Ravir Bhatnagar ArcelorMittal Liang Huang ArcelorMittal Min Kuo ArcelorMittal Yu-Wei Wang Severstal North America Inc. Srini Laxman Severstal North America Inc. Guofei Chen U.S. Steel

3 Project Goals Develop designs for the B-Pillarless body architecture that is capable of achieving the loads specified in the NPRM for FMVSS 216. Structure must support a load of 2.5 times the maximum unloaded vehicle weight. Maximum load requirement must be achieved before there is contact between a 50 th Percentile Hybrid III Dummy and any component of the vehicle. Minimize the weight impact to the vehicle with the use of AHSS materials and structural design concepts. Best solution selected based on weight efficiency, cost effectiveness, and ease of manufacturing.

4 Project Approach Develop three design alternatives to meet proposed roof strength requirements. Concept 1: AHSS Intensive Conventional Design Concept 2: Hydro-form Intensive Design Concept 3: Hybrid AHSS / Structural Inserts Utilize non-linear FEA and optimization software to develop the most mass efficient solution to achieving roof strength requirements. Exceed the load requirements specified on the FMVSS 216 NPRM. 3 x MUVW Account for test and vehicle variability. Achieve load before 4.5 inches of displacement.

5 Project Approach Modify vehicle structure within the confines of the existing Class A panels and inner panel surfaces through the use of: Steel grade and gauge Tailor welded blanks Hydro-formed components Hot stamped panels Structural foam Composite inserts (localized reinforcements)

6 Steel grades included on the study were established by availability in the NA market AHSS and UHSS DQSK DR 210 BH 250 HSLA 250 HSLA 350 HSLA 400 DP 590 DP 780 DP 980 TRIP 780 Boron 1550

7 Baseline Model Assessment

8 Baseline Model Assessment

9 Concept Description Concept 1 AHSS Intensive Architecture Conventional stamped and welded structure High use of AHSS DP600 DP780 DP980 Boron Concept 2 Hydro-Form Intensive Architecture Based on Concept 1 Design with reduced gauge and grade Added tubes shown in picture below Tubes spot welded to structure with brackets that are GMAW to tube Tube material is DP780 Hydro form tube from A-Pillar to C- Pillar. 1-7/8 inch tube with 1.5 mm thickness Hydro form tube from C-Pillar to C-Pillar 2.5 inch tube with 1.5 mm thickness

10 Concept Description Concept 3 Hybrid Architecture Developed from the Concept 1 Model with reduced gauge and grades Multiple insert types designed and evaluated Welded Steel Structural Foam Bonded In Nylon Reinforcements Bonded In Nylon Reinforcements performed the best at the following locations A-Pillar Lower A-Pillar Upper / Roof Rail C-Pillar Upper / Roof Rail Nylon Inserts

11 Final Design Phase 1 Final Design Selection S.No Weighted Rating developed for solutions from each concept Based on weight impact, variable cost, manufacturing impact, and ability to repair Nylon Inserts and Steel Inserts performed equally Nylon Inserts selected due to lower weight increase over baseline model Concept Load Mass Factor [kgs] Cost Rating Weighted Manufac Mass Cost turability Repair Rating Stamping Intensive $ Hydroform intensive $ A1 3 A2 Weight Factor > Steel Inserts-Tube in C-Pillar Steel Inserts- Stamped C-Pillar Rnf $ $ B Nylon Inserts (Drop-in) $ C BetaFoam (Injected) * 8.4 $

12 Final Results Phase 1 Optimized Design Force Deflection Curve Strength to Weight Ratio: 3.06 Mass Increase: 1.22 kg 63% Load Increase

13 Phase II Tasks 1. Continue the optimization of Final Phase I Model 2. Demonstrate correlation between CAE and actual test of composite reinforcements 3. Investigate the impact of component geometry on roof strength performance 4. Utilize continuous joining methods to enhance performance 5. Conduct part feasibility studies 6. Develop costs for proposed changes/adds

