THEORETICAL AND EXPERIMENTAL STUDY OF LOW-VELOCITY PENETRATION PHENOMENA.
UTAH RESEARCH AND DEVELOPMENT CO INC SALT LAKE CITY SALT LAKE CITY
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Progress is reported on the development of a computer code for describing the flow field during impact of solid on solid. A one-dimensional material model is used consisting of isolated mass points connected by springs with highly non-linear spring constants and viscous damping. The spring constant is derived from shock Hugoniot equation-of-state work and the viscosity comes from measurements of the energy involved in crushing discs of the material used. So far, aluminum has been the only material tested in the computer program. The results of varying the predictorcorrector scheme used to stablize the solution and the results by varying viscosity are presented. It is shown that the solution gives the correct pressure jump across a shock front and gives correct wave velocities. Some oscillations and propagation of error are present. Methods of improving this are discussed. A rod-to-rod impact experiment is described for measuring the maximum pressure gradient which a material can sustain under dynamic impact conditions. The method is suitable for measuring material-strength properties for brittle materials which are not suited to the disc-crushing experiments previously used. Results are presented for nylon, polypropylene, plexiglass, Benelex, and glass. The plastics show a maximum pressure gradient, then a leveling off as impact velocity is increased. Glass increases continually up to the maximum velocities tested. Further work to increase the pressure used in the tests and to investigate geometric effects is outlined.