FATIGUE ANALYSIS ON DIE INSERT OF CONNECTING ROD IN CLOSED DIE FORGING PROCESS

Transcription

1 FATIGUE ANALYSIS ON DIE INSERT OF CONNECTING ROD IN CLOSED DIE FORGING PROCESS By MOHD AMRI BIN SULAIMAN Project Paper submitted to Department of Mechanical and Manufacturing, Faculty of Engineering, University of Putra Malaysia, in partially fulfilment of the requirements for the Degree of Master in Manufacturing System Engineering. May 2006

2 Abstract of the project to the Department of Mechanical and Manufacturing, Faculty of Engineering, University of Putra Malaysia in partially fulfillment of the requirement for the Degree of Master in Manufacturing System Engineering. Abstract: FATIGUE ANALYSIS ON DIE INSERT OF CONNECTING ROD IN CLOSED DIE FORGING PROCESS By MOHD AMRI SULAIMAN Supervisor: Prof. Dr. Abdel Magid Salem Hamouda Faculty: Engineering To meet the increasing demand for more accurate forged products with a higher added value and of higher material yield, precision forging-related technology has been making remarkable progress. In this regard, research and development on CAD/CAM/CAE (computer-aided design/computer-aided manufacturing/computer aided engineering) systems for practical use have been vigorously promoted. CAD/CAM/CAE technology has already established itself in the fields of designing and manufacturing sheet metal dies and is extensively used in the aircraft and automobile industries. The CAD/CAM/CAE system developed and operated for the hot forging of connecting rod.

3 In conventional hot forging of connecting rods, the material wasted to the flash accounts approximately 20-40% of the original workpiece. In order to reduce the cost of forged products, the forging must be performed in a closed cavity to obtain near-net or net shape parts. In flash less forging, the volume distribution of the preform must be accurately controlled to avoid overloading the dies and to fill the cavity. Additionally, the preform must be simple enough to be mass-produced. This work used the CAD/CAM/CAE system for fatigue analysis on die insert of connecting rod in closed die forging process. The implementation of this study consists of five stages; i) modelling part (connecting rod) using CAD software (Solidworks 2005), ii) preliminary die insert design, iii) stress-strain simulation of die insert, iv) die insert fatigue analysis and lifetime, and v) developed CNC code programming for die insert. In the first stage, Solidworks 2005 software was used for modeling part (connecting rod). The second stage, again CAD software (Solidworks 2005) was used to model the primary design of the die insert based on the shape of the forged part. In third stage, simulated the die inserts of connecting rod and analysed the maximum stress-strain applied on the die insert and the requirement of load to perform the forging operation. Meanwhile in fourth stage, determination fatigue analysis and lifetime on die insert was done by comparing the values from S-N curve and maximum stress-strain value from FEA result. In the last stage, Unigraphics software was used to develop CNC machining code or known GM code for fabricating the die inserts. 11

4 Abstrak projek yang dikemukakan kepada Jabatan Mekanikal dan Pembuatan, Fakulti Kejuruteraan, Universiti Putra Malaysia sebagai memenuhi sebahagian dari keperluan untuk Ijazah Sarjana Kejuruteraan Sistem Pembuatan. Abstrak: ANALISIS KELEMAHAN TERHADAP SELITAN ACUAN ROD PENYAMBUNG DALAM PROSES TEMPA ACUAN TERTUTUP Oleh MOHD AMRI SULAIMAN Penyelia: Prof. Dr. Abdel Magid Salem Hamouda Fakulti: Kejuruteraan Bagi memenuhi peningkatan terhadap permintaan kepada barang tempa yang lebih jitu dan berkualiti tinggi, proses teknologi berkaitan kejituan tempaan telah begitu menonjol. Sehubungan dengan itu, pembangunan dan penyelidikan sistem CAD/CAM/CAE untuk tujuan praktikal amat digalakkan. Teknologi CAD/CAM/CAE telah lama diwujudkan terutamanya dalam rekabentuk dan pembuatan acuan kepingan logam dan ia digunakan secara meluas di dalam indusri pembuatan kapal terbang dan kereta. Sistem CAD/CAM/CAB ini juga telah dilaksanakan dan diguna pakai dalam pembikinan rod penyambung. lll

