爆炸应力波作用下分支裂纹动态力学特性试验

Experimental study of dynamic fracture behaviors of branched cracks under blasting stress wave

应用爆炸加载的透射式动焦散线测试系统,分析了平板中预制贯通裂纹在爆炸应力波作用下端部衍生分支裂纹及爆炸主裂纹的扩展规律。预制贯通裂纹面在压缩应力波及反射拉伸波作用下表现出明显的张开和闭合交替变化,预制贯通裂纹减弱了爆炸主裂纹的动态扩展行为,爆炸主裂纹难以穿过预制贯通裂纹继续扩展。分支裂纹是爆炸应力波在预制贯通裂纹端部衍射效应形成应力集中而衍生、起裂、扩展,其开裂角与预制贯通裂纹、爆炸应力波入射角密切相关,分支裂纹尖端沿着最大能量释放率方向起裂,逐渐平行于最大主应力的方向稳定扩展,中后期扩展多表现为复合型断裂。爆炸分支裂纹的动态应力强度因子、扩展速度低于爆炸主裂纹,获得了分支裂纹起裂韧度为0.50～0.65 MN/m3/2、止裂韧度为0.25～0.35 MN/m3/2。

Dynamic caustics experimental technique is used to study dynamic characteristics of the propagation of explosion main cracks and branched cracks under blasting stress wave.The prefabricated cracks were opening or closing as a result of the explosion stress wave reflection from these cracks,and reduced the dynamic behaviors of explosion main cracks.These main cracks can＇t generally pass through the prefabricated cracks and continue to extend.The branched cracks are derived from the ends of the prefabricated cracks.The initiation and propagation of branched cracks are caused by the diffraction effective of tensile stress concentration of the prefabricated crack tips.The split angles of branched cracks are closely related to the prefabricated cracks and angle of blasting incidence stress wave.The branched cracks initiation is started from the direction of generalized maximum energy release rate,and shown as mixed mode fracture and the stability propagation with the direction of maximum principal stress.The dynamic stress intensity factor and velocity of branched cracks are lower than blasting main cracks＇.The initial fracture toughness of branched cracks is about 0.5-0.65 MN/m3/2.The arrest toughness of branched cracks is about 0.25-0.35 MN/m3/2.