Fracture modelling of magnesium sheet alloy AZ31 for deep drawing processes at elevated temperatures

Abstract

Today, the reduction of CO2 emissions is essential to meet global climate requirements. In this context, a reduction in vehicle weight is the most efficient way to reduce the fuel consumption of a passenger car. Magnesium combines relatively high strength with low weight and is therefore an interesting construction material for lightweight solutions. In numerical process design, it is essential to be aware of the forming capacity of a material. The common method to describe the failure behaviour is the use of forming limit curve (FLC). Stress-based models offer the advantage of a strain path consideration and an extension in the area of shearing and compression. In this paper a stress-based damage model, Modified Mohr-Coulomb (MMC), was parameterized by IFUM Butterfly-Tests for an AZ31 magnesium sheet alloy under consideration of elevated process temperatures. For this purpose, the tests were carried out at different stress states and temperatures using a specially designed testing device. In addition, forming limit curves were determined by Nakajima tests. Finally, both methods, MMC and FLC, were compared to an experimental deep-drawing test. This comparison showed that the MMC Model achieved significantly better results regarding the fracture prediction in this application case.