Computational simulation of the hypervelocity impact of Al-spheres on thin plates of different materials

Impact of materials at high velocity results in big craters, large deformations of structures and, at very high velocities, in a phase transition of the materials. Therefore a computational simulation of these events demands a stable and highly elaborate numerical method. A code used for this application requires major capabilities: the material model must provide different strength and failure models and include phase transitions. The other point concerns the numerical method used to trace the material motions. Regarding the large deformations regular Lagrangian codes fail. Eulerian codes contain the handicap of huge computation times and less accuracy at the calculation of both history dependent strength/failure status and displacements. Therefore we developed the gridless particle code SOPHIA running the so-called Smooth particle Hydrodynamics (SPH). State variables are calculated at grid independent interpolation points (particles). A Lagrangian formulation is used to describe the motion of the particles. Thus a grid independent Lagrangian code is obtained. Experimental data performed at the Impact Physics Division of the Ernst-Mach-Institut are used for the comparison with results of the numerical simulation. Flash X-Ray pictures of the debris clouds behind target plates made of copper and aluminum are the basis of the comparison. The debris clouds are formed by the normal impact of 10-mm Al sphere on a 4-mm Al plate at a velocity of 6.18 km/s and a 15-mm Pb sphere on a 6.3-mm Pb plate at 6.6 km/s respectively.