Fatigue Life Prediction of Leaf Spring through Multi Mean S-N Approach

Abstract

Parabolic leaf spring is a suspension component for heavy vehicles where spring itself experiences repeated cyclic loading under operating condition. Fatigue life of the parabolic leaf spring is vital since the deflection of the spring is large and continuous. To determine the fatigue life of the parabolic leaf spring, material properties input to the design is important. The objective of this study is to predict the fatigue life of a parabolic leaf spring based on two different material grades which are SAE 5160 and SAE 51B60H under constant amplitude loading through various mean stress method. SAE 51B60H is the material with slightly higher carbon, manganese and chromium content compared to material SAE 5160. Chemical composition differences between SAE 5160 and SAE 51B60H have significant effects on the mechanical properties and fatigue life. In this analysis, finite element method together with multi mean curve stress life (S-N) approach has been implemented to estimate the fatigue life of the spring. Goodman, Gerber and Interpolate mean stress correction method were adopted to correct the damage calculation for mean stress. The results show that interpolate and Goodman method predict the fatigue life of the material with higher accuracy. On the other hand, material SAE 51B60H yields higher fatigue life compared to material SAE 5160.