Prediction of fatigue failure in a camshaft using the crack modelling method

Abstract Camshafts made of grey cast iron and used in Rover vehicles were tested under cyclic bending and torsion and modelled using FE. A new technique known as crack modelling was used to predict the fatigue limit. The method uses a linear elastic finite element analysis to derive an equivalent stress intensity factor ( K ) for stress concentrations in components. K is calculated without introducing a crack into the component: the stress field around the maximum stress point is examined and compared to that for a standard centre-cracked plate. This component was a challenge for the technique because it involved a blunt notch and local surface effects. Fatigue limits were successfully predicted for two different designs and two loading modes, but some inaccuracies remain which suggest modifications to the theory.