5 Di dalam proses penempaan panas rod penyambung secara normal, pembaziran bahan logam sering berlaku kira-kira peratus daripada bahan logam asal. Oleh itu, untuk mengurangkan kos produk tempaan, proses tempaan mesti dilakukan pada acuan tertutup untuk mendapatkan bentuk yang seakan hampir dari bentuk asal. Di dalam proses tempaan kurang lebihan bahan, jumlah pengaliran logam mestilah dikawal dengan tepat bagi mengelakkan lebihan bebanan kepada acuan. Secara ringkasnya, prabentuk hendaklah sesuai untuk pengeluaran secara besar-besaran. Kajian ini melibatkan penggunaan sistem CAD/CAM/CAE untuk menganalisis kelemahan selitan acuan rod penyambung dalam proses tempa acuan tertutup. Perlaksanaan kajian ini terdiri daripada lima peringkat; i) merekabentuk rod penyambung menggunakan program CAD, (Solidworks 2005), ii) persediaan utama merekabentuk selitan acuan, iii) Simulasi ketegangan selitan acuan, iv) menentukan jangka hayat dan analisis kelemahan selitan acuan, dan v) membangunkan kod program CNC untuk selitan acuan. Pada peringkat pertama, program Solidworks 2005 digunakan untuk merekabentuk rod penyambung. Pada peringkat kedua, sekali lagi program Solidworks 2005 digunakan untuk merekabentuk selitan acuan berdasarkan bentuk rod penyambung. Bagi peringkat ketiga pula, simulasi selitan acuan rod penyambung dan analisis ketegangan maksimum terhadap selitan acuan serta bebanan yang diperlukan untuk proses tempaan ini. Seterusnya peringkat ke empat, menentukan jangka hayat dan analisis kekuatan-kelemahan selitan acuan dengan membuat perbandingan nilai dari graf S-N dan keputusan dari ' finite element analisis' (FEA). Pada peringkat terakhir pula, program Unigraphics digunakan untuk membangunkan kod pemesinan CNC atau dikenali GM-code untuk fabrikasi selitan acuan. lv

6 ACKNOWLEDGEMENT First of all I would like to appreciate to the Kolej Universiti Teknikal Kebangsaan Malaysia, KUTKM as an employer and gave approval to me for furthering my Master study. Also thanks to the Jabatan Perkhidmatan Awam, JPA as sponsorship in this study. Many industry person and academicians from various sources have contributed generously to the completion of this case study. I greatly acknowledge my supervisor Prof. Dr. A. Magid Hamouda, lecturer in the Department of Mechanical and Manufacturing Engineering for his trust, sharing ideas and supportive effort all these while. I would also like to take this opportunity to thank my examiner, Assoc. Prof. Dr. Wong Shaw Voon for his effort and guidance in correcting this case study. I would like to thanks my family, who always has been with me supporting me even in the hardest of time, my dear friends whom have been very helpful and encouraging. This case study is the combination of computer aided design (CAD) for modeling purpose, computer of manufacturing (CAM) for G-code program and fabrication purpose and computer aided engineering (CAE) for finite element analysis purpose. For this I would also like to thank the individual stated below for their time to share information and ideas. Mr. Amir Radzi Engineer Researcher, National CADCAM, Sirim Berhad. Mr. Jefridi Mat Siman Engineer Researcher, Machinery and Tooling Technology Program, Sirim Berhad. v

7 Mr. Goh Kok Ming Production Engineer, Metal Techs Sdn. Bhd, Ayer Keroh, Melaka. Mr. Jaafar Lazim Senior Technician, Faculty of Manufacturing, Kolej Universiti Teknikal Kebangsaan Malaysia. vi

8 APPROVAL This project submitted to the Department of Mechanical and Manufacturing, Faculty of Engineering, University of Putra Malaysia has been accepted as a partial fulfillment of the requirements for the Degree of Master of Manufacturing System. The members of the examinations committee are as below; fa (;2 - -~~ Supervisor, PhD Prof. Dr. A. Magid Hamouda Department of Mechanical and Manufacturing, Faculty of Engineering, University of Putra Malaysia Examiner, PhD Assoc. Prof. Dr. Wong Shaw Voon Department of Mechanical and Manufacturing, Faculty of Engineering, University of Putra Malaysia vii

