A through process model of the impact of in-service loading, residual stress, and microstructure on the final fatigue life of an A356 automotive wheel

Fatigue life is a key consideration in the design of cast aluminium alloy automotive wheels. In this investigation, a through process modelling methodology was used to predict the fatigue life of an A356 automotive wheel subject to bending fatigue. This methodology considers the evolution of microstructural features and stress state through the manufacturing process (including casting, heat treatment, and machining) and during service loading. This paper focuses on validating the in-service model and quantifying the interaction between the key factors influencing fatigue behaviour. The cyclic elastic strains measured on the wheel surface for a series of different bending loads were found to agree well with predictions. The predicted crack initiation sites and the number of cycles to cause failure in the wheel were in agreement with full scale fatigue tests on wheels. The fatigue life and associated scatter are shown to be a function of microstructure, residual stress and in-service loading. Both the pore size and loading level have a significant impact on fatigue behaviour, while residual stresses showed a moderate influence on fatigue life for the wheel.