14 Alternate Steel Design Study conducted to investigate the possibility of meeting the objectives without the use of Composite Inserts Investigations into the influence of several key areas of the structure were conducted: B-Pillar Roof Bow A-Pillar and Front Header Joint B-Pillar Front Header Rear Header Roof Rail Determined that the C-Pillar and Roof Rail had the most significant contribution to the load-carrying capability of the structure. The A-Pillar and Headers played a lesser role. Design updated with a steel C-Pillar Reinforcement and subjected to optimization

15 Phase II Optimized Steel Solution Design was modified to: Include a C-Pillar Reinf. Rear Header Outer Material grade and gauge changes Model Load Factor Greenhouse Mass Steel Component Mass Composite Insert Mass Phase I Final Concept Model kg 30.9 kg 6.5 kg Phase II Alternate Steel Design Concept # kg 38.8 kg N/A Steel Structure Components Thickness (mm) Material (Steel) Boron1550 Boron1550 Boron1550 BH250EG BH250EG HSLA350 DR210 DP600 HSLA350 Boron1550 DP1000 Boron1550 Boron1550 Boron1550

16 Phase II Optimized Steel Solution

17 Composite Inserts Model Solid tetrahedral mesh representations Encompassed the inner and outer components volumes A-Pillar through Roof Rail Section C-Pillar Sections

18 Insert Design Optimization Reduction in the Size of the Composite Reinforcements was Required to: 1. Minimize Weight Impact 2. Minimize Cost Impact 3. Improve Manufacturing Feasibility Design Space was sectioned off into 100mm areas and subjected to volume optimization. Following volume optimization, the tet mesh was converted back to nylon rib inserts in order to verify the optimization results.

19 Phase II Optimized Solution vs. Phase I Optimized Solution Phase I Optimized Solution Composite Reinforcement Location Comparison Phase I: Composite Reinforcements: 6.5kg Phase II: Composite Reinforcements: 4.6kg Savings of 1.9Kg Phase II Optimized Solution

20 Phase II Optimized Solution vs. Phase I Optimized Solution Optimization of the Wall Thickness of the Nylon Structure Further Reduced Weight Insert 2 Insert 3 Insert 1 Insert 4 The composite reinforcements in the Phase II Optimized Solution are 1.9kg lighter than the Phase I Optimized Solution.

21 Phase II Optimized Steel with Composite Reinforcement Total Weight Save over Phase I = 5.2 Kg 4.0 Kg lighter than Donor Vehicle

22 Phase II Optimized Solution vs. Phase I Optimized Solution Load vs. Displacement Normalized Load Displacement (mm) Phase II Steel and Nylon Solution Phase I Baseline Model

23 CAE vs. Actual Correlation Studies for Composite Reinforcement Team elected to use existing data from Nylon Insert Supplier for correlation study CAE and actual 3-Point Bend Test data collected and compared Effects of failure criteria on model results were reviewed Tensile failure criteria did not represent actual data Compression and shear failure criteria correlate well to physical data Physical Test Simulation

24 CAE vs Actual Correlation Studies for Composite Reinforcement CAE under predicts the peak load Energy prediction varied with inclusion of failure criteria

25 CAE vs. Actual Correlation Studies for Composite Reinforcement Full Vehicle FMVSS216 Testing Performed on a production vehicle Tested with and without Composite Nylon Inserts With Composite Nylon Inserts, stiffness improved by 30% Analytical prediction and testing showed similar trends Partial Bonding Data Collection Drop in roof strength observed due to Partial Bonding Analytical Predictions when correlated show similar behavior

26 Insert - Partial Bond Study Several studies conducted with the random removal of 20% of the bond surface. Slight degradation in peak load 2.93 vs. 3.0

27 Linear C-Pillar Optimization Apply linear optimization methodology to create an insert that provides stiffness of the nylon insert with the use of less material LOWER COST and WEIGHT Extracted loads at this section Linear Optimization is evaluating this portion of the c-pillar Extracted Section Loads are applied at the top portion of the model. Insert is modeled as tet mesh. The bottom portion is constrained where the insert ends in all DOF 1-6.

