Analyzing the total structural intensity in beams using a homodyne laser Doppler vibrometer

Agnaldo A. Freschi; Allan K.A. Pereira; Khaled M. Ahmida; Jaime Frejlich; Jose Roberto de F. Arruda

doi:10.1117/12.307721

1 June 1998 Analyzing the total structural intensity in beams using a homodyne laser Doppler vibrometer

Agnaldo A. Freschi, Allan K.A. Pereira, Khaled M. Ahmida, Jaime Frejlich, Jose Roberto de F. Arruda

Proceedings Volume 3411, Third International Conference on Vibration Measurements by Laser Techniques: Advances and Applications; (1998) https://doi.org/10.1117/12.307721
Event: Third International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 1998, Ancona, Italy

Abstract

The total structural intensity in beams can be considered as composed of three kinds 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 its contribution to the total structural intensity flowing through the beam. In this paper, a z-shaped beam is used in order to allow the three kinds of waves to propagate. The contributions of the structural intensity due to the three kinds of waves are computed from measurements made over the surface of the beam with a simple homodyne interferometric laser vibrometer. The optical sensor incorporates some additional polarizing optics 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 to detect nearly all backscattered light collected from the object. 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.

Citation Download Citation

Agnaldo A. Freschi, Allan K.A. Pereira, Khaled M. Ahmida, Jaime Frejlich, and Jose Roberto de F. Arruda "Analyzing the total structural intensity in beams using a homodyne laser Doppler vibrometer", Proc. SPIE 3411, Third International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (1 June 1998); https://doi.org/10.1117/12.307721

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KEYWORDS

Laser Doppler velocimetry

Ferroelectric polymers

Doppler effect

Wave propagation

Sensors

Signal processing

Homodyne detection

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