Affiliations: Departamento de Mecanica Computacional, FEM,
Universidade Estadual de Campinas C.P. 6122, Campinas, SP, 13083-970
Brazil | Laborat\'orio de \'Optica, IFGW, Universidade Estadual
de Campinas, Brazil
Abstract: The total structural intensity in beams can be considered as
composed of three types of waves: bending, longitudinal, and torsional. In
passive and active control applications, it is useful to separate each of these
components in order to evaluate their contribution to the total structural
power flowing through the beam. In this paper, a twisted
z-shaped beam is used in order to allow the three types of
waves to propagate. The contributions of the structural intensity, due to these
waves, are computed from measurements taken over the surface of the beam with a
simple homodyne interferometric laser vibrometer. The optical sensor
incorporates some polarizing optics, additional to a Michelson type
interferometer, to generate two optical signals in quadrature, which are
processed to display velocities and/or displacements. This optical processing
scheme is used to remove the directional ambiguity from the velocity
measurement and allows nearly all back-scattered light collected from the
object to be detect. This paper investigates the performance of the laser
vibrometer in the estimation of the different wave components. The results are
validated by comparing the total structural intensity computed from the laser
measurements, with the measured input power. Results computed from measurements
using PVDF sensors are also shown, and compared with the non-intrusive laser
measurements.