28 Linear C-Pillar Optimization Volume Topology Based Shape Optimization applied to the C-Pillar design space led to 2 potential solutions A C-Channel and tube reinforcements (2mm thick Boron Material) were modeled to reflect the linear optimization solution. A Z-Channel and tube reinforcements (2mm thick Boron Material) were modeled to reflect the linear optimization solution.

29 Linear C-Pillar Optimization Results suggest that a modification (increased) to the loads applied during the linear optimization process is required May have been more successful if this approach was used to develop the rib pattern in the Composite Reinf.

30 Weld Bonding Dow BM73352 Adhesive added in joints between components of the green house Existing welds retained Resulted in a negligible increase in max load over base line model Base Line Model: Weld Bonded: 2.96 X MUVW 2.97 X MUVW

31 Continuous Welding Doubled the number of welds in the green house to represent continuous bonding 8% increase in max load over base line model Base Line Model: Doubled Spot Welds: 2.96 X MUVW 3.19 X MUVW Will allow for further optimization to reduce vehicle mass

32 Weld forces extracted from the model for all green house welds Retained only the welds that reached a load 5kN Reduced the number of added welds from 770 to 48 4% increase in max load over base line model Base Line Model: Weld Bonded: Weld Optimization Studies 2.96 X MUVW 3.07 X MUVW

33 Optimized Final Model Achieved load target of 3.0 within displacement limits with a 4.4kg reduction in mass Model Load Factor Greenhouse Mass Steel Component Mass Composite Insert Mass Phase I Final Concept Model kg 30.9 kg 6.5 kg Phase II Composite Nylon Insert Steel Design Concept # kg 27.6 kg 4.6 kg Phase II Composite Nylon Insert Steel Design Concept # kg 27.1 kg 4.6 kg Steel Structure Components Thickness (mm) Material (Steel) Boron1550 Boron1550 DR210 BH250EG BH250EG HSLA400 HSLA400 BH250EG DQSK DP Boron Boron a 1.3 Boron b 0.8 DP590

34 Linear Based Optimization Load case of FMVSS 216 test applied to a linear model to investigate the effectiveness of: Topology Optimization Volume Topology Optimization Free Shape Optimization Attempt to quickly assess the performance of a structure and to highlight areas of possible concern Linear model was much stiffer due to the absence of plastic deformation

35 Linear Topology Optimization Determine design sensitivity to gauge of the components within the baseline model Results indicate the C-Pillar area shows strong influence on roof strength as predicted in the non-linear analysis Indicates that the use of linear topology optimization up front in the design phase to define load paths will aid in the development of design solutions for non-linear load cases

36 Volume Topology Optimization Tetrahedral mesh representing the composite inserts was defined as the design space for this analysis Conducted Volume Topology Optimization on the defined space to optimize the size and location of the proposed inserts Results indicate that this approach provides a reasonable starting point for the design of composite inserts Grey: Design Space Red: Optimal Volume

37 MEARS Conclusions Phase I of the study concluded that multiple solutions achieved the targets established by the FMVSS 216 NPRM. The Phase I team determined that the use of Composite Inserts in conjunction with AHSS and UHSS provided the best design option. Phase II of the project continued the optimization of the final design from Phase I and determined that: A SWR of 3.0 was achievable with a hybrid structure (Steel and Composite Reinforcements) Optimization of the spot weld count can provide benefits to roof strength performance A 4.4 kg mass savings over the donor vehicle body structure was possible while increasing the load carrying capacity by 60% Estimated cost increase of $70 per vehicle Correlation between CAE and physical testing for composite reinforcements has been established Manufacturing Feasibility of Design was confirmed The use of linear optimization early in the development of a program provides insight into the required structural changes

38 Auto/Steel Partnership