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在冲裁有限元模拟中,韧性断裂准则的选择会对冲裁件断面质量与尺寸精度产生很大影响。为了获得符合实际的模拟结果,进而优化冲裁工艺,重点研究了一些常用的韧性断裂判定依据,并从物理学角度阐述了韧性断裂机制。基于试验的韧性断裂准则,考虑了变形历史中的应力应变关系,使用由反求法确定的临界值来判定韧性断裂的发生与否。基于连续损伤力学建立的损伤模型,考虑了变形过程中损伤累积对材料本构关系的影响,能够更准确地描述断裂过程。此外,还分析了冲裁有限元模拟中的关键技术,如采用任意拉格朗日欧拉方法来解决网格畸变问题,使用单元分裂、单元分离与单元删除等技术来处理裂纹的萌发与扩展。探讨了目前韧性断裂模拟中存在问题以及未来发展方向。
In the blanking finite element simulation, the choice of ductile fracture criterion has a great influence on the quality and dimensional accuracy of the cross-section of blanking parts. In order to obtain realistic simulation results and further optimize the blanking process, some commonly used criteria for determining ductile fracture are studied emphatically, and the ductile fracture mechanism is expounded from a physical point of view. Based on the experimental ductile fracture criterion, the stress-strain relationship in the deformation history was considered and the critical value determined by inverse method was used to determine the occurrence of ductile fracture. Based on the damage model established by continuous damage mechanics, the influence of damage accumulation on the constitutive relationship of materials is considered, and the fracture process can be described more accurately. In addition, the key technologies in the finite element simulation of blanking are analyzed. For example, any Lagrange Eulerian method is adopted to solve the problem of grid distortion. The techniques of element splitting, unit splitting and element deletion are applied to deal with the germination and propagation of cracks . The existing problems in the ductile fracture simulation and the future development are discussed.