Abstract
KEYWORDS – Magnesium alloy sheet, Tension-compression tester, Twin, Un-twin, Non-isothermal stamping analysis
ABSTRACT – Magnesium alloy is one of the lightest materials used for structures. Its use is increasing in various industries, but its universal application has been limited by poor formability and large springback at room temperature. Depending on the temperature, Mg alloy sheet exhibits significant differences in tensile and compressive yield stress, as well as variation in its hardening behavior. These behaviors are more pronounced at room temperature, with metal-like properties evident at temperatures above 150°C. Such unusual behavior makes it difficult to simulate the forming process of Mg alloy sheets. Analysis results tend to deviate significantly from the experimental data because commercial softwares do not completely implement the unusual hardening behavior, yield asymmetry and temperature dependent changes in the material properties of the Mg alloy. In the previous study, new constitutive equation was suggested to analyze the unusual behavior, and implemented in the commercial softwares as the form of user subroutine. In this paper, an in-plane tension–compression tester was developed to predict the tension–compression behavior of Mg alloy sheets at the elevated temperature up to 250°C. These test results were used for warm forming analysis of cross-shaped cup, which was the NUMISHEET 2011 benchmark model. From the analysis, we determined the optimal stamping temperature and boundary conditions.