应力三轴度对船用钢断裂破坏的影响机理分析

Influence of stress triaxiality on fracture characteristics of ship building steel

应力三轴度对船用钢的断裂损伤具有很强的影响。本文通过对典型船用钢Q345B、921A等两种金属材料开展不同应力三轴度下的力学性能试验,利用电镜扫描技术对各试件断裂后的破口进行观察,采用数值仿真手段对试件断裂过程进行模拟,揭示了应力三轴度对船用钢断裂破坏的影响机理。结果表明:(1)试件断裂过程中应力三轴度处于不断变化的过程(剪切试件除外),断裂时刻试件断口位置应力状态分布不一致,结合电镜扫描结果确定了各类试件起始破坏位置;(2)不同应力三轴度下试件断口形态存在较大区别,剪切试件主要形成剪切带而引起破坏,拉伸试件主要由孔洞成长形成韧窝破坏;(3)应力三轴度“断崖现象”与试件类型存在较大关系。本文的研究成果可为后续断裂准则的拟合及材料断裂力学性能试验的开展提供指导。

The stress triaxiality has a strong influence on fracture characteristics of ship building steel.Mechanical experiments of typical Q345B and 921A metal material specimen including different stress triaxiality were performed.Fracture surface of samples were observed by scanning electron microscope(SEM),and numerical simulation method was applied to analyze the fracture process to acquire the variation of typical position stress status.The deep influence of stress triaxiality on fracture characteristics of ship building steel was discussed.The results indicate that:(1)the stress triaxiality changes all the time during damaging process except torsion specimens,and the final distribution is quite different;(2)the fractographs of sample fracture surface are related to stress triaxiality,and torsion specimens are damaged for the reason of shear zone occurring while tension specimens are broken by micro holes gathering;(3)the phenomena of sharp decrease of failure strain in low stress triaxiality region are relevant to specimen variety.The conclusions in this paper could provide assistance for fitting failure criterion and related material failure experiments.