Evaluation of J-integral Value by Using Finite Element Method

The J-line integral value proposed by Rice is used as one of the useful fracture toughness parameters for the ductile metals under the large scale yielding. Since the J-line integral values can not be obtained experimentally, Rice and Merkle, Corten proposed the formulas to evaluate the J-values for the center cracked specimen (CCS) and the compact tension specimen (CTS) from the single load-displacement curve, that is to say, the equivalent energy method (EE method). But, it is not clear that the J-line integral has the path independence and the J-values (J_E) evaluated by EE method are equal to the J-line integral values (J_R) under the general yielding. In order to assess the path independence of J_R and the equality on the J_E with J_R, the authors attempt to caluculate the J_R-values by using the Finite Element Method (FEM) based on the incremental strain theoly. Moreover, to ensure the accuracy of the numerical results by means of FEM, these results are compared with the experimental ones for 1.2mm thick SUS 430 stainless steel sheet specimens (CCS and CTS) such as load-displacement curves and the strains of thickness direction. As the results in this study, the J-line integral value evaluated on a contour remote from the Intensely Deformed Nonlinear Zone has the path independence and the J_E-values are fair agreement with the J-line integral ones.