Jung Jae-Wook, Lee Sang Eon, Hong Jung-Wuk
Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea.
Materials (Basel). 2019 Aug 26;12(17):2736. doi: 10.3390/ma12172736.
Simulation of the material failure under high strain rate conditions is one of the most difficult problems in the finite element analyses, and many researchers have tried to understand and reproduce dynamic material fracture. In this study, we investigate a failure criterion that minimizes the mesh dependency at high strain rates and incorporates the criterion into the Johnson-Cook constitutive relationship by developing a user-defined material model. Impact tests were performed using a gas-gun system in order to investigate the response of the 7075-T651 aluminum plate in high-speed collision. On the other hand, numerical simulations are carried out by considering various element sizes and the relationship between element size and failure strain is inversely obtained using numerical results. By accommodating the relationship into the damage model and implementing in the user-defined material model, mesh dependency is significantly reduced, and sufficient accuracy is achieved with alleviated computational cost than the existing damage model. This study suggests an element size-dependent damage criterion that is applicable for impact simulation and it is expected that the criterion is useful to obtain accurate impact responses with a small computational cost.
在高应变率条件下模拟材料失效是有限元分析中最困难的问题之一，许多研究人员试图理解和再现动态材料断裂。在本研究中，我们研究了一种在高应变率下使网格依赖性最小化的失效准则，并通过开发用户定义材料模型将该准则纳入约翰逊-库克本构关系。为了研究7075-T651铝板在高速碰撞中的响应，使用气枪系统进行了冲击试验。另一方面，通过考虑各种单元尺寸进行数值模拟，并利用数值结果反求单元尺寸与失效应变之间的关系。通过将这种关系纳入损伤模型并在用户定义材料模型中实现，显著降低了网格依赖性，与现有损伤模型相比，在降低计算成本的同时实现了足够的精度。本研究提出了一种适用于冲击模拟的与单元尺寸相关的损伤准则，预计该准则有助于以较小的计算成本获得准确的冲击响应。
