关键词: 预裂人字形切槽巴西圆盘, 动态扩展韧度, 动态止裂

Abstract: Recently, much attention has been made on the whole process of dynamic fracture, including crack initiation, propagation and arrest. This study mainly aims to investigate the propagation and arrest of rock under dynamic loading. Experiments were conducted on pre-cracked chevron notched Brazilian disc (P-CCNBD) specimens with a large diameter ( 160 mm) by using split Hopkinson pressure bar (SHPB). Then we determined mode-I dynamic initiation toughness and propagation toughness of marble. Since the employed large-size specimens did not satisfy the stress equilibrium condition in the dynamic test, the papular quasi-static method could not be applied in this study. Hence, an experimental-numerical-analytical method was adopted. The crack initiation time and the crack propagation velocity were monitored by using strain gauges and crack propagation gauges. The recorded experimental data, including dynamic loads applied to the specimens by SHPB, were simulated by 3D finite element analysis program. Then the time history of dynamic stress intensity factor of P-CCNBD was obtained by using the semi-analytical modification with an universal function. The results show that the dynamic initiation toughness of P-CCNBD marble specimen increases with the increase of loading rate. Dynamic propagation toughness of P-CCNBD marble specimen is slightly lower than dynamic initiation toughness. Moreover, dynamic propagation toughness increases with crack propagation velocity. In addition, the oscillation of crack propagation velocity and propagation path deflection were analyzed, and the possibility of achieving crack dynamic arrest in P-CCNBD was discussed as well.

Key words: pre-cracked chevron notched Brazilian disc (P-CCNBD), dynamic crack propagation toughness, dynamic crack arrest