Modeling of high temperature Hopkinson tests on AA5083 and Ti6Al4V

Abstract
In the present work, dynamic tests have been performed on AA5083 and Ti6Al4V alloy specimens by means of a split Hopkinson pressure bar (SHPB). The impact behavior was investigated for strain rates ranging from 1000 to 1800 s⁻¹, and temperatures in the range from 100 to 300°C. A robotized sample device was developed for transferring the sample from the heating device to the position between the bars. Simulations of the temperature evolution and its distribution in the specimen were performed using the finite element method. Measurements with infrared camera and additional thermocouples added inside the sample were performed in order to validate the FEM simulations. The results show that a thermal gradient is created inside the sample and that the average temperature loss during the manipulation of the sample is rather large. These results also strongly depend on the alloy composition. In a last stage, an optimal set of material constants for the Johnson-Cook constitutive model has been computed by fitting, in a least square sense, the numerical and experimental stress-strain curves and has been implemented in a hydrocode for validation using a simple impact problem.