On the distributions of fatigue lives and defect-sizes in the die-cast magnesium alloy AZ91

Abstract

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 existing inside of the specimen, and then propagated prior to final failure of the specimen. The probabilistic distributions of the defects densities, of the defect sizes, and of the spatial positions of the defects were investigated experimentally in detail. The distributions of the fatigue lives of the diecast Mg alloys under the constant stress amplitudes were evaluated using the Monte-Carlo simulation, in which the random numbers corresponding to the above probabilistic distributions for the casting defects are used. There was a good fit between the evaluated distribution of the fatigue lives by the computer simulation and the experimental one. An increase of scatter in the distribution of the fatigue life with lowering of the stress amplitude could also be predicted using the simulation.