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

本研究的目的是建立实用的结构强度测量技术。本研究提出了一种用于结构强度测量的k空间信号处理和超声多普勒测振仪阵列。得到了以下结果：1. K空间法将结构强度的导数定义为固体结构中的振动能量流，其中包含了弯曲振动位移的高阶空间导数。这种计算对测量精度有很大的影响。该方法的优点是利用空间傅里叶变换，只需在k空间进行简单的运算即可估计出空间导数，并通过k空间滤波来降低振动噪声。为了避免加载对试样的影响，使用了激光多普勒振动计，这是最有前途的候选人之一。我们得到的重要结果是，k空间滤波的截止波数应是被测振动波数的1.5，以尽量减少测量数据中的误差的影响。通过梁和二维平板的实验验证了这一结论。2.超声多普勒换能器阵列提出了一种利用超声多普勒方法测量结构强度的新探头。由于超声系统比光学系统便宜、操作方便、对试样无加载效应，因此该探头适合于制作大阵列系统。制作了用于一维和二维测量的阵列探针。在振动频率为1 kHz时，该阵列的工作范围为3 mm/s-1.0m/s。通过一维和二维结构强度的测量，证实了利用多普勒效应的超声换能器阵列的有效性。

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.