冲击载荷下含空孔三点弯曲梁的动态断裂行为

为得到圆孔缺陷对运动裂纹扩展过程的影响规律,采用动态焦散线实验方法进行模型实验,研究了冲击载荷下含空孔三点弯曲梁的动态断裂行为。研究结果表明:空孔对裂纹扩展有极大的阻碍作用,在一定范围内,空孔直径越大,阻碍作用越明显。裂纹扩展到空孔附近时,扩展速度会下降。裂纹在空孔上部再次起裂后,最大扩展速度远远大于裂纹与空孔贯通前的最大扩展速度。裂纹扩展至空孔附近时,裂纹尖端动态应力强度因子KdⅠ和KdⅡ均会下降。裂纹在空孔上部再次起裂后,裂尖的应力强度因子KdⅠ和KdⅡ均大于裂纹与空孔贯通前裂尖的KdⅠ和KdⅡ。在整个扩展过程中,裂纹尖端的动态应力强度因子KdⅡ远小于KdⅠ,说明KdⅠ在裂纹扩展过程中起主要作用。

On the Dynamic Fracture Behavior of Three-Point Bending Beam with Empty Hole and Subjected to Impact Loading

In order to understand the influence pattern of circular hole defect on crack propagation process,by using dynamic caustics method,a model experiment was carried out to study the dynamic fracture behavior of three-point bending beam with empty hole.Experimental results indicate that empty hole has a significant impediment effect on crack propagation.In a certain range,the larger the empty hole diameter is,the more obvious the impediment.When a crack extends to the vicinity of an empty hole,its propagation rate decreases.When the crack appears again in the upper part of the empty hole,its maximum expansion velocity is much larger than that before the crack and the empty hole coalescence.When a crack extends to the vicinity of an empty hole,both dynamic stress intensity factors at crack tip KdⅡ and KdⅡ decrease.When the crack appears again in the upper part of the empty hole,both dynamic stress intensity factors at crack tip KdⅠ and KdⅡ are larger than that before the crack and the empty hole coalescence.In whole crack propagation process,the dynamic stress intensity factor KdⅠ is always less than KdⅡ,which indicates that KdⅠ plays a main role in crack propagation process.