Study on the behavior of elastic-plastic fracture under mixed I plus II mode loading in aluminum alloy Ly12-J-integral analysis

The elastic-plastic fracture behavior of aluminum alloy Ly12 under mixed III mode loading was studied by finite element method and fracture test. A m ixed mode elastic-plastic fracture criterion of J-integral was proposed by using the J-resistance curve, and the maximum fracture effective plastic st rain epsilon(p max) of different mixed ratios at crack tip were also calcul ated. The results show that, (1) the initiation J-integral values of different mixed ratios have the equ ation [GRAPHICS] where J(li) and J(IIi) are the mode I and mode II components of the mixed i nitiation J-integral J(MC) at a constant mixed ratio, respectively: (2) the relation between the J(MC) and mixed ratio K-I/K-II is J(MC) = K-I(2) J(IC)/(K-I(2) + alpha K-II(2)) + alpha K-II(2)) + alpha K-II (2)) + alpha K-II(2) J(IIC)/(K-I(2) + alpha K-II(2)), where alpha = J(IC)/J(IIC); (3) J(MC) increases with an increasing of mode II component, J(IIC) is twic e of J(IC) for Ly12; and (4) the maximum fracture effective plastic strain epsilon(p) max and stress triaxality sigma(m)/sigma of different mixed ratios at crack tip satisfy t he formula of epsilon(p) (max) exp(3 sigma(m)/2 sigma) = constant, where the constant is about 9.52 for Ly12. The relation with double paramet ers, epsilon(p) (max) and sigma(m)/sigma, can be used as the local fracture or damage mechanics parameter under mixed mode I+II loading.