考虑材料失效准则的吸能装置失效行为与碰撞特性

Failure behavior and collision characteristics of energy-absorbing structures considering material failure criteria

在对广义增量应力状态相关损伤模型(GISSMO)失效准则5个基本特性分析的基础上,以DP800为基础材料,从应变场分布、失效单元应力三轴度和应力-应变关系3个方面验证GISSMO失效准则在仿真过程中预测各向同性韧性材料失效的准确性;在此基础上,以挤压式与压溃式2种机车车辆常用吸能装置为研究对象,对比不考虑失效、考虑V-M应变失效准则,考虑GISSMO失效准则条件下,2种吸能装置的失效行为与碰撞特性。研究结果表明:GISSMO失效准则在描述各向同性韧性材料失效行为方面具有较大的优势;吸能装置在轴向碰撞过程中的应力三轴度处于不断变化中,采用考虑应力三轴度的GISSMO失效准则使得仿真结果更准确;针对压溃式吸能装置,在材料断裂应变较小时,采用GISSMO失效准则的仿真计算中结构压溃过程会出现大面积撕裂等失效行为,降低结构的碰撞力和吸能量,在此类吸能装置设计的材料选择中应选择断裂应变较大的材料。

By analyzing the five basic characteristics of the failure criterion of general incremental stress state dependent damage model(GISSMO),DP800 was selected as the basic material,and the accuracy of GISSMO for predicting isotropic ductile material failure behavior during simulation application was verified through three aspects,including strain distribution,the stress triaxiality of failure element and the relationship between stress and strain.Furthermore,the failure behavior and collision characteristics of squeezing and crushing energy-absorbing structures commonly used in the rolling stocks were simulated and compared in conditions of no failure criteria,V-M strain failure criterion and GISSMO failure criterion.The results show that the GISSMO failure criterion has great advantages in describing the failure behavior of isotropic ductile materials.The stress triaxiality of the energy-absorbing structure is constantly changing in the process of axial collision,and the simulation with GISSMO failure criterion,which takes the stress triaxiality into consideration,produces more accurate results.For crushing energy-absorbing structure,when the fracture strain of the material is small,adopting GISSMO failure criterion will cause a large-area failure behavior of the structure and reduction of the collision force and energy absorption.In the design of energy-absorbing structure,a material with a larger fracture strain should be selected.