An Experimental Study on the Elastic–Plastic Fracture in a Ductile Material under Mixed-Mode Loading

Abstract:  Stereo vision was used to measure the crack-tip parameters, such as J integral, plastic mixity and elastic mixity of mixed-mode fracture specimens, and to study the applicability of the Shih's plane strain solution to the mixed-mode crack-tip fields. The fracture specimen used in this study was a compact tension shear (CTS) specimen made of 2024-O aluminum. The in-plane strain and stress fields near the mixed-mode crack tip of the CTS specimen were determined using the deformation field measured by the stereo vision. It is observed that the J integral values computed along rectangular contours surrounding the mixed-mode crack-tip approach constant values after r / h  > 0.5. The in-plane strains determined experimentally at several points near the crack tip and at several radial lines emerging from the crack tip are compared with the values calculated using Shih's plane-strain solution and the HRR slope, named after the investigations of Hutchinson, Rice and Rosengren respectively. It is found that the measured values follow the trends of the Shih's plane-strain solution. The elastic mixity evaluated using the measured crack-tip stress fields is close to that obtained from analytical solution. However, the evaluated plastic mixity deviates from the analytical solution.