Accession Number : AD0675645

Title :   A SIMPLIFIED MODEL FOR THERMAL SHOCK AND SPALLATION IN PARTIALLY TRANSPARENT ELASTIC MATERIALS UNDER ENERGETIC RADIATION.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF THE AEROSPACE AND MECHANICAL ENGINEERING SCIENCES

Personal Author(s) : Nachbar,W.

Report Date : MAY 1968

Pagination or Media Count : 38

Abstract : 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)

Descriptors :   (*THERMAL SHOCK, WAVE PROPAGATION), SPALLATION, THERMAL STRESSES, COMPRESSIVE PROPERTIES, TENSILE PROPERTIES, FRACTURE(MECHANICS), TEMPERATURE, ELASTIC PROPERTIES, RADIOFREQUENCY POWER, MATHEMATICAL MODELS

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE