Research On The Meso-damage Behavior Of Cold-rolling Silicon Steel Subjected To Low Stress Triaxiality

As the foundational materials in the industries, steel sheet has been widely applied in the fields of civil and military industries. During the rolling process, which is the most important procedure in the production of steel sheet, edge-cracking and the fracture of steel strip have commonly occurred due to the complicated stress state in the edge and result in the adversely influences on the quality of steel strip. Researches on the fracture behaviors of ductile materials were generally concentrated on the high stress triaxiality condition, while systematic researches on low stress triaxiality are needed.Based on the combination of experimental and simulation method, a 3D cell model subjected to low stress triaxiality was studied at present research. The distribution rule of stress and strain was investigated, as well as the developing trend of void and matrix volumes. Further research was carried out to investigate the propagation of voids and material failure under different stress triaxialities especially for low stress triaxiality. By introducing fracture plastic strain as failure criterion, the influence of stress triaxiality and Lode parameter on the damage behavior of ductile materials was inspected via analyzing deformation of voids.Analysis results indicated that there exists complicated distribution of stress and strain near void and void volume fraction decreases as load increases, which showed the traditional models regarding void volume fraction as damage parameter are not appropriate.By introducing fracture plastic strain, a new criterion based on critical equivalence plastic strain was developed to evaluate material damage behavior. And research illustrated that both stress triaxiality and Lode parameter will affect the damage behavior of ductile materials. With the increasing of the stress triaxiality or the Lode parameter, the fracture plastic strain will decrease firstly, and then increase after certain value.The difference is that the influence to the fracture behavior of ductile material of stress triaxiality is more notable than that of Lode parameter.