Doctoral Dissertations

Summer 1997

Dissertation

Degree Name

Doctor of Engineering (DEng)

Department

Mechanical Engineering

Eugene Callens

Abstract

The purpose of this work is to delineate some of the physical mechanisms which govern the effect of nosetip shape on terminal ballistics phenomenology. A principal goal in the study of terminal ballistics has been the prediction of depth of penetration and crater diameter for penetrators and targets of various geometries, sizes, and materials. The model developed here is based on a "quasi-steady wave" mechanics approach to the problem with a 1-D model for the penetrator and a 2-D model for the target. The model is based on the application of the conservation of momentum equation to a control volume around the penetrator-target interface, and the application of both the momentum and continuity equations to control volumes around the disturbance waves in the penetrator and target.

The nosetip shape is found to influence both the structural and hydrodynamic stresses in the target. The structural stress in the target is postulated to be inversely proportional to Poisson's ratio raised to the (1 + sin $\theta)$ power where $\theta$ is the average nosetip semi-angle based on frontal area. The hydrodynamic stress is determined by the integral control volume analysis to be proportional to $\rm(1-cos\ \theta).$ The effects of both of these terms are to reduce target resistance for smaller nosetip angles.

This work applies to metals, concrete, and ceramic materials for impact velocities ranging from zero to 7000 m/s. The analytical model was programmed and compared with experimental data. The predictions are nominally within the experimental uncertainty of the data.

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