Determination of the Relationship between Proportional and Non-Proportional Fatigue Damage in Magnesium Alloy AZ31 BF

In this work, the magnesium alloy AZ31BF subjected to proportional and non-proportional loads has been studied. For this purpose, a series of experimental multiaxial fatigue tests were carried out according to the ASTM E466 protocol. The main objective was to determine the relationship between the multiaxial fatigue strength of this alloy under these two different types of loading. The results showed that the AZ31BF magnesium alloy has different fatigue strengths depending on the loading type. Based on these results, it was found that the ratio between proportional and non-proportional damage in AZ31BF magnesium alloy varies depending on the number of loading cycles. To represent this variation, parameter Y was used to modulate the non-proportional damage of AZ31BF. In this way, two Y functions were considered, one for the normal stress component and the other for the shear stress component. The results obtained for the non-proportional parameter Y are of particular interest since the multiaxial fatigue models do not distinguish between these two types of loading when evaluating fatigue life. In this sense, the results of this study can be used in these models to overcome this limitation.