Mixed-mode fracture behavior of AM60 magnesium alloy using two parameter fracture mechanics

Abstract

The main objective of this study is the precise estimation of the fracture parameters by applying crack-tip constraint under mixed-mode loading conditions. To this aim, an AM60 magnesium alloy with elastic-plastic behavior has been utilized. Fracture tests were conducted using a modified version of Arcan device in mode-I, 45° mixed-mode, and mode-II loading conditions. Different initial crack lengths were used to create a wide range of crack-tip constraints. In addition, experiments have been carried out at different temperatures to enhance the applicability and effectiveness of research in real applications. Using finite element analysis (FEA), the crack-tip constraint, Q, corresponding to the laboratory conditions was extracted. The results show a strong dependency of Q constraint on the loading angle so that by changing the loading angle from mode-I to mode-II, the crack-tip constraint experienced a significant increasing trend, while the dependency on the crack length and temperature is negligible. Finally, the J-Q curves are presented for different temperatures and the corresponding relations are used for predicting the critical values of the J-integral in a specific condition and the obtained results are compared with the experimental results. According to the results, the minimum and maximum differences between the obtained results from the relations and the experimental result are 0.01% and 19.49%, respectively. Moreover, the J-R resistance curve has been modified using the crack-tip constraint. Regarding the obtained results, the minimum and maximum differences between the extracted values and the experimental results were 15.76% and 17.66% respectively. It can be concluded that using the results of this research eliminates the need for conducting the corresponding experimental tests, and the critical values of the J-integral can be obtained with reasonable accuracy by calculating the crack-tip constraint through FEA.