Influence Of Stress-State On Material Damage-Experimental And Numerical Investigation

In this thesis, the tension failure experiments taken 15 kinds of pure aluminum specimen and 12 kinds of pure copper specimen with different thickness and different center round hole were carried out. The entire experimental processes of all specimens were recorded for the tensile deformation, the hole changing in shape and the final rupture. Then the fracture strain that was affected by specimen's thickness (stress triaxiahties) and other influencing factors for the two materials were analyzed.On the basis of experiments, the elastic-plastic large strain FEM numerical calculations were performed for the 15 kinds of pure aluminum specimen and the 12 kinds of pure copper specimen with different thickness and different diameter of center round hole. The experimental processes under tension loading for all specimens were simulated by this method, and the results were compared with the experimental records in different respects.Further the influences of stress-state on material's rupture were investigated by numerical simulation associated with experimental analysis. The mechanical parameters such as "combinatorial work density", "ratio of void growth", "stress triaxialities" and "Lode parameter" were calculated and analyzed for the specimens under tension. According to the numerical results of specimen's ligament and comparisons, the parameter's variations for specimen with different thickness and with different diameter of center hole were investigated, and the mathematical descriptions for different two rupture criterion were given out.The work of this thesis find the previous conclusion from Gurson model and GTN model that the fracture strain will decrease with stress triaxialities rising is not always true.