Experiments have been conducted to examine the influence of an adjacent crater or craters on the perforation performance of a diameter D=20mm fragment simulating projectile (FSP). Five FSPs were fired sequentially at impact velocities of approximately 1000m/s into a 15mm thick mild steel plate. An increase in residual velocity of 13% compared to a single impact was observed when two sequential impacts were 29mm (1.4D) apart. An impact next to two craters with the same 1.4D spacing increased the residual velocity (compared to a single impact) by 57%. An energy balance equation was used as the basis for a generalised model. It was found that the influence of the adjacent crater could be predicted from a calculation of the reduction in sheared circumference and the reduction in target plug mass. From the model it was found that the minimum spacing to avoid the influence of an adjacent crater was 1.55D at 1300m/s. The model was extended to include the effect of more than one adjacent crater, and gave reasonably good agreement with the experimental results.
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