A note on frictional release in microcracks

This note examines the behavior of microcracks in ceramics with inhomogeneo us friction on the crack faces and with dynamic loading. Since sound speeds in ceramics are very high (about 10 microns per nanosecond), cracks of the size envisioned (something like 1 to 10 microns in length) are fully envel oped by a wave in times of the order of a nanosecond or less, and therefore , should be considered as responding more or less statically, even in the p resence of shock waves where rise times may only be several nanoseconds.