The development of the measurement method for a structural intensity with with a K-space signal processing

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The Purpose of this research is to establish the practical technique of structural intensity measurement. In this study, the k-space signal processing and ultrasonic Doppler vibrometer array for structural intensity measurement have been proposed. We have obtained the following results.1.K-space method The derivation of structural intensity defined as vibration energy flow in solid structure contains the higher order spatial derivatives of displacement for flexural vibration. This calculation has a large effect on the measurement accuracy. In the proposed method, there are some merits that the spatial derivatives can be estimated only by the simple arithmetic in k-space using spatial Fourier transformation and that vibration noise can be reduced by k-space filtering. In order to avoid the loading effect on the specimen, a laser Doppler vibrometer was used which is one of the most promising candidates. We obtained the important result that the cutoff wave number for k-space filtering should be one and a half of the wave number of the measured vibration to minimize the influence of error in the measured data. This result was confirmed by the experiments for a beam and 2-dimensional plate.2.Ultrasonic Doppler transducer array We proposed a new probe for structural intensity measurement using ultrasonic Doppler method. This probe is suitable to make a large array system, since the ultrasonic system is to easy handle and cheaper than the optical one and has no loading effect to specimens. The array probes for 1-dimensional and 2-dimensional measurements were made. The usable range of these array is 3 mm/s-1.0m/s at vibration frequency 1 kHz. The validity of the ultrasonic transducer array using Doppler effect is confirmed experimentally by the 1-dimensional and 2-dimensional structural intensity measurements.