Formation and Description of Debris Clouds Produced by Hypervelocity Impact

Forty-one light gas gun tests were performed to examine the formation of debris clouds produced by the hypervelocity impact of aluminum spheres with thin aluminum sheets at normal incidence. Two tests were performed with the bumper sheet at an oblique angle. All tests provided multiple-exposure, orthogonal-pair flash radiographs of the debris clouds produced by the impacts. The failure and fragmentation of the aluminum sphere was observed to be an orderly process. Measurements taken from the flash radiographs were used to determine: (1) the velocity of a number of characteristic points in the debris clouds; (2) fragment sizes; and (3) fragment-size distributions. Sphere diameter, bumper-sheet thickness, and impact velocity were the primary test variables. The effects of bumper-thickness-to-projectile-diameter ratio, impact velocity, and material on the debris-cloud formation process were evaluated. A collection of models was developed and used to describe the formation of various debris-cloud elements. A method for estimating the state of the material in a debris cloud was developed. Features observed in the radiographs of the debris clouds indicated that the estimation procedure was reasonable. Analyses of the holes formed in the bumper sheets and damage patterns produced on witness plates behind the bumpers complemented the analyses of the flash radiographs.