Stress-generation and unloading properties of pulse-heated porous carbon determined by a side gauging technique

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Abstract
Measurement of the thermomechanical response of a porous carbon induced by a pulsed electron beam and the associated relief‐wave velocities for the stress pulse unloading are described. These measurements are sufficient to determine an effective Grüneisen coefficient for energy inputs to 500 cal/g. The measurements are accomplished with a new side gauging technique which does not require wave propagation out of the heated region of the sample. A laser interferometer system is used to detect the lateral displacement of a target free surface vs time for the microsecond time duration immediately following deposition. The displacement‐time measurement also permits detection of the unloading wave velocity in the heated material. Through use of a porous‐solid collapse model (the P‐α model), comparisons of the present results to computer calculations of the displacement‐time profile show significant differences from the observed wave profiles.