Numerical investigation of single and multi impacts of angular particles on ductile surfaces

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Models of single and multi-particle impact(s) on metallic targets allow an understanding of fundamental erosion mechanisms. This work was focused on the creation of a three-dimensional finite element model of the single and multi-particle impacts on a ductile copper target using ANSYS Autodyn V. 14.57 tool. The finite element model was formulated in a Lagrange reference frame. Even at small initial impact velocities, the Lagrange formulation suffered from large material deformation and large element distortion. This resulted in an inefficient increase in simulation time. Therefore, element erosion approach was used to remove the highly distorted elements that were responsible for the time step problems. The copper plate was modeled with a shock equation of state in order to consider the shock propagation as realistic as possible. The Johnson–Cook strength model was used in combination with the Johnson–Cook failure model. Good agreement between simulation results and experimental data was obtained. Moreover, a parameter analysis was carried out by varying the initial input conditions. Erosion mechanisms, such as cratering by material pile-up and chip formation were observed. It was found that mainly the initial orientation angle of the particle θi, and the impact angle αi, determine the erosion mechanism. For a given constant impact angle αi, there is a specific initial orientation angle θs, in which the transition from kinetic energy into internal energy is maximized. For values of θi<θs, the particle rotated forwards after the impact with the copper plate. For initial orientation angles θi>θs, the particle rotated backwards after the impact. The modeling was performed with multi-particle impacts as well. It was found that the rising rate of penetration depth decreases gradually when the number of non-overlapping particle impacts has increased.