冲击载荷作用下材料I型动态断裂行为研究

利用焦散线实验对含预制裂纹半圆盘试件在落锤冲击载荷作用下的断裂行为进行了研究,采用实验-解析法测定了试件受到的落锤冲击载荷的变化情况。实验结果表明：在裂纹起裂前,作用于试件上的冲击力总体表现为不断增大的趋势；当试件受到的冲击力达到最大值4.8KN之后,裂纹起裂并迅速扩展；裂纹起裂后,冲击力开始不断下降。在冲击载荷作用下,裂纹尖端的应力强度因子在起裂后会出现瞬间减弱的现象,这与裂纹尖端大量的微裂纹被“活化”有关系；但随着裂纹的继续扩展,裂纹尖端的应力强度因子又再次上升。裂纹的扩展速度在起裂后的扩展过程中基本保持匀速扩展,仅在距离边界一定范围内才出现快速下降的现象。

Study on Dynamic Fracture Behaviors of NSCB Specimen under Impact Loading

The new experimental system of digital laser dynamic caustics was used, a series of experiments were conducted on polymethyl methacrylate (PMMA) using a notched semi-circular bend (SCB) specimen with a center crack of 10 mm. The results show that: the impact load was increasing before the crack initiation; until it reached the maximum 4.8KN, the crack began to initiate and propagate; the impact load was decreasing after the crack initiation. Under the impact load, the stress intensity factor at crack tip of specimen decreased rapidly, because the micro-cracks were activated; but when the cracks continued to propagate, the stress intensity factor at crack tip of specimen increased again. In all crack propagation, the velocity is almost same, but it decreased gradually when it propagated to the boundary.