A Simplified Model for Thermal Shock and Spallation in Partially Transparent Elastic Materials under Energetic Radiation

摘要

In an elastic half space, thermal shock can be induced by radiant energy deposited into the material at some depth below the surface. The present paper considers plane wave motion set up by such a shock which is assumed to produce instantaneously a constant temperature rise above ambient to a certain depth below the surface and zero temperature rise at greater depths. This assumption of a rectangular pulse in space enables the wave motion to be followed by simple formulas and diagrams. It is demonstrated that the initial compressive stresses produce a tensile pulse of half the initial amplitude, and that the waves proceed without imparting net momentum to the medium. If fracture occurs in tension, part of the material will spall, and a solution is obtained for the wave motion following the first spallation. It is shown that a second and multiple spalls can arise if there is a delay time associated with fracture which is of the right order of magnitude. The delay time acts to decrease the amount of momentum carried off in the spall and so to retain part of the tensile wave for further spallation. (Author)