Study On Non-coupling Fracture Criterion Of AZ31 Magnesium Alloy During Thermal Deformation

As a typical lightweight metal,magnesium alloy has been widely used in medical equipment,electronic products,transportation,aerospace and other fields,and is the first choice material for automotive lightweighting.However,the magnesium alloy crystal structure is HCP structure,with less slip system,low strength,poor plastic deformation ability at room temperature,and brittle fracture easily occurs.Under heating conditions,the slip system increases and ductile fracture occurs.In this paper,AZ31 magnesium alloy sheet is taken as the research object.The combination of test and numerical simulation is used to study the feasibility of-non-coupling fracture criterion in the fracture prediction of AZ31 magnesium alloy sheet from both theoretical and experimental.It will be an an effective method to analysis failure of fractures.The fracture properties of AZ31 magnesium alloy sheet under multi-axis complex stress state was systematically studied.The specimens of four shapes were designed.Under simple tension conditions,the fracture properties of AZ31 magnesium alloy sheets under different temperature,different strain rates and different stress states were obtained..Under the premise of ensuring the consistency with the test results,the constitutive structure under each test condition is obtained through the inverse iteration method.Using ABAQUS software for unidirectional tensile simulation,the accurate fracture start position during the test process was obtained.The fracture of the flat specimen,flat notched specimen and pure shear flat specimen was at the geometric center of the gauge length.The tensile-shear composite flat specimen is at the notch of the gauge length section.And the material information such as the fracture strain,the stress triaxiality and the Lode angle parameter at this point was extracted.The feasibility of the uncoupled fracture criterion in the fracture prediction of AZ31 magnesium alloy sheet was studied,and the existing fracture models were theoretically analyzed.The Johsnon-Cook fracture model and the improved Cockcroft-Latham fracture model are selected as the research objects.And make a combined correction to include temperature T,strain rate(?),stress triaxiality η and Lode angle parameters (?) at the same time.It is concluded that the revised Johnson-Cook fracture model has higher prediction accuracy.