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Application of Friction Shear Test for Constitutive Modeling Evaluation of Magnesium Alloy AZ31B at high Temperature

Sanabria, Vidal; Gensch, Felix; Müller, Sören

FG Metallische Werkstoffe

The experimental determination of the flow stress and its mathematical formulation are essential for the numerical simulation of metal forming processes. The hot compression test is widely used to analyze the flow stress evolution as function of temperature, strain and strain rate. The compression test is limited to a relative low strain (ε≤1) which is acceptable when the stress is minor influenced at higher strains. In the case of magnesium alloys the flow stress is strongly influenced by the strain even at high strain (ε>1). In this work the thermo-mechanical behavior of the magnesium alloy AZ31B was investigated to improve the constitutive modeling up to high strains. Experimental stress-strain curves obtained from hot compression tests at different temperatures (450 °C-550 °C) and strain rates (0.01 1/s – 10 1/s) were applied to construct conventional material models such as those proposed by Garofalo (Zener-Hollomon) and Hensel-Spittel. In addition, shear tests under sticking friction conditions were carried out at high temperature (400 °C-500 °C) and different shear speeds (0.1 mm/s - 10 mm/s). During this test, the thin contact subsurface of cylindrical specimens experiences a high plastic shear deformation, while the axial force and stroke are simultaneously measured. Furthermore, a new constitutive modeling approach was proposed, which combine the Zener-Hollomon model and the experimental result of the friction shear test to estimate the flow stress at low and high strain respectively. Numerical simulations of the friction shear test applying the conventional models as well as the new constitutive formulation are presented in this study.