Simple multiaxial tests to assess dynamic ductility of 17-4PH

To investigate material ductility, the use of simple multiaxial specimens which can be tested through a common tensile machine or by a Split Hopkinson bar facility would allow avoiding the use of more complex equipment to induce different stress states in the investigated material. In this work, experimental dynamic tests have been performed on four different specimen geometries on a 17-4PH steel by a direct Split Hopkinson Bar (SHB). Finite element models of the experiments are set up and used jointly with experimental data to calibrate and validate a strain rate dependent plasticity model, and to extract the local values of stress and ultimate strain in the most critical point of the samples, at fracture. These latter results allowed the calibration of a ductile damage model, whose predictions, compared with a previous calibration using tests carried out in quasi-static conditions, confirmed the effectiveness of the proposed specimens and test methodology to assess material ductility under dynamic conditions.