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Thermoelastic Generation of Ultrasound by Line-Focused Laser Irradiation

Summary: Thermoelastic Generation of Ultrasound by
Line-Focused Laser Irradiation
Irene Arias and Jan D. Achenbach
Center for Quality Engineering and Failure Prevention, Northwestern University,
Evanston, IL 60208, USA
A two-dimensional theoretical model for the field generated in the thermoelas-
tic regime by line-focused laser illumination of a homogeneous, isotropic, linearly
elastic half-space is presented. The model accounts for the effects of thermal diffu-
sion and optical penetration, as well as the finite width and duration of the laser
source. The model is obtained by solving the thermoelastic problem in plane strain,
rather than by integrating available solutions for the point-source, leading to a lower
computational effort. The well-known dipole model follows from appropriate lim-
its. However, it is shown that, by simple elasticity arguments, the strength of the
dipole can be related a-priori to the heat input and certain material properties.
The strength is found to be smaller than that of the dipoles equivalent to a buried
source due to the effect of the free surface. This fact has been overlooked by some
previous researchers. Excellent quantitative agreement with experimental observa-
tions provides validation for the model. Some representative results are presented to
illustrate the generated field and provide insight into the relevance of the different


Source: Arias, Irene - Departament de Matemàtica Aplicada III, Universitat Politècnica de Catalunya


Collections: Engineering; Materials Science