9 DECLARATION I hereby declare that the project paper is based on my original work except for quotations and citations that have been duly acknowledge. I also declare that it has not been previously or concurrently submitted for any other degree of university or other institutions. MOHD AMRI BIN SULAIMAN viii

10 List of Contents Page ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL SHEETS DECLARATION FORM LIST OF CONTENTS LIST OF FIGURES LIST OF TABLES 111 v Vll V111 IX X111 xv CHAPTER 1 INTRODUCTION Forging for connecting rod Objective Scope of studies Project organizations LITERATURE REVIEW Forging Comparison forging with other processes Why are forging so prevalent Closed die forging Requirements for closed die forging Case Study Flashless Forged Connecting Rod ix

11 Process details Closed-die forging 24 Process requirements 27 Open die forging 29 Hot forging 30 Die life service 30 Die service life based on plastic deformation 31 A brief history of the Finite Element Method 32 The history ofmsc.nastran 33 The overview ofmsc.nastran 35 Connecting Rod in the engine block 37 Basic steps in the finite element method 39 3 METHODOLOGY 40 Stage I: Modelling part using CAD software (Solidworks 2005) 41 Stage 2: Preliminary die insert design 42 Stage 3: Stress-strain simulation of die inserts 43 Stage 4: Die inserts fatigue analysis and lifetime 43 Stage 5: Developed CNC code for the die inserts 43 4 COMPUTER AIDED DESIGN-CAD: Modeling Die Insert 44 Computer Aided Design, (CAD) 44 Solidworks 2005 software for modelling 44 Die insert drawing and dimensions 46 Material properties for die insert 48 Connecting rod drawings, dimensions and material 50 Billet dimensions 52 x

12 5 COMPUTER AIDED ENGINEERING-CAE: Finite Element Analysis on Die Inserts of Closed Die Forging 54 Computer Aided Engineering, (CAE) 54 MSC.NASTRAN software 55 Die Inserts analysis 56 Mesh Element 56 Pressure Load 57 Stress-Strain 58 Displacement on Die Inserts 59 Constraint Force on Die Inserts 59 S-N Curve for Carbon Steels (AISI 1055) 61 Fatigue Analysis of Die Inserts 62 Comparison values between Finite Element Analysis and S-N curve 63 6 COMPUTER AIDED MANUFACTURING-CAM: Die Insert of Closed Die Forging Computer Aided Manufacturing, (CAM) Overview Unigraphics software Tool Path Cavity Mill GM code XI

13 7 RESULTS AND DISCUSSIONS Determination Fatigue Analysis of Die Insert Billet Dimensions CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK The Conclusions of Project 76 Project Contribution System Limitations Recommendations for Future Work REFERENCES 80 APPENDICES Appendix 1: In Part of CNC code for the Machining Operation Required to Produce the Die Insert 82 Appendix 2: A diskette that contain Full CNC code for Die Insert Fabrication 92 BIODATA OF AUTHORS 93 Xll

14 List of Figures Figure 1. Connecting rod 2. Closed die forging with and without flash 3. Closed die forging 4. Comparison between conventional forging and closed die forging 5. Closed die forged connecting rod 6. Stages in forging a connecting rod 7. A heated blank between 2 halves of a die 8. Compressive stroke squeezes the blank into the die 9. Part ejected using an ejector pin 10. Waste material (flash) 11. Connecting rod location in the engine block 12. Forging industry 13. Industrial - Closed Die Forging 14. Flowchart of the methodology 15. Connecting rod 16. Die insert 17. Cavity dimensions (in mm) 18. Cavity depth for Lower Die Insert (in mm) 19. Lower Die Insert dimensions (in mm) 20. Cavity depth for Upper Die Insert (in mm) 21. Upper Die Insert dimensions (in mm) 22. The Upper die insert and lower die insert at open position Page Xlll

