Stress Wave Propagation in Bars Due to Normal Impact on Water.
NAVAL SURFACE WEAPONS CENTER WHITE OAK LAB SILVER SPRING MD
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The stress wave response of solid, right circular cylindrical bars due to normal impact on an undisturbed water surface was investigated analytically and experimentally. The analytical problem was formulated as a two dimensional axisymmetrical elastic bar impacting on an initially perfectly flat, compressible water half space. Method of characteristics - finite difference solutions were obtained for the Lagrangian system of bar equations and Eulerian water equations, and programmed for computer solution. Strain-gaged magnesium bars were shot with a 3 inch diameter air gun into a chamber which was evacuated to the vapor pressure of water for preserving an undisturbed water surface prior to impact. Shots were made with a bare magnesium nose unmitigated and with rigid polyurethane foam noses of densities 5 and 15 pounds per cubic feet. The use of a foam nose greatly reduces the transmitted stress to the bar.
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