Approach of using a ductile fracture criterion in deep drawing of magnesium alloy cylindrical cups under non-isothermal condition

There have been many ductile fracture criteria published for predicting fractures in the isothermal metal-forming process, especially at room temperature. However, many materials, such as magnesium alloy and aluminium alloy, show an improved formability at elevated temperatures under non-isothermal conditions. It is significant to predict the occurrence of fracture in metal forming under these conditions since a forming limit diagram is almost powerless here. In the present work, an approach is proposed for extending the application of existent ductile fracture criteria in a non-isothermal metal-forming process. Using the new approach, combined with the finite element method (FEM), the deep drawing of magnesium alloy AZ31 cylindrical cups under non-isothermal condition is analysed. The fractures located in the punch radius region and in the cup wall close to the radius region of the female die resulting from the low and high punch temperatures, respectively, are predicted.