讨论:材料非线性分析中各种硬化准则下屈服应力的输入(已搜索无重复)

pla_yong

最近在做材料非线性方面的项目,有一些关于材料本构关系中屈服应力的疑问想和大家讨论一下.刚才搜索了关于屈服应力以往的帖子,大多是关于得出的屈服应力比输入的要大方面的问题.
我的疑问是在各种不同的硬化准则下,比如MISO和MKIN硬化准则下,材料本构方程是通过应力应变关系曲线定义的,那么程序是怎么确定材料的屈服应力的呢?难道是把最后一个输入的应力值作为屈服应力?我觉得好象不是这样的,希望大家能够提示.谢谢!

zhang617725

我的理解是由于MISO材料模型不需定义屈服应力，所以程序是不需要确定屈服应力来求解的，而是根据定义的应力应变关系曲线

pla_yong

不对呀,塑性理论中关键一点就是判断何时发生屈服,屈服准则不就是这个作用吗?

tonnyw

1# pla_yong

Here you are talking about two types of hardening rules: Isotropic hardening(MISO) and Kinematic hardening(MKIN).

For isotropic hardening, it means the center of the yield surface is fixed and the yield surface keeps expanding. The yield function is defined as f =1/2*S^T*S - yield_stress^2/3 where S is deviatoric stresses. The yield stress is determined from the input multilinear stress-strain curve generated from unaxial test.

For kinematic hardening, it means the yield surface is fixed and the center of the yield surface keeps moving. The yield function is defined as f =1/2*(S-alpha)^T*(S-alpha) - initial_yield stress^2/3 where alpha is the translation of the yield surface. Here the yield stress is called initial yield stress which means the first point in the input stress-strain curve.

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pla_yong

谢谢你的回答，我还有一个疑问，你的回答中在MISO硬化准则中，屈服应力是根据单轴实验得出的应力应变曲线决定的。具体是根据什么原则决定的呢？是不是输入的应力应变曲线上的第一个点也代表初始屈服应力呢？请你看到后给我发个信息解答一下，非常感谢你的帮助！