Strength Estimates for High Velocity Penetration of Geological Targets by the Compaction Ring Theory

Abstract

Existing theories for rigid body penetration model the target response to a penetration process as a cavity-expansion. A new analysis, however, offers an innovative approach to rigid body penetration of porous geological targets. The theory analyzes the formation of a compacted ring of target material observed around the boreholes in recovered targets. Applying fundamental laws of motion to an element during the formation of the ring leads to estimates for the three stresses that control the penetration event. A retarding force on the projectile nose is derived and then used to arrive at an estimate for penetration depth. The penetration depth equation, resulting from this model, is dependent upon known projectile properties, target material properties, and the impact velocity. Neglected are the effects of friction and shear. The solving procedure returns an estimate for the target yield strength. The model can then be used to predict the penetration of any penetrator into the target material. The results are promising and in agreement with the experimental observations.