Laser-induced thickness stretch motion of a transversely constrainedirradiated slab

Abstract

This paper is concerned with the dynamic response of a transversely constrained, but arbitrarily thick slab due to a Holobeam model 630-Q Nd pulsed laser irradiation normal to the surface of the slab. The laser beam is assumed to be Gaussian in space and time. The laser beam energy density is adjusted to cause heating of the slab, but to avoid phase change (melting) of the slab material. The initial thickness stretch motion occurs in a time period that is very small compared to the gross motion of the thick slab with edges far away from the laser beam effective diameter. Hence, during the initial stages of the thickness stretch motion, the transversely constrained irradiated slab is considered a one-dimensional problem through the thickness with a uniform laser irradiation over the effective laser beam diameter. Solutions are obtained for the time-dependent deformation and stress fields through the thickness of the slab within the framework of classical uncoupled dynamic thermoelasticity theory and classical methods in boundary value problems. The plots confirm a wave nature of deflections that various points through the thickness are undisturbed until the wave reaches the points. Also, interesting observations are made regarding sign reversals of the deflections and stresses that are useful for the designers.