A debris cloud cratering model

Abstract

A model is put forth to predict the depth of cratering penetration into a witness-block (WB) that has been loaded by a debris cloud generated from a projectile impact into an uprange bumper-shield (BS). The independent variables are debris cloud spray angle, radius to depth ratio of the WB craters, impact velocity, BS thickness to projectile diameter ratio, and BS/WB separation distance to projectile diameter ratio. The model is valid for impact scenarios where the debris material within the cloud is comprised of mostly solid fragments. Distributions for fragment size, shape, velocity and mass are implicitly combined and incorporated into the model by a single empirical parameter. This parameter is chosen so as to correlate to a large set of cratering depth data for aluminum. This parameter assignment also finds the model to closely match a small set of experiments with molybdenum as the projectile and BS material. The model is also adapted to the scenario of a high density projectile impacting a low density BS. Using the same empirical parameter assignment as for the aluminum and molybdenum cases the model is shown to also produce good results for a steel projectile and polymethyl-methacrylate BS.