室温下镁合金板循环塑性随动强化本构模型研究

Investigation on the Kinematic Hardening Constitutive Model for the Cyclic Stress-Strain Response of Magnesium Sheet Alloys at Room Temperature

本文在具有各向异性屈服强度和拉压不对称的CPB06屈服准则的基础上,建立了基于随动强化的循环塑性本构模型.通过引入滑移、孪晶以及去孪等不同变形模式下的背应力演化方程,对室温下镁合金板材异常循环硬化行为进行了模拟.选取了AZ31B-O和AZ31B两种镁合金板材,通过拉伸-压缩-拉伸(T-C-T)和压缩-拉伸(C-T)等不同加载路径下的部分实验曲线确定模型的参数,采用三次插值多项式建立了背应力参数与上一变形模式中累积的等效塑性应变(即预应变)之间的函数关系.使用本模型对剩下的实验曲线进行了预测,发现预测结果与实验结果有良好的一致性,说明了当前模型的正确性.

A kinematic hardening constitutive model is presented, in which a simplified CPB06 yield criterion is adopted, and the asymmetry in the initial tension and compression yield stresses of magnesium （Mg） alloys at room temperature （RT） is considered. The hardening behavior was classified into slip, twinning, and untwinning deformation modes, which were described by two forms of back stresses to capture the mechanical response of Mg sheet alloys under cyclic loading tests at RT. Experimental data were obtained for AZ31B-O and AZ31B sheet alloys under both tension-compression-tension （T-C-T） and compression-tension （C-T） loadings to calibrate the parameters of back stresses in the proposed model. The predicted parameters of back stresses in the twinning and untwinning modes were expressed as a cubic polynomial. The predicted curves based on these parameters showed good agreement with the test results.