中文摘要：

为检验Chaboche率相关本构模型对材料屈服与塑性流动行为的描述能力，编写了ABAQUS材料用户子程序UMAT，结合预拉伸变形后的45号钢拉扭组合试验，用Chaboche粘塑性模型进行了宏观尺度的材料屈服特性和塑性流动规律的数值分析。该模型可以准确的描述材料不同应变幅值的试验循环滞回特性；当用较大平移应变定义屈服时，试验和数值模拟得到的后继屈服面形状均接近于圆；用较小平移应变定义屈服时，Chaboche模型计算的屈服面与试验得到的后继屈服面形状差异较大。模拟计算的塑性流动方向符合正交流动法则，而试验测得的塑性流动方向和正交方向存在一定偏差，定义屈服的平移应变越小，两者偏差越大。研究结果表明：Chaboche塑性本构模型能够描述较大平移应变定义的屈服面的膨胀和移动，但不能描述小平移应变定义的屈服面的形状变化。

英文摘要：

In order to verify the description ability of Chaboche rate-dependent model on the yielding and plastic flow, a user-defined material （UMAT） subroutine for ABAQUS is developed. Comparing with the tension-torsion experiment of a 45 steel after pre-tension, yield surfaces and plastic flow directions are calculated by simulation using FEM associated with the model. The numerical results verify that the model can be applied to describe the hysteresis tested under the cyclic loading with different strain amplitude, Based on the larger offset strain definition, the subsequent yield surfaces are close to a column surface. Whereas using the yield definition with a smaller offset strain, the shape distortion of subsequent yield surface becomes more prominent. For the conventional plastic theory based on Drucker＇s postulate, the plastic flow directions on yield surface are in agreement with the normality rules. But the experimental results are found having larger deviation from the normal di- rections. The smaller the offset strain for yield definition, the larger deviation between the normal directions and the plastic flow directions will have. The results reveal that the Chaboche model can reasonably describe the translation and expansion of yield surface strain, and not fit to describe the distortion evolution of yield offset strain. if it is determined surface determined by a larger offset by a fairly small offset strain.