含不同张开角度裂纹结构的动态断裂实验研究

Open crack is quite common in engineering structures, while its open angle is usually uncertain. The existence of crack defects has a significant effect on the dynamic fracture behavior of structures. To study the interaction between the running crack and the prefabricated crack with different open angles, the open angle was set as a single variable in the experiments. A dynamic caustics experiment system was used to conduct the three-point bending experiments on PMMA specimens under impact load. The results show that: when the crack propagates through the prefabricated crack, it always propagates first to one of the ends of the prefabricated crack, then propagates from the end toward the drop hammer point, and finally penetrates through the whole specimen; the prefabricated crack with upward opencrack will increase the propagation time of the running crack, the larger the open angle of the prefabricated crack, the larger the hysteresis effect on the crack propagation, and the longer the total duration of the crack penetration; during the period of interaction with the prefabricated crack, the dynamic crack propagation velocityfirstly slows down and then increases to the peak, the larger the prefabricated crackangle, the smaller the peak of crack propagation velocity, meanwhile, the peak value of the specimen withl80° open crack is very close to that of the specimen without prefabricated crack; when the running crack initiates again from the end of the prefabricated crack, the stress intensity factor at the crack tip increases rapidly and then decreases rapidly until the specimen completely breaks.