Stress Analysis and Optimization of Crankshafts Subject to Dynamic Load
Gaurav Yadav1, Sanjeev Kumar2

1Sanjeev Kumar, Assistant Department of Professor Mechanical Subharti Institute of Technology and Engineering Swami Vivekanand Subharti University, Meerut, (U.P), India.
2Gaurav Yadav, Department of Mechanical, Subharti Institute of Technology & Engineering Swami Vivekanand Subharti University, Meerut, (U.P), India.
Manuscript received on 20 July 2014 | Revised Manuscript received on 25 July 2014 | Manuscript published on 30 July 2014 | PP: 7-9 | Volume-3 Issue-3, July 2014 | Retrieval Number: B1101053214/2014©BEIESP
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Abstract: Stress Analysis and Optimization of Crankshafts Subject to Dynamic Loading The main objective of this study was to investigate weight and cost reduction opportunities for a forged steel crankshaft. The need of load history in the FEM analysis necessitates performing a detailed dynamic load analysis. Therefore, this study consists of three major sections: (1) dynamic load analysis, (2) FEM and stress analysis, (3) optimization for weight and cost reduction. In this study a dynamic simulation was conducted on two crankshafts, cast iron and forged steel, from similar single cylinder four stroke engines. Finite element analysis was performed to obtain the variation of stress magnitude at critical locations. The pressure-volume diagram was used to calculate the load boundary condition in dynamic simulation model, and other simulation inputs were taken from the engine specification chart. The dynamic analysis was done analytically and was verified by simulations in ADAMS which resulted in the load spectrum applied to crankpin bearing. This load was then applied to the FE model in ABAQUS, and boundary conditions were applied according to the engine mounting conditions. The analysis was done for different engine speeds and as a result, critical engine speed and critical region on the crankshafts were obtained. Stress variation over the engine cycle and the effect of torsional load in the analysis were investigated. Results from FE analysis were verified by strain gages attached to several locations on the forged steel crankshaft. Results achieved from aforementioned analysis were used in optimization of the forged steel crankshaft. Geometry, material, and manufacturing processes were optimized considering different constraints, manufacturing feasibility, and cost. The optimization process included geometry changes compatible with the current engine, fillet rolling, and the use of microalloyed steel, resulting in 18% weight reduction, increased fatigue strength and reduced cost of the crankshaft, without changing connecting rod and/or engine block. A 26% weight reduction is also possible considering changes in the main bearings and the engine block.
Keywords: FEM, ABAQUS,  ADAMS, FE.

Scope of the Article: Predictive Analysis