Abstract

Nondestructive inspection for surface cracks in turbine components has become an important aspect of electric power plant maintenance. We describe work sponsored by the Electric Power Research Institute, Palo Alto, CA, on two laser techniques for detecting and imaging such cracks, in one of these, photothermal radiometric imaging, which is applicable to off-line inspection, the surface is scanned by a heating laser beam, while the transient surface temperature at the heated spot is monitored radiometrically. Surface defects, even those lightly covered, are detected by a local rise in this temperature. The second technique, applicable to both off-line and on-line inspection, is an optical scattering technique that can provide information not only on the presence of a crack but also on its width.

© 1986 Optical Society of America