THERMO-MECHANICAL MODELLING OF DYNAMIC TENSILE EXTRUSION TEST

Recently, the researchers of the Los Alamos National Laboratory (LANL) have been developed a technique to investigate high strain-rates in which a sphere is launched at high speed (300-800 m/s) through a conical die (Dynamic Tensile Extrusion test). The system can use a set-up similar to a Taylor test (like a light gusgun) but induces in the material high levels of tensile stresses and allows to investigate the fracture and damage of the material in these extreme conditions. Due to the high strain-rates and hydrostatic component of stress that occur during the extrusion in the die, the material is also subject to a rapid heating. In this work, the DTE test has been simulated with the explicit Lagrangian code LSDYNA. In order to correctly reproduce the various aspects of the test it is necessary to use an elasto-plastic material model that takes into account strain-rate, thermal softening, pressure influence and damage and that adequately describes the thermal coupling effects and the equation of state (EOS) of the material. Besides, due to the high distortion of the Lagrangian mesh, the use of a mesh adapting technique is absolutely necessary