中文摘要：

在Valanis的内时本构理论的框架中，引入内结构张量以反映由于非比例加载而引起金属材料的附加等向强化及异向强化效应，同时提出材料强化程度的度量采用沿路径法线方向的塑性应变分量来描述。这些考虑的有效性已经通过用所建模型对304不锈钢材料在一些典型非比例循环加载路径下的响应进行的理论预测得到了验证；将该模型应用于U71Mn材料室温单轴棘轮行为描述中，结果显示内结构张量的引入不仅能较好地反映应变控制下的非比例附加效应，而且也能较好地反映应力控制下塑性应变的累积及变化率。

英文摘要：

Based on Valanis＇ endochronic constitutive equation, a new cyclic plastic constitutive model was proposed to describe the hardening behavior of metallic materials under non-proportional cyclic loadings. In order to describe the additional isotropic hardening and anisotropic hardening due to non-proportional loading, an internal structural tensor related to the geometry of loading path was incorporated into Valanis＇ endochronic constitutive equations. The plastic strain component along the normal of loading path was presented to measure the hardening. The proposed model was verified by simulating the stress responses of 304 stainless steels for a variety of typical non-proportional cyclic loading paths. The predictions have a good agreement with the experimental results in the references. Finally, when the proposed model was applied to simulate the uniaxial ratcheting of U71Mn rail steer at room temperature, a good simulation was obtained. So the introduction of internal structural tensor has advantage of describing not only the additional anisotropic hardening, but also the accumulation of deformation proceeding and rate.