A Kinematic Hardening Constitutive Model For The Cyclic Plastic Response Of Magnesium Sheet Alloys At Room Temperature

Great attention has been paid to the magnesium alloy because of its excellent mechanical properties.It has great application prospects in the fields of transportation,aerospace and electrical engineering.However,due to its own unique hexagonal closed packed(HCP)crystal structure and the strong initial basal texture caused by forming,its mechanical behavior under both monotonic and cyclic loading is very complicated,which is quite different from common metals.The lack of a simple and computationally efficient numerical model to simulate the mechanical response of the magnesium alloy under cyclic loading has impeded the further application of magnesium alloy to the industry.Therefore,that understanding the plastic deformation mechanism of magnesium alloy,studying its plastic deformation characteristics,and then putting forward a simple and effective cyclic plastic constitutive model is very important for improving the utilization of the magnesium alloy in the world.Based on the CPB06 yield criterion which is anisotropic and asymmetric between both tensile and compressive yield strengths,a cyclic plastic constitutive model based on a kinematic hardening law is established.By introducing the evolutional equations of back stresses under different deformation modes,such as slip,twinning and untwinning,the abnormal cyclic hardening behavior of magnesium alloy sheet at room temperature was simulated.The experimental results of two kinds of magnesium alloy sheets—AZ31B-O and AZ31 B were adopted in this work.The parameters of the model were determined by some experimental curves under different loading paths such as tension-compression-tension(T-C-T)and compression-tension(C-T).A Cubic interpolation polynomial was employed as a function between the back stress parameters and the equivalent plastic strain accumulated in the previous deformation mode(ie,plastic prestrain).The constitutive model proposed in this work was used to predict the remained experimental curves.The predicted results showed good agreement with the corresponding experimental results,indicating the correctness of the current model.