F. Gascon et al., MEASUREMENT OF LONGITUDINAL VIBRATIONS IN A SLENDER ROD BY OPTICAL HETERODYNE INTERFEROMETRY, European journal of mechanics. A, Solids, 17(1), 1998, pp. 167-177
The vibration of a slender rod subject to a longitudinal harmonic pert
urbation without physical contact and near the first resonance frequen
cy is experimentally analyzed. The rod is excited by a magnetic field
which produces an harmonic force acting on a small ferromagnetic disc
glued at the end of the rod. The detection technique applied is based
on the optical heterodyne speckle interferometry, which permits both t
he normal-to-surface displacement and the tangential displacement to b
e detected sequentially. The out-of-plane technique is used to estimat
e the first eigenfrequency. By means of the in-plane technique the amp
litude and phase for different frequencies near resonance are measured
and the displacements of 17 equidistant points on the lateral surface
of the rod are plotted as a function of time. The comparison between
the experimental results and the prediction of the classical theory sh
ows a good agreement, making apparent the usefulness of the speckle in
terferometry for the vibration analysis. In addition, Young's modulus
is calculated and Poisson's ratio is estimated from the measurement of
both the out-of-plane and in-plane displacements of two opposite late
ral points of the rod. (C) Elsevier, Paris.