This paper describes the experimental application of a phased optical fiber array to transmit pulsed laser light to the free surface of Carborundum CS-3 ceramic samples for ultrasonic nondestructive evaluation (NDE). The pulsed laser beams heat the surface of the ceramic rapidly, and can thermoelastically generate longitudinal, shear, and surface (Rayleigh) waves. Without the optical fiber array all three wave modes are generated simultaneously, and no control over directivity or beam-width is possible. The experimental results presented here indicate that the wave modes, beam-width, and directivity of the generated ultrasound can be controlled by using the phased optical fiber array. Experimental directivity patterns for the laser phased array are compared to a simple theoretical model based on Rose’s point source theory. The model predicts shear wave directivities better than either longitudinal or surface waves. This work demonstrates some of the capabilities and limitations of using laser-phased arrays on ceramics.
Relation:
Journal of nondestructive evaluation 16(1), pp.1-9
