定向断裂双孔爆破含缺陷介质裂纹扩展的动焦散试验

利用爆炸加载数字激光动态焦散线试验系统,进行双孔爆破爆炸应力波作用下缺陷介质裂纹扩展试验。研究了含水平预制裂纹和竖直预制裂纹的介质裂纹扩展路径、速度、加速度和裂尖动态应力强度因子变化规律。试验结果表明:在爆炸应力波作用下,预制裂纹尖端起裂,并扩展。炸药爆炸后,主裂纹的扩展速度迅速达到峰值,之后开始振荡减小,其加速度呈现波浪起伏式的振荡变化。次裂纹起裂后速度增大至峰值,然后开始减小。主裂纹尖端的动态应力强度因子K_Ⅰ从峰值振荡减小,又振荡增加至第二个峰值,之后振荡减小。次裂纹尖端的动态应力强度因子K_Ⅰ达到最大时,次裂纹起裂,之后K_Ⅰ振荡减小。裂纹扩展的过程中K_Ⅱ基本都小于K_Ⅰ。

Dynamic Caustics Experiment on Crack Propagation in Defective Medium by Directional Breaking with Double Hole Blasting

The experimental system of explosive load digital laser dynamic caustics was used to study the propa-gation behavior of cracks under the effect of explosive stress waves of double holes explosion.Meanwhile,the path, velocity and acceleration of the propagation of cracks in a Polymethyl methacrylate(PMMA)medium were also stud-ied,including horizontal and vertical prefabricated cracks and the variation of dynamic stress intensity factor at the tip of the cracks.The experimental results show that the tip of the prefabricated cracks propagated under the effect of an explosive stress wave.After detonation,the velocity of the main crack rapidly peaked,then decreased in oscillation. After the secondary crack,its velocity peaked and then began to decrease.The dynamic stress intensity factor KⅠat the main crack's tip decreased from the peak value in oscillation,and increased to the second peak value,then de-crease in oscillation.When the dynamic stress intensity factor KⅠat the main crack's tip reached the maximum val-ue,the secondary crack initiated,and then KⅠdecreased in oscillation.In the process of crack propagation,the KⅡwas almost less than KⅠ.