Method for Accelerating Flat Plates to High Velocity

Abstract

High velocity plates are useful in research, especially in the study of matter under high pressure. A scheme has been devised and tested for driving a thinner driven plate to a higher velocity than a driver plate of the same impedance. The increase is obtained in a collision process in which the driver strikes a buffer layer of lower impedance which is backed by the driven plate. The complex wave pattern has been examined in the acoustic approximation of constant impedance to obtain estimates of the optimum impedance ratios for several configurations which do not spall the driven plate. Experiments with head‐on collisions observed by high speed photography and with oblique collisions observed by flash x radiography have demonstrated the technique in both single and multistage arrangements. The results agreed well with the acoustic approximation when the impedance ratio was evaluated at one‐half of the pressure level obtained in the initial impact of driver against buffer. Photographic observation of the plate surface indicated substantially no breakup over a free run distance sufficient for the plate to reach terminal velocity.