A study of fatigue failure initiation in high cycle high-pressure automotive applications and conventional rotating bending fatigue testing

The search for greater power and efficiency from automotive engines places components under ever increasing stress. This study compares results obtained from testing of engine components under extreme operating conditions with those obtained from laboratory-based tests. Conventional rotating bending fatigue testing has been applied to high strength alloy steel samples processed and heat treated under the same conditions as engine test components. The results are compared with those obtained from engine components tested under high-pressure cyclic loading using specially designed engine test rigs. Failure initiation sites in the high strength alloy steel samples have been identified and categorised using scanning electron microscopy with X-ray mapping. The influence of inclusion content, heat treatment process and surface finish have been determined and used to inform design considerations, heat treatment processing conditions and material selection.