A Durability Prediction for the Magnesium Alloy AZ31 based on Plastic and Total Energy

Magnesium has a good strength-to-weight ratio. As a result, magnesium alloys are gradually becoming an integral part of lightweight designs that are especially important to the automotive and aerospace industries. The magnesium alloy AZ31 is particularly suitable for forming. Furthermore, as its cyclic response is asymmetric, the accumulated energy during loading is a convenient basis for durability predictions of a product that is made of the AZ31 alloy. In this article, we show how the inverse-power law model can be combined with a Weibull's probability density function to describe the shape of the fatigue-life curves and their scatter. Various load histories were chosen to characterize the response of the AZ31 alloy under different cyclic loadings. Both the plastic and the total strain energy densities were calculated for all the load histories, and then, a suitable dependence in terms of energy fatigue-life curves was determined. The proposed model is appropriate for modeling the low-cycle fatigue life of the AZ31 alloy. With the application of a linear damage-accumulation rule, it is also possible to predict the fatigue life for the non-constant amplitude loading within one decade of accuracy.