ASA 125th Meeting Ottawa 1993 May

4aSA4. Laser vibrometer methods for measuring far-field structural intensity.

Timothy E. McDevitt

Appl. Res. Lab., Penn State Univ., P. O. Box 30, State College, PA 16804

There is a need to develop measurement techniques that can quickly and accurately provide structural intensity data over an entire surface without interfering with the structural response. To this end, methods have been developed to measure the flexural intensity in a reverberant beam by using scanning laser vibrometry; kinetics and standing wave methods have been employed with a single scanning vibrometer while a finite difference method has been employed with a two-channel scanning vibrometer. Experimental results for the first two methods, which each provide a single value of intensity on the beam, are compared with experimental results for the finite difference method, which was used to provide values of intensity at various positions along the beam. Similarly, experimental data on intensity in longitudinal waves along a rod are also presented for the vibrometer(s) set in the differential Doppler mode. Results indicate that flexural intensity is measured very consistently by the three methods and that longitudinal intensity measurements are feasible if the longitudinal motions, induced by bending waves, are taken into account. [Work supported by ARL Penn State.]