Fatigue life prediction of cast aluminum alloy based on porosity characteristics

Fatigue life prediction is one of the most important problems in design of industrial components made of defect-containing materials. Not only can defects existing in these materials significantly affect the mechanical properties especially fatigue behavior, but they also lead to considerable scatter in fatigue life. Therefore, a robust design methodology for these materials should consist of statistical evaluation of defects and prediction of fatigue life using an appropriate defect-based model. In this study fatigue life analysis is performed using crack growth models. A small crack growth model is proposed which can consider the effect of mean stress as well as overall plastic deformation. Fatigue life predictions are performed using the defect size measured from the fracture surfaces, as well as the maximum defect size estimated by extreme value statistics within the stressed volume. The predicted fatigue lives based on the proposed model are in very good agreement with the experimental fatigue lives. Discussions of fatigue limit, mean stress, and the effect of defect parameters on fatigue life are also included