应用体积元模型汽车零件加工过程边部裂纹分析

Edge Crack Analysis of Automobile Parts Machining Process Based on Volume Element Model

边部裂纹导致的失效在汽车零件加工过程中最容易发生,这将直接影响到车辆的安全与可靠性。针对车身常用的高强钢材料加工过程进行分析,对材料断裂过程进行分析;对比分析不同材料加工间隙与断口光亮带之间关系,分析边部裂纹产生机理,并对断口形貌和组织进行对比分析;基于ABAQUS建立材料内部组织的体积元模型,选取与加工过程组织变化保持一致的单拉工况开展分析;获取在此工况下的应力、塑性应变等的分布情况;对比失效时,模型仿真与试验测试结果的裂纹方向,以验证模拟分析的准确性。分析结果表明:所研究的双相钢材料强度级别高,但由于延展性较差,光亮面所占比率较低,相比于其他材料,冲压成形性较差;裂纹走向呈阶梯状,发生了沿晶断裂与穿晶断裂,裂纹尖端存在微孔洞;单轴拉伸下材料主要以马氏体尖角处产生的微缩孔洞和剪切失效;材料基体组织铁素体的塑性应变加大,并且随着拉伸的进行而增大,表现出明显的加工硬化,与硬相组织间的硬度差缩小,材料的整体应力集中呈现减弱;有限元模拟和试验测试结果的失效过程及最终形貌保持一致,表明有限元模型的准确性,为此类研究提供参考。

The failure caused by edge crack is most likely to occur in the processing of automobile parts,which will directly affect the safety and reliability of vehicles.The processing process of high-strength steel materials commonly used in car body was analyzed,and the material fracture process was analyzed.The relationship between machining gap and fracture bright band of different materials was compared and analyzed,the generation mechanism of edge crack was analyzed,and the fracture morphology and microstructure were compared and analyzed.The volume element model of the internal structure of the material was established based on ABAQUS,and the single tension condition consistent with the change of the structure in the processing process was selected for analysis.The distribution of stress and plastic strain under this working condition was obtained.The crack directions of the model simulation and test results were compared to verify the accuracy of the simulation analysis.The results show that:the strength grade of the dual phase steel is high,but the stamping formability is poor compared with other materials because of its poor ductility and low proportion of bright surface.The crack strike is stepped,intergranular fracture and transgranular fracture occur,and there are micropores at the crack tip.Under uniaxial tension,the material is mainly composed of micro pores and shear failure at the sharp corners of martensite.The plastic strain of ferrite in the material matrix increases and increases with the progress of tensile,showing obvious work hardening,the hardness difference between ferrite and hard phase decreases,and the overall stress concentration of the material decreases;The failure process and final morphology of the finite element simulation and test results are consistent,which shows the accuracy of the finite element model and provides a reference for such research.