Stress Analysis on an Automotive Crankshaft under Mixed Mode Loading

Abstract

The failures of the crankshafts are constantly subjected to cyclic loading which will tend to display the effects of fatigue that is stochastic in nature. The maximum bending moment occurs during the combustion cycle, where the direction of forces acting on the crankshaft will be exactly towards the centre of the crank radius. The torsional stress occurs during the power cycle can be considered as a quasi-static torsion as it is in steady condition. The aim of this paper is to illustrate the development of the analytical stress analysis used to determine mixed mode loading acting on the crankshaft. The analytical method developed according to the geometric ratio of the connecting rod and crankpin web to determine the variation of bending moment and torsional stress. It was observed that the maximum bending moment and torsional stress acting on the crankshaft are at angles and respectively due to the geometric ratio of the connecting rod and crankpin web. The analytical method that was derived and used for this study provides a good accuracy in determining the critical angles for bending moment and torsional stress acting on the crankshaft based on the geometric ratio.