伴随微孔洞生长的裂纹弹塑性定常扩展

ELASTIC-PLASTIC CRACK ADVANCE UNDER STEADY-STATE ACCOMPANIED BY THE MICRO-VOID GROWTH

裂纹在韧性材料中扩展时，将伴随着微孔洞的萌生和生长．孔洞的萌生和演化将直接影响着材料的总体断裂韧性和强度．以往的研究主要集中在将裂纹的扩展刻划为微孔洞的萌生、生长和汇合这样一个过程．从传统的断裂过程区模型出发研究微孔洞的萌生和生长对材料总体断裂韧性的影响，通过采用Ｇｕｒｓｏｎ模型，建立塑性增量本构关系，然后针对定常扩展情况直接进行分析．孔洞对材料断裂韧性的影响由本构关系刻划，而在孔洞汇合模型中，上述影响则由断裂过程区的改变来体现．研究结果显示出，微孔洞的萌生与生长将使材料断裂韧性降低并随着初始孔洞体积百分比的增大裂纹呈脆性扩展且发生损伤破坏．

When a crack propagates along the ductile material, a process of the void nucleation and growth will be accompanied. The global fracture toughness and strength of material will be influenced considerably due to void nucleation and evolution. Previous researches have mainly focused on the fracture process, in which crack advance is described by a process of the void nucleation, growth and coalescence. In this paper, based on the conventional fracture process zone models, the effects of micro-void nucleation and growth on the global fracture toughness are studied. In the research, a set of the increment constitutive equations of plasticity is derived based on the Gurson's model, and then used to the steady-state crack advance case directly. The effect of voids on the fracture toughness is described by the constitutive equations. The approach is different from that by adopting the void coalescence model, the effect is mainly expressed with the change of the fracture process zone. The results of present research show that the global fracture toughness of material will decrease with void nucleating and growing, and as the initial void volume fraction increases,crack propagates with brittle characteristics and material is in the void damage failure.