15 23. Product (connecting rod) dimensions (in mm) 24. Billet dimensions with offset 2% (in mm) 25. Mesh element on die insert 26. Pressure load applied on the cavity profile 27. Stress-strain 28. Displacement on the die insert (in mm) 29. Constraints force on die inserts 30. Constraints force on bottom die inserts 3 1. S-N curve for carbon steel ( AISI 1055) 32. S-N curve show comparison between O"max and O"se 33. The Create Operation 34. Tool paths for first cavity milling 35. Cavity Mill part 36. Cavity Mill Parameters Setting 37. S-N curve show comparison between O"max and O"se 38. Stress-strain values (in N/m 2 ) for carbon steel AISI 1055 die insert 39. The thickness of billet (in mm) XIV

16 List of Tables Table I. Comparison between forging and welding/fabrication 2. Comparison between forging and casting 3. Comparison between forging and powder metallurgy 4. Comparison between forging and reinforced plastic and composites 5. Comparison between forging and machined steel bar/plate 6. Advantages of forging compare to other process 7. Specifications of the Closed die forged connecting rod 8. AISI Composition of AISI I 055 I 0. Mechanical properties of AISI 1055 Page 9 IO xv

17 Chapter 1 Introduction 1.1 Introduction If the weight of a connecting rod (see Fig. 1) can be reduced while increasing its strength, an automobile's fuel efficiency will be improved. Currently, steel connecting rods are used in passenger cars. However, some manufacturers have attempted to use alternative lighter materials. Recently, various composite materials based on aluminum have been considered, but not yet successfully adopted, for automotive engines. The main reasons are that these materials are not strong enough, or when strong enough, are too expensive. Flash less forging offers the possibility of producing aluminum composite connecting rods at competitive costs. The design of flash less forging processes is more complex than the design of conventional closed die forging with flash. Therefore, in order to accelerate the development of the manufacturing process as well as to reduce the development costs, a new design method must be developed and applied. The finite element method (FEM) offers the possibility to design the entire manufacturing process on a computer. This leads to a reduction of the cost and time in process and tool design, tool manufacturing, and die tryout. In addition, it is possible to modify the process conditions in the simulation to find the best manufacturing conditions for a product. 1

18 Figure 1: Connecting rod 1.2 Forging for connecting rod; In the forging of connecting rods, three main methods are employed. The first method consists of making a rough pre-form from a non-porous billet and hitting it several times in a press until the final shape is obtained (Figure 2a). This method results in 20-40% of the material to be wasted as flash. A major advantage of the closed-die forging with flash is that the volume of the pre-form can vary within a wider range than for flash less forging. This makes it easier to continuously manufacture products with the same quality (3]. However, a trimming process is necessary to remove the existing flash. The second method is net shape flash less forging (Figure 2b). During this process the pre-form is totally enclosed in the die cavity so that no flash formation is allowed. There is no material waste as in impression forging. However, tight volume control of the pre-form is necessary to insure filling of the cavity and to avoid overloading the tooling. The third method, which is widely used, is hot forging of powder metallurgy pre-forms. This method yields virtually no material waste and produces near-net shape products. However, the metal powder is ' expensive compared to conventional materials. 2

19 In principle, forging operations are non-steady state processes, in which the deformation of the material takes place under three-dimensional stress and strain conditions. The material flow depends mainly on the following; I. geometry of the cavity; 2. geometry of the flash opening; 3. initial and intermediate billet geometry; 4. percentage of flash; 5. heat transfer between the tooling and the billet; Forging wi~h Flash Flash less Forging Forging with Flash I I I Fl as hl es~ For~111g Lower Die Start of Stroke I Lower Punch End of Stroke (a) (b) Figure 2: Closed die forging with and without flash Thus, the requirements to perform a successful flashless forging process are: I. The volume of the initial pre-form and the volume of the cavity at the end of the, process must be the same. 2. There must be neither a local volume excess nor a shortage, which means that the mass distribution and positioning of the pre-form must be very exact. 3. If there is a compensation space in the dies, the real cavity must be filled first. 3

