Distribution of Fatigue Lives for the Diecast Magnesium Alloy

摘要

In this study, fatigue tests were carried out using a diecast Mg alloy AZ91 to study the distribution of fatigue lives under constant stress amplitudes. During the fatigue process of the diecast Mg alloy, cracks initiated from the casting defect within inside of the specimen, and then propagated prior to final failure of the specimen. Distributions of fatigue lives at the constant stress amplitudes can be represented by the Weibull distributions. The scatter in the distribution of fatigue lives becomes larger at the lower stress amplitude of 80 MPa as compared with those at the higher stress amplitudes. There is a common relationship regardless of the stress amplitudes between the initial maximum stress intensity factors K_(imax) and fatigue lives N_f. The lower K_(imax), the longer f becomes. Integrating the fatigue crack propagation law from the initial maximum stress intensity factor K_(imax) to the fatigue fracture toughness K_(fc), the relation K_(imax) vs. N_f can be successfully evaluated.