Effect of Mean Stress on Fatigue Strength of Non-Combustible Magnesium Alloy

Effect of mean stress on fatigue strength at N=107 of non-combustible magnesium alloy AMX602B(X=Ca) was investigated. Rotating bending fatigue test and tension-compression fatigue test were carried out on specimens with a small hole or crack. It was clarified that the fatigue strength at N=107 of the specimen with the small hole was about 30-150% higher than that of the specimen with the small crack within the range of σm=0~100MPa. This is the reason why the fatigue strength at N=107 of the specimen with the small hole can be not threshold condition for crack propagation but crack initiation. The fatigue strength at N=107 of the specimens with the small hole decreased within the range of σm=100~195MPa due to a static small crack initiating from the small hole at first loading. The effect of mean stress on fatigue strength at N=107 both oh the specimens with the small hole and crack could be estimated using modified Goodman diagram.