中文摘要：

冲击载荷作用下准脆性材料的动态断裂一直是关注的热点问题,Ⅱ型裂纹试样受冲击剪切时其裂纹扩展方向同材料力学性质和冲击速度等密切相关。应用岩石动态破裂过程动态分析系统软件,对单边平行双裂缝试样开展了冲击载荷作用下的裂纹动态扩展数值模拟,分别研究了不同材料力学性质、材料均质度、入射应力脉冲幅值和历时对II型裂纹动态扩展的影响。数值模拟结果表明,纯II型裂纹在动荷载作用下的扩展,不仅受到剪切损伤,而且还存在拉伸损伤;准脆性材料的非均匀性导致了主裂缝周围产生大量微裂纹的破坏,影响裂缝的分岔和内部的应力值;应力幅值和应力脉冲历时分别超过某一定值时,主裂缝将出现分叉现象,试样的破坏程度加剧,其研究结果对于深入揭示准脆性材料在动荷载作用下II型裂纹扩展的规律及准脆性材料的损伤断裂机制具有重要的参考价值。

英文摘要：

Dynamic failure of quasi-brittle materials under dynamic loading has been a hot issue; the direction of crack propagation of pre-cracked specimens with mode II crack subjected to impact shear loading is closely related to its mechanical properties and impact velocity. The numerical simulations of dynamic shear crack propagation in specimens with two parallel edge pre-notches subjected to impact loading were carried out to investigate the propagation of mode II crack using rock failure process analysis-dynamic code. The effects of material properties, material heterogeneity, incident stress pulse amplitude and duration on the mode II crack propagation path were also investigated. The numerical results show that the mode II crack propagation under impact loading is induced by the shear damage as well as the tensile damage. Microcracks around main-crack are due to the material heterogeneity, which in turn influences the crack bifurcation and associated stress fields around cracks. Crack branching occurs and the specimen is further damaged when stress amplitude and duration are respectively beyond a certain value. The study result is of great help to investigate the law of mode II crack propagation and reveals the mechanism of damage and fracture of quasi-brittle materials under impact loading.