An Anisotropic Axisymmetric Model for Wrought Magnesium Alloys

Global environmental concerns have put lightening of structures on the fore front of research in transportation industry. Among other light weight alloys, the transportation industry is considering magnesium intensive light body-in-white structure in automotive applications. Although the research in modeling technique areas is very active, a suitable practical model mimicking the severe asymmetry and anisotropy of magnesium is lacking. Loading-unloading behavior of wrought magnesium alloy over a wide range of strain has been obtained experimentally and subsequently presented here. It is shown that while the material behaves elastically isotropic, it shows a different yield in tension and compression with a high Bauschinger effect. This is attributed to the magnesium multiple deformation mechanisms of slip, extension/contraction twinning, and de-twinning resulting in an asymmetric yield and a directional dependent performance. Up-to-date there is no plasticity model commercially available that can capture this behavior. Therefore, it is necessary to develop a simple and efficient model that can serve as a benchmark tool for plasticity model evaluation. Such model is presented in this paper. The axisymmetric elastic-plastic model of Jahed and Dubey (1997) has been extended to wrought magnesium alloys. An asymmetric yield function is adopted and the obtained behavior in loading and unloading is directly incorporated in the solution process. It is shown that results are significantly different from isotropic assumptions.