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A model for the ultrasonic detection of surface-breaking cracks by the Scanning

Summary: A model for the ultrasonic detection
of surface-breaking cracks by the Scanning
Laser Source technique
Irene Arias and Jan D. Achenbach
Center for Quality Engineering and Failure Prevention, Northwestern University,
Evanston, IL 60208, USA
A model for the Scanning Laser Source (SLS) technique is presented. The SLS is
a novel laser based inspection method for the ultrasonic detection of small surface-
breaking cracks. The generated ultrasonic signal is monitored as a line-focused laser
is scanned over the defect. Characteristic changes in the amplitude and the frequency
content are observed. The modeling approach is based on the decomposition of the
field generated by the laser in a cracked two-dimensional half-space, by virtue of
linear superposition, into the incident and the scattered fields. The incident field
is that generated by laser illumination of a defect-free half-space. A thermoelastic
model has been used which takes account of the effect of thermal diffusion, as well
as the finite width and duration of the laser source. The scattered field incorporates
the interactions of the incident field with the surface-breaking crack. It has been
analyzed numerically by a direct frequency domain boundary element method. A
comparison with an experiment for a large defect shows that the model captures


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


Collections: Engineering; Materials Science