Development and Evaluation of Laser Doppler Techniques for Measurements ofFlexural and Longitudinal Structural Intensity

摘要

Based on the hypothesis that both flexural and longitudinal vibrational energyflow can be measured non-intrusively by an optical technique which can be extended to broadband vibrations, a two-channel laser vibrometer system is developed and evaluated for cross-spectral power flow measurements. The cross-spectral power flow results from tests on small resonant beams and rods are verified by comparison with one-dimensional energetics and standing wave power flow results (obtained with a single scanning laser beam of the two-channel vibrometer). Among the contributions of the thesis are: development and validation of the laser technique for measuring flexural power flow in reverberant fields; introduction of a procedure to maximize phase accuracy which eliminates phase bias error and coherent noise error; an investigation into the differential Doppler method for measuring longitudinal power flow including an analytical model of the effects of bending on the longitudinal power flow measurements; studies of the optical parameters which dictate the performance of the reference beam method and differential Doppler method; and a quantification of how physical and measurement parameters affect the accuracy of this nonintrusive two-point vibrational power flow measurement.