Mesoscale Analysis of Sintered Metals Fragmentation under Explosive and Subsequent Impact Loading

Sintered metal compositions are used in many applications, including shells of explosive warheads. The properties of the compositions depend on both the base materials and the fabrication process. In order to achieve specific strength and fragmentation properties under dynamic loading, these parameters need to be optimized. We present a strategy to facilitate this process by numerical analyses on the meso scale for the case of the fragmentation of sintered metal cubes that shall survive an explosive launch and fragment into fine particles after perforation of a plate. This is an extension of work presented in [1], where only plate impact and different materials were regarded. The results are computed fragment size distributions for different base materials, grain size distributions, porosities and mesoscale material parameters like intergranular cohesive strength. The analysis is based on Hydrocode simulations with different numerical approaches and models for the launch and the impact phase. The transient pressures acting on the cube during the explosive launch from the warhead are evaluated from fluid-structure coupled computations on the macro scale. These transient pressures are then used as boundary conditions for a single cubic Representative Volume Element (RVE) in the mesoscale analysis of the launch phase. After the acceleration the same RVE impacts an aluminum plate at velocities of approx. 1100 m/s. In order to keep the computational effort feasible, scaling needs to be used. The validity of the scaling is checked by numerical simulations with different RVE sizes. Quantitative analyses of fragment size distributions are carried out.