ON THE ACOUSTICAL LONGITUDINAL VIBRATION MODES OF FINITE CYLINDERS

Experimental measurements have been carried out on natural vibration f requencies of steel and aluminum cylinders of diverse radii and length s in symmetric longitudinal modes. A new method of noncontact detectio n has been used, based on speckle heterodyne interferometry. As oppose d to other authors' experiments, these experiments do not only include slender specimens but include diameter-to-length ratios in the interv al from 0.0156 to 0.6254. A study was performed using the results of t he experiment. The relationship between the frequency and some variabl es of interest were analyzed and the dispersion of the velocity was de termined. A systematic dependence of the wave velocity on the diameter was observed, even for small diameter-to-wavelength ratios. The resul ts obtained were compared with the theoretical ones for infinite rods and limits were established for those the commonly used simplified the ory may not be applied to. These results can be used to determine the Young's modulus from the frequencies of the longitudinal modes.