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

摘要

The absorption of electromagnetic radiation within a thin surface layer of an elastic half space 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,uniaxial motion,and where the radiant pulse duration is small compared to the wave travel time through the layer which,in turn,is assumed small compared to the characteristic times of thermal equilibrium 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,which are obtained describing the propagation of the resulting stress discontinuity,give considerable information on the influence of viscoelasticity. Complete wave forms 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 peak tensile stresses in the layer;compressive stress distributions,on the other hand,remain relatively unaffected. (Author)