Comparison of Finite-Element Stress Analysis with Experimental Copper Sphere Impacts

摘要

Three copper spheres were impacted on targets of varying surface finishes at 100 m/s. Impact face friction was varied for each test and the impact was photographed with a high-speed camera. Postimpact strains and deformation were measured. A finite-element computer code, NONSAP, was used to model the impact. The best agreement between computer prediction and experiment was obtained using isoparametric elements, a graded mesh, and actual high-strain-rate copper stress-strain data. Frictional conditions at the impact face were also modeled by altering the standard NONSAP code. The most critical test of NONSAP was accurate prediction of experimental impact strains. The best agreement we could obtain had a maximum point-to-point error of 20%, although in general, the comparison was much better. Results of this research indicate that we must know more about material and impact interface friction in order to obtain reliable numerical predictions. (ERA citation 05:031726)