A Quantitative Theory of Laser-Generated Ultrasound

Laser Generated Bulk Waves in Plates

“…In the past, the time dependence of the Iaser pulse has often been assumed to be [ 4,5,6,7] ( t )3 -2g f ( t) = ~ e t, tr = rise time . (5) While this is a reasonable approximation, Laplace transfonning equation 5 is a tedious task.…”

“…a 1 = 1.75 used in this work (6) which is, analytically, somewhat easier to Laplace transfonn. Further, the Laplace transfonn of variable s, which requires more work to invert numerically than does the Laplace transform offiquation 6.…”

“…While McDonald's model [4,5] was comprehensive, he considered only on-epicenter waveforms. Schliechert et al [6] calculated and measured waveforms at a wide range of observation angles in hemispheres, which emulates half-space solutions. Spicer [7] later calculated and measured waveforms in aluminum plates, but only for the out-of-plane displacement.…”

“…Comprehensive numerical models are needed in order to quantify the waveforms generated by laser sources in the thermoelastic regime, and as an aid in designing nondestructive materials evaluation systems. Comprehensive models have been developed, for example by McDonald [4,5], Schliechert et al [6], and Spicer [7]. These numerical models have been experimentally confirmed by a nurober of researchers, including Schliechert et al [6] and Spicer [7].…”

Analysis of Laser Ultrasonic Measurements of Surface Waves on Elastic Spheres

“…A pulsed laser can generate ultrasonic waves in a target by two methods: the creation of a transient subsurface thermal expansion (thermoelastic) and surface evaporation (ablation) [4][5][6][7]. In this study, a volatile liquid coating was applied to the surface of a sphere and ablated by the laser pulse.…”