Experimental investigations of space debris using Hypervelocity ballistic range HBR - 1

Hypervelocity impacts produce extreme pressures in both the projectile and target materials. In the present study the hypervelocity impact crater formation is investigated experimentally both from basic gasdynamic and metallurgical view points. The debris cloud generated by the impact of a 14 mm diameter high density polyethylene projectile flying at 4.0 km /s on a 2 mm thick aluminium alloy (2024) shield is visualized by shadowgraphy. The debris cloud formation is also simulated numerically using AUTODYNE ™ - 2Dhydrocode. Experimentally visualized debris cloud shape agrees well with numerical simulation results. Although the average value of Vicker's micro-hardness for AI 2024 is 138 Kgf/mm², in the vicinity of the edge of the impact crater the value increased to ~ 170 Kgf/mm². The increase in hardness due to strain hardening seems to be off set by localized adiabatic heating. Spallation and plugging rings are observed even on the back side of the target. Adiabatic shear bands which nucleate the cracks for spading, non- homogenous secondary phases of plastic deformation appear to be the possible mechanism of fracture in hypervelocity impacts.