裂尖塑性区内方向应变能裂纹扩展归一化准则

摘要

裂纹的起始扩展总是沿着裂纹的半径方向,在塑性区内半径方向的应变能能反映出材料的抵抗断裂的能力。对同一材料,不管它处于哪一种裂纹形式,它的断裂韧性参数是一个常量。本文引入了裂纹顶端临界扩展本征区。认为裂纹顶端存在一个决定裂纹扩展本征区,裂纹扩展是因为本征区的应力应变状态或损伤状态达到材料的断裂韧性才发生的。依此针对Ⅰ-Ⅱ复合型裂纹求出了不同裂纹倾斜角下,裂纹起裂角及归一化裂纹扩展应力σCπa/KIC,并与其它准则作了比较。仿真显示不同裂纹扩展准则下的归一化裂纹扩展应力随裂纹倾斜角β增加而显著减少。%The initial propagation direction of a crack is always along the radial direction at the crack tip,the radial strain energy in plastic core can reflect the anti-rupture ability of the material.The fracture toughness of a material is a constant whether which kind of crack type it is.And a concept of critical intrinsic zone of crack propagation was introduced,crack propagation happens when the tress or strain status of the zone reaches to the critical rupture value of the material.According to this concept,the mixed mode Ⅰ-Ⅱ initial crack angles and normalized crack propagation stress σcπa/KⅠC under different conditions were determined.The simulations show that the stress σcπa/KⅠC reduces significantly under different crack propagation criteria with increasing crack angle.