20 1.3 Objective of the study Currently most finite element codes that simulate billet-forming processes consider only plane-strain or axisymmetric deformations. Since many industrial parts such as connecting rods have very complex geometries, the metal flow is three-dimensional and cannot be properly modeled with a two-dimensional approximation. This means that a three dimensional simulation of the manufacturing process must be performed to get adequate results. For this study, it is focusing on simulation non-steady process using a finite element method (MSC.NASTRAN) in order to better understanding of structural and fatigue analysis on the closed die forging. The main product to study is connecting rod that most using in automotive industry. Besides, the goals of the study are; );;> To develop a finite element model of die insert for connecting rod in closeddie forging process. );;> To determine fatigue strength material analysis and cycle lifetime of die insert. );;> To developed the CNC code for the die insert using Unigraphics software. 4

21 1.4 Scope of study There are many finite element analysis techniques on closed die forging, for the development of this project, it only concentrated on fatigue strength material analysis of the die insert design using the MSC.NASTRAN software. Meanwhile the Solidworks 2005 and Unigraphic software will be used for modeling and CAM purpose. Currently there have some stages of connecting rod manufacture such as blank, edging, blocking and finishing but in this project, it only highlighted on the final stage (finishing). 1.5 Project organization This project consists of eight chapters: Chapter 1: Introduction of forging for connecting rod, objective and scope of this study. Chapter 2: Reviews on the literature from journal, books and internet. The area covered including types of forging, requirements of closed die forging, process detail of closed die forging, material forged, die life service, history of finite element analysis, history of NASTRAN software and basic steps in the finite element analysis. Chapter 3: Describe methodology in this study to do the modeling, simulation, analysis and developed CNC code. Chapter 4: Modeling the connecting rod and die insert by using CAD software, Solidworks

22 Chapter 5: Finite Element Analysis on Die Inserts of Closed Die Forging, by using finite element software, MSC.NASTRAN. Chapter 6: Developed CNC machining program or known as GM code for die insert fabrication purpose. Chapter 7: Results on of the project and discussions. Chapter 8: Conclusion of the project and recommendations for future works. 6

23 Chapter 2 Literature review 2.1 Forging Forging is defined as the process in which metal is plastically deformed with application of temperature and pressure. It is used to change not only the shape but also the properties of the metal because it refines the grain size and therefore improves its structure [2]. Forging is a cost-effective way to produce net-shape or near-net-shape components. Forged parts are used in high performance, high strength and high reliability applications where tension, stress, load and the human safety are critical considerations. They are also employed in a wide range of demanding environments, including highly corrosive and extreme temperatures and pressures. Various parameters such as complexity of the part, friction between dies and workpiece, type of press, die and workpiece temperature, material of workpiece governs the forging process. Forging process is said to be successful if die cavity is completely filled and stress in the workpiece is less than ultimate stress corresponding to the workpiece material, with minimum force. Forging is the controlled deformation of metal into a specific shape by compressive forces. In year 8000 B.C. forging process are evolved from the manual art of simple blacksmithing. Then a series of compressive hammer blows performs the shaping or forging of the part. Now, modem forging uses machine driven impact hammers or processes, which deform the workpiece by controlled pressure [1]. 7

24 The forging process is superior to casting in that the parts formed have denser microstructures, more defined grains patterns, and less porosity, making such parts much stronger than casting. All metals and alloys are forgeable, but each will have a forgeability rating from high to low or poor. The factors involved are the material's composition, crystal structure and mechanical properties all considered within a temperature range. The wider the temperature range, the higher the forgeability rating. Most forging is done on heated workpieces. Cold forging can occur at room temperatures. The most forgeable materials are aluminum, copper, and magnesium. Lower ratings are applied to the various steels, nickel, and titanium alloys. Hot forging temperatures range from 93 C (200 F) to 1650 C (3000 F) for refractory metals [6]. 2.2 Comparison forging with other processes There are some processes in forming and shaping part such as forging, casting, welded or fabrication, machined steel bar, powder metallurgy, reinforced plastics and composites. All of these processes have their own characteristics, advantages and disadvantages. Here comparison some characteristics such as strength of the part (grain oriented), cost effective, material savings, design flexibility, simplified production, and part inspections, between forging and other process are made. Below Table 1-6 have shown this comparison. 8