DETERMINATION OF THE ELASTIC-CONSTANTS OF ISOTROPIC SOLIDS BY OPTICALHETERODYNE INTERFEROMETRY

An experimental method based on the application of speckle interferome try is proposed in order to determine the dynamic elastic constants of an isotropic material. A broad frequency spectrum impact is applied t o a cylindrical sample and, when this vibrates freely, a heterodyne la ser interferometer is used to detect the displacement of a point of th e material. Once the sample is suitably excited, the displacement comp onent of interest, either in-plane or out-of-plane, is detected in ord er to determine its frequency content. A spectral analysis allows the determination of the longitudinal, transverse, and torsional natural f requencies. From this the elastic constants are calculated. The measur ement precision is checked experimentally using the same method by mea ns of a third detection.