基于新弹塑性模型全程模拟金属疲劳失效

金属材料疲劳失效问题是工程中一类主要问题，选择合理的材料本构关系对于准确确定疲劳失效强度至关重要．本文提出一个简单形式的自由光滑新弹塑性模型，该模型在不涉及通常的屈服条件以及加卸载条件的意义上完全自由，避免了模量间断问题，且比经典模型更简单、更符合实际．结果表明，该模型可直接模拟金属材料在循环加载下直至疲劳破坏的全过程，不涉及任何损伤变量以及人为假设的失效判据，特别地，可直接模拟金属材料的高周、低周疲劳直至最终失效破坏行为．应用P92钢的相关实验数据，给出了循环加载下的数值模拟结果，结果表明，在各种加载-卸载循环情形下，随着应力幅值的增大，疲劳失效循环数减少，这与实际材料行为相一致．

Direct Simulation of Metal Fatigue Failure Based on New Elastoplastic Model

The fatigue failure of metal materials is one of the main problems in engineering. It is very important to choose a reasonable material constitutive relation for the accurate determination of fatigue failure strength. In this paper, a new elastoplasticity model for metals is put forward. This model is free and smooth in the sense of bypassing the usual yield criterion and loading-unloading conditions, and is simpler and more realistic than usual models. It is demonstrated that metal fatigue behavior within the whole deformation range up to failure can be simulated directly by this model, without involving any damage-like variables as well as any ad hoc criteria for failure. In particular, both the high cycle and low cycle fatigue of metal materials can be directly simulated up to the final failure. Numerical examples are presented for P92 steel. The results show that under various loading and unloading conditions, the number of fatigue cycles before failure decreases with of the increase of stress amplitude, which is in general agreement with the realistic behavior of metals.