含缺陷材料冲击断裂的动态焦散线试验研究

采用新型数字激光动态焦散线试验系统,对固定倾斜角度不同离心率缺陷的PMMA试件进行了重锤冲击试验,研究含缺陷材料的动态断裂行为。研究结果表明:不同离心率的缺陷试件断裂形态基本相似;裂纹从试件下边界起裂,扩展至缺陷中部,发生停滞后由缺陷椭圆长轴上端点B继续起裂,直至贯穿整个试件。缺陷离心率的变化对裂纹的前期扩展没有明显的影响,对裂纹停滞时长及B点起裂时应力强度因子影响较大,缺陷离心率越大,停滞期时长越短。缺陷离心率的增大对缺陷端部的应力集中具有促进作用。

Dynamic Caustics Tests for Materials with Defects under Impact Loading

Using the test system of digital laser dynamic caustics, they run the hammer-drop tests to the PMMA specimens with the same inclination angel but different eccentricity flaws to analyze the dynamic crack behaviors of defective mediums. The results showed as following: the cracking shapes of defective specimens with different eccentricity flaws were basically the same; cracks started from the bottom, then propagated to the medium of defective specimen, and after sometime of stagnation, defective tip B started cracking until extending to the whole specimen. Eccentricity changes of defective mediums had no main effect on the initial stages of cracks, but on the contrary, they had obvious effect on the stagnation time and stress intensity factors of crack initiation at tip B. The more eccentricities at tips were, the shorter the stagnation time would be. The increase of the eccentricity at tips would accelerate the stress concentration at the ends of defective mediums.