不同角度裂纹缺陷对材料动态断裂行为的影响

Effect of Material Containing Crack Flaws on Dynamic Fracture Behavior

采用新型数字激光动态焦散线试验系统,对含相互垂直和相互共线两种裂纹缺陷介质在冲击载荷作用下的动态断裂行为进行了研究。结果表明:在动态冲击载荷的作用下,边裂纹缺陷处应力集中程度远大于试件的内部裂纹缺陷处应力集中程度;当裂纹从垂直内部裂纹缺陷的端部再次起裂时,表现为Ⅰ/Ⅱ复合型断裂;起裂后,裂纹的断裂模式很快由Ⅰ/Ⅱ复合型向Ⅰ型转化;而对于内部共线裂纹缺陷而言,裂纹的起裂和扩展始终表现为Ⅰ型断裂形式。当内部裂纹缺陷垂直于边裂纹时,内部垂直裂纹缺陷对边裂纹扩展的裂纹尖端的应力强度因子和裂纹扩展速度均有抑制作用;且当裂纹再次从内部垂直裂纹缺陷处起裂后,裂纹的扩展速度和应力强度因子也较共线裂纹缺陷时的高;裂纹扩展速度与裂纹尖端的动态应力强度因子呈正相关性。

By using new digital laser dynamic caustics test system, dynamic fracture behavior of the material containing perpendicular and collinear cracks defects under impact loading were studied. The results show that, under dynamic impact loading, stress concentration at the tip of edge cracks is much greater than those at internal cracks defects. When the crack propagated from the end of the vertical defect, which is mode Ⅰ/Ⅱ fracture, and crack fracture mode quickly turns from Ⅰ/Ⅱ to mode 1 after the crack initiation, but for the collinear defect, it is mode I fracture for initiation and propagation; vertical defect made stress intensity factor and the crack propagating velocity decrease, and when the vertical defect initiates again, stress intensity factor and the crack propagating velocity are more higher than those of collinear defects. The dynamic stress intensity factor is positively correlated with the crack propagating velocity.