Hybrid Topology and Parametric Shape Optimization of Connecting Rod for Weight Reduction and Fatigue Life Enhancement Using FEA

The project titled Hybrid Topology and Parametric Shape Optimization of Connecting Rod for Weight Reduction and Fatigue Life Enhancement using FEA was successfully completed. Three models were designed in SOLIDWORKS and analyzed in ANSYS Workbench using AISI 4340 material. The main conclusions drawn from the results are as follows: 1.                Model 1 is the base design with web thickness 3.0 mm, flange thickness 2.5 mm and solid shank. Its weight is 0.562 Kg. Static analysis gives von-Mises stress 65.38 MPa and deformation 0.0469 mm. Fatigue analysis gives life 1 x 10^15 cycles and safety factor 11.47. Since safety factor is very high and stress is very low compared to yield 750 MPa, it is over-designed and has scope for optimization. 2.                Model 2 is developed by parametric optimization. Web thickness reduced from 3.0 mm to 2.4 mm (20 percent reduction) and flange thickness reduced from 2.5 mm to 2.0 mm (20 percent reduction). Weight reduced to 0.548 Kg with 2.49 percent reduction. Stress increased to 78.06 MPa with 19.4 percent increase. Deformation increased to 0.063 mm. Life remains 1 x 10^15 cycles infinite and safety factor 9.60. Since safety factor still above 2.5 and life infinite, it is safe but not maximum optimized. 3.                Model 3 is developed by hybrid optimization. It retains Model 2 thickness and adds two elongated slots in the web region. Weight reduced to 0.489 Kg with total 12.98 percent approx 13 percent reduction from Model 1. Total material saved 73 grams per connecting rod. Stress increased to 125.87 MPa, deformation increased to 0.0808 mm. This increase is due to reduced cross section and stress concentration at slot fillets. 4.                Even with increased stress 125.87 MPa, it is only 16.78 percent of yield strength 750 MPa, so large margin of safety is available. Deformation 0.0808 mm is less than 0.1 mm and negligible compared to engine clearance. 5.                Fatigue life of Model 3 is 6.18 x 10^13 cycles. Although it is lower than Model 1, it is still greater than 10^6 cycles which is the limit for infinite life. Since all three models have stress below endurance limit 540 MPa, all have infinite life. Therefore Model 3 will never fail due to fatigue under given load. 6.                Safety factor of Model 3 is 5.95 which is lower than Model 1 (11.47) but still 2.38 times higher than required minimum 2.5 for automotive components. Therefore it is optimum utilization of material without over-design. 7.                Damage values for all models are less than 1. Model 1 damage 1e-9, Model 2 damage 1e-9, Model 3 damage 1.618e-5, all safe. 8.                Hybrid optimization proved more effective than only parametric optimization. Parametric gave 2.49 percent weight saving, hybrid gave 13 percent total saving. 9.                The concept of weight-specific fatigue performance enhancement is proved. Absolute life decreased from 1e15 to 6.18e13 but both are infinite. Specific fatigue life per unit weight is improved and reduced weight reduces inertia force F = m _ r _ w^2 which improves actual engine fatigue performance. 10.             Model 3 is selected as final optimum design with maximum weight reduction 13 percent, safe stress 125.87 MPa, infinite life 6.18e13 cycles and safety factor 5.95.

A. Fatemi, J. Williams and F. Montazersadgh, "Fatigue Performance Evaluation of Forged Versus Competing Process Technologies: A Comparative Study," SAE Technical Paper 2002-01-1763, SAE International, 2002.[1] A. Fatemi and S. M. Shenoy, "Dynamic Analysis of Loads and Stresses in Connecting Rod," Journal of Mechanical Design, vol. 127, no. 3, pp. 485-493, 2005.[2] R. Sharma and S. Singh, "Stress Analysis of Connecting Rod with Different Cross Sections Using ANSYS," International Journal of Mechanical Engineering, vol. 6, no. 2, pp. 12-18, 2018.[3] S. Kumar and P. Rao, "Fatigue Life Prediction of AISI 4340 Alloy Steel Under Cyclic Loading," International Journal of Fatigue, vol. 85, pp. 22-29, 2019.[4] V. Gupta and A. Patel, "Topology Optimization of Connecting Rod by Introducing Slots for Weight Reduction," Materials Today: Proceedings, vol. 28, pp. 1450-1455, 2020.[5] A. Verma, K. Singh and N. Yadav, "FEA Methodology for Connecting Rod Using ANSYS Workbench," International Journal of Engineering Research and Technology, vol. 10, no. 5, pp. 234-240, 2021.[6] P. S. Shenoy and A. Fatemi, "Connecting Rod Optimization for Weight and Cost Reduction," SAE Technical Paper 2005-01-0987, SAE International, 2005.[7] S. Kulkarni, R. Desai and M. Patil, "Weight Reduction of Connecting Rod Using Aluminium Alloy and Its Comparison with Steel," International Journal of Automotive Engineering, vol. 7, no. 3, pp. 45-50, 2019.[8] ASM International, "ASM Handbook Volume 1: Properties and Selection: Irons, Steels, and High-Performance Alloys - AISI 4340," ASM International, Ohio, USA, 1990.[9] ANSYS Inc., "ANSYS Workbench User's Guide - Structural Analysis and Fatigue Module," ANSYS 2023 R1 Documentation, Canonsburg, USA, 2023.[10] Dassault Systemes, "SOLIDWORKS 2022 User Guide - Part Modeling and Mass Properties," Dassault Systemes, Waltham, USA, 2022.[11]