Basic research on impact design method without material properties considering strain rate dependence

Finite element method based numerical simulation (CAE) came to be utilized in the strength design by the development of the design technology. In particular, it is very important to use CAE when evaluating the safety of products subjected to impact loads. This is because the Product testing with impact load is difficult and expensive to perform. However, there are two major problems with this CAE. The first problem is the high cost of installing and maintaining CAE software. The second problem is that only some of the materials implemented with CAE have material properties that take into account the strain rate dependence needed to assess material fracture. Ductile fracture prediction formulas for evaluating material failure are implemented in many CAE software. However, in order to use the ductile fracture prediction formula, material properties that take strain rate dependence into consideration are required. In this study, we examined a design method based on an energy of fracture of materials and input energy of impact phenomenon by using experiments and numerical simulations without using material properties considering strain rate dependence. In this research, static three-point bending test, Charpy impact test and elasto-plastic analysis were performed to confirm the validity of the proposed design method. Firstly, In the three-point bending test, the amount of energy input to the test pieces was examined. Secondly, in the Charpy impact test, the same energy as the static three-point bending test was input to the test pieces. Thirdly, the elasto-plastic analysis used material properties that did not take into account the strain rate dependence obtained from static tensile tests. Finally, these results were compared. As results of comparison, it is clear to the efficacy of the proposed impact strength design method.