Parameters calibration of nonlinear isotropic/kinematic hardening model for magnesium alloy under cyclic loadings

Magnesium alloys have been widely used as lightweight materials in the field of engineering components. That is because of their favorable combination of the tensilestrength (160 to 365 MPa), the elastic modulus (45 GPa), and the low density (1740 kg/m3). Thus, investigating mechanical and fatigue properties ofmagnesium alloys is important to use in industries. In this article, results of experimental fatigue tests areused to calibrate the parameters of the nonlinearisotropic/kinematic hardening model for a magnesium alloy (AZ91). This model is mostly applied to anumerical analysis to predict the cyclic stress-strain loop and the elastic-plastic behavior of materials. The non-linear kinematic hardening component describesthe Bauschinger effect by explaining the translation of the yield surface in the stress space through the back stress. This law is defined as a supplement combinationof a linear term and a relaxation term, which presents the non-linearity. The material constants of this modelare found by thermo-mechanical fatigue tests and also, low cycle fatigue tests at different temperatures for the AZ91 alloy. Then, the results of the elastic-plasticbehavior of the AZ91 alloy are compared to the experimental results. The maximum relative error of stress values which are obtained by the proposednumerical approach is 20% under low cycle fatigue loadings and the accuracy of the model is better under thermo-mechanical fatigue loadings.