The effect of current and speed on perimeter erosion in recovered armatures

This paper describes a continuation of earlier reported work in which C-armatures were launched and recovered for the purpose of studying melt-wave erosion (MWE) damage on the contact surface of the trailing arms. The purpose of the experiments reported here is to begin linking experimental results to theoretical predictions of the erosion process. Specifically, we sought to test a claim made in many of the two-dimensional (2-D) analytical models of MWE that the speed of the erosion front should be proportional to velocity and to the square of current. To this end, we performed two series of tests in which velocity and current were varied while controlling other variables. Peak currents ranged from 400 to 1200 kA, and exit speeds ranged from 100 to 700 m/s. Results reported include mass and volume of eroded material measured by mechanical profilometry and qualitative observations of the damage. The erosion rates are in reasonable agreement with the scaling relations predicted by 2-D theory. The erosion patterns, however, are qualitatively different from 2-D predictions.