SINGLE-PULSE LASER EXCITATION OF STRUCTURAL VIBRATION USING POWER DENSITIES BELOW THE SURFACE ABLATION THRESHOLD

This paper describes sub-ablation optical excitation of flexural vibra tion in cantilevers and a suspended truck-wheel rim by using a single 600 mu s, Nd:glass laser pulse with energies between 1J and 40J. The e xcitation is consistent with the photothermal production of a localize d thermoelastic bending moment at the site of the laser irradiation. T his method of excitation has been combined with fibre optic sensing an d modal analysis of the resulting vibrations to provide a practical me thod of remotely measuring the structural properties upon which the fr equencies of vibration depend. The modal frequencies of slot-damaged c antilevers are presented to demonstrate the possible application of th is non-contact measurement technique for non-destructive testing. (C) 1995 Academic Press Limited.