STRESS WAVES IN A TEMPERATURE-DEPENDENT VISCOELASTIC HALF-SPACE SUBJECTED TO IMPULSVIE ELECTROMAGNETIC RADIATION

The absorption of electromagnetic radiation within a thin surface layer of an elastic halfspace results in a sudden heat-source distribution through the layer, and stress waves are generated; in particular both tensile and compressive stress are developed. In this paper the effect of viscoelasticity on the tensile stress build up in the absorption layer is studied for the case of a free surface, uriiaxial motion, and where the radiant pulse duration is small compared to the wave-travel time through the layer that, in turn, is assumed small compared to the characteristic times of thermal relaxation and ablation, if any. The radiation induced temperature is. assumed to decay exponentially with depth. The viscoelastic model employed is a temperature-dependent standard linear solid incorporating the shift hypothesis. Explicit closed-form results describing the propagation of the resulting stress discontinuity give considerable information on the influence of viscoelasticity. Complete waveforms are obtained numerically for a number of special cases with the aid of the Laplace transform. The cases studied indicate that viscoelasticity can significantly attenuate the peak tensile stress in the layer, while the compressive stress distribution remains relatively unaffected. © 1969 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.