REMOTE EXCITATION AND SENSING OF MECHANICAL RESONANCES IN STRUCTURES USING LASER-DIODES AND AN OPTICAL-FIBER INTERFEROMETER

The non-contact excitation of resonant flexural oscillations in struct ures of significant size, using repetitive pulses from a low-power dio de laser, is reported. These vibrations are produced by photothermally induced bending moments which are of sufficient amplitude to produce deflections which are readily measured using a simple optical fibre in terferometer. The interferometer uses the reflected signal from the na tural surface of the structure and requires only that the surface be a ligned approximately perpendicular to the interferometer beam. Applica tions of this technique for non-contact, non-destructive testing for c hanges in properties such as size, shape and structural integrity are discussed.