Elastic Precursor Decay in Quartzite for Cylindrical and Spherical Flow

摘要

When a shear‐yielding solid is subjected to impact or explosive loading, the propagating disturbance may consist of two distinct wavefronts. The first is the elastic precursor and the second is the plastic wave, which carries the material to the final stress. In solids which exhibit rate‐dependent stress‐strain behavior the precursor amplitude is not constant, but decreases with propagation distance. For plane shock waves this decay is due entirely to the rate‐dependent property of the material. However, for cylindrical and spherical shock waves there is additional attenuation due to geometrical divergence. The decay of the elastic shock wave in Sioux quartzite is calculated for plane, cylindrical, and spherical flow. If r0 is the radius of the cavity in which the disturbance is initiated, the equations of plane flow can be used with negligible error when r0 ≫ 50 cm for a cylindrical cavity, and r0 ≫ 100 cm for a spherical cavity. For an initial stress of 0.100 Mbar and a cavity radius of 5 cm, the precursor amplitudes at 5 cm from the cavity surface are approx 0.058, 0.041, and 0.030 Mbar for plane, cylindrical, and spherical flow, respectively.