Influence Of Stress Triaxiality On The Fracture Behavior Of AZ31B Magnesium Alloy Under Quasi-static Loading

In this paper,the two forms of AZ31 B magnesium alloy material(bar and sheet)as the research object,was not intended to establish a stress fracture criterion,but aimed on the analysis of AZ31 B magnesium alloy fracture behavior through the experimental designs and the corresponding numerical simulation under different stress states.Also using fracture criterion for validation and comparison of references.The results of the bar have conformed broadly to the fracture criterion,but the sheet’s has a large degree of non conformity.Therefore,the influence of specimen geometry on fracture criterion was studied by five groups of numerical model with the aspect ratio of25:1,9:1,9:2,9:4.5,9:9.Firstly,the design and analysis of experiments are conducted for different ranges of stress triaxiality including test for low,medium and high value of stress triaxiality,the fracture strength,equivalent fracture strain of AZ31 B magnesium alloy under different stress states can be obtained;Secondly,the process of different tests were analyzed by numerical simulation,the sensitivity of the mesh size has been studied.The smaller the notch radius,the higher the sensitivity of the mesh size;In mesh size between 0.001 m and 0.005 m,the fracture length increases with the increase of mesh size;Then,the value of stress triaxiality can be calculated,thus the reasonable segmented function were selected according to fracture characteristics under different stress triaxiality.A more comprehensive and reasonable fracture criteria of AZ31 B magnesium alloy was established in the space of equivalent failure strain and stress triaxiality under different stress states,and the fracture criteria were validated as well as compared between the results and references,it is found that the bar’s is highly consistent with references and the plate’s is quite different from references;Finally,the influence of specimen geometry on fracture criterion is studied.the results show that the equivalent fracture strain and the fracture ductility increased with the decrease of aspect ratio of the cross section.Based on the results of numerical simulation,turning point curve of the equivalent fracture strain were obtained,the results provide a basis for the calculation of the equivalent fracture strain turning point.At the same time,some suggestions on the application and processing of magnesium alloy sheet were put forward.