Stress Wave Propagation in Bars Due to Normal Impact on Water.

摘要

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.