Experimental evaluation and finite element simulation of explosive forming of a square cup from a brass plate assisted by a lead plug

A FE model is developed to simulate the experimental tests for the impulsive deep drawing of a brass square cup with the presence of a lead plug. The loading of the assembly is achieved by the detonation of a high explosive, underwater. The formability of the brass plate in the absence of the lead plug gives rise to material instability and uneven material thickness over the formed region causing rupture. The presence of lead plug initially slows down the forming process by acting as a reservoir for the kinetic energy. As the deformation progresses, kinetic energy in the plug is transferred to the plate and the increased time scale of the operation enables the system to be treated as a quasi static forming process. In addition to postponing the onset of material instability, the presence of the lead plug enables a higher ratio of drawability and a better uniformity in thickness of the formed dome. The experimental investigations have indicated that the optimum shape of the plate specimen is a square blank with circular cut-off segments. The effects of the medium impedance, wave reflection and refraction are considered to be negligible in order to improve the simplicity of the modelling procedure. Finally, the computed results are compared with those obtained from experimental tests.