Study of the relationship between J-integral and COD parameters under mixed mode I + II loading in aluminum alloy Ly 12

摘要

In this paper, the relationship between the J-integral and COD under mixed mode I+II loading was proposed and investigated. The J-integral was calculated by the Finite Element Method, and COD was defined by Rice's model and measured by a duplicating method in an aluminum alloy Ly 12. The critical values of the J-integral and COD for a stable mixed crack initiation were also determined by a resistance curve. It shows that: (1) the mixed J-integral, J_M and the mixed COD satisfy the relations of J_M = dn centre dot #sigma#_0 centre dot CTOD + ds centre dot #tau#_0 centre dot CTSD and J_M = d centre dot #sigma#_(yield) centre dot COD, where dn, ds and d are coefficients; CTOD and CTSD are the mode I and mode II components of COD, respectively; #sigma#_0 and #tau#_0 are the tensile and shear stresses at the crack tip strip, respectively, and (2) the initiation values of the J-integral and COD of mixed stable crack growth increase with an increasing mode II component, the J_(IIC) value is 2 times greater than that of J_(IC), and the COD_i for a pure mode II crack is 6 times greater than that of COD_i for a pure mode I crack.