The propagation of stress waves through a chain of discs has been studied experimentally using a high-speed photoelastic diagnostic technique and strain gauge measurements. An optically transparent single straight chain of 20-mm diameter discs, made of epoxy, was impacted in a vertical shock tube by an air shock wave. The fringe patterns of the stress field were recorded using a Q-switched YAG laser, a transmission polariscope and a CCD cameras. The incident shock wave reflected head-on from a puncher plate that was placed on top of the discs chain inducing behind it a fairly uniform step-wise pressure pulse. The duration of this pressure pulse acting over the puncher surface lasted for about 6 ms. Experiments indicated that inside the discs-chain the step-wise pressure pulse was broken into several oscillating cycles composed of transmitted and reflected stress waves that were followed by transmitted and reflected rarefaction waves. The back and forth bouncing of these waves continued until the overall stress within the discs-chain reached equilibrium with the compression force acting on the puncher plate. The stress wave propagation velocity along the discs chain was significantly lower than the appropriate speed of sound of the material from which the discs were made.
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