基于LS-DYNA的热成型钢断裂失效预测研究

Failure Prediction of Hot-formed Steel Based on LS-DYNA

热成型钢在汽车行业的普遍应用,为汽车轻量化及燃油经济性带来显著提升.然而热成型钢特殊的淬火硬化工艺又使得其塑性延展性显著降低.因此在整车碰撞等大变形情况下,热成型钢断裂失效的准确模拟、预测显得尤为重要.论文以宝钢B1500HS热成型钢为研究对象,通过完善的材料力学实验,获得了LS-DYNA＊MATADDEROSION模块中Damage initiation and evolution criteria（DIEC）失效模型的各个参数,并通过设计热成型B柱子系统试验对该失效模型进行验证.结果表明DIEC失效模型可以准确预测热成型钢的断裂失效行为.该研究可对早期开发阶段的车身热成型结构优化设计提供参考.

The widespread use of hot-formed steel in automobile industry greatly reduces weight of vehicles and enhances fuel economy.However,the ductility of hot-formed steel is significantly reduced because of the special quench hardening process,which easily leads to fracture failure and structural instability.Therefore,it is essential to learn and exactly predict the fracture failure of hot-formed steel,especially in the case of large deformation such as the high-speed crash situation.In this paper,the approach to predicting the fracture failure behavior of hot-formed steel（B1500 HS from Baosteel）is studied.A series of material experiments are carried out first to represent the failure properties of B1500 HS under different stress states.After that,the failure model called Damage Initiation and Evolution Criteria（DIEC）in LSDYNA code is employed to simulate the failure behavior of B1500 HS.The DIEC model includes several failure mechanisms,such as the ductile normal fracture caused by initiation,growth and coalescence of voids,shear fracture caused by shear band localization and instability with localized necking.The fracture limit curves,which are important inputs for the DIEC model,are fitted based on the material experimental data.It should be clarified that the elasto-plastic properties of B1500 HS are modeled using the classic LSDYNA MAT24.The effectiveness of this approach in failure prediction is finally discussed by comparing the numerical results with those of a three-point bending test based on the hot-formed B post.It is shown that the DIEC model can predict the fracture failure behavior of hot-formed steel correctly.The fracture position,failure mode and force-displacement curve obtained from the simulation are all consistent with those from the test.This study may provide a good reference for the optimized design of hot-formed car body components in early stage.Moreover,the approach presented in this paper is general and can be extended to other metals such as high strength steel,mild steel,aluminum,etc.for fracture failure prediction.