Development of Technique for Identification of Excitation Sources Using Vibration Intensity Method

在确定有效的机器噪声控制方法时，弄清噪声源及其贡献是很重要的。在机器结构中，施加在激励点上的振动能量通过梁和/或板传递，引起振动并作为噪声从其表面辐射。噪声源并不总是与结构中的激励点重合。因此，激励源和振动能量传递路径的识别可以给出噪声和振动控制措施的决定性信息。振动强度（VI）技术被认为是有用的。VI作为给定方向上每单位宽度的振动功率获得。将这种强度法应用于实际机械结构的故障诊断存在一定的困难。根据在不同点测量的一组振动数据计算三阶导数可能会引起误差。此外，振动能量流的瞬态特征，这是通常观察到的大多数实际结构，由于时间平均过程中丢失。本研究的目的是发展一种简化的测量技术，适用于实际机械结构中的VI测量。本文采用三通道虚拟仪器采集的包络线技术进行数据处理，分析了振动能流的瞬态特性。通过实验和有限元模拟，阐明了本方法在边界附近和曲板上的应用局限性。在应用范围内，对实际机械结构的振动强度进行了测量。成功地可视化了振动能量随时间的多路径传输。结果表明，本技术的应用，可以在诊断和实际机械结构的噪声和振动控制的信息。

In determining the effective ways for machine noise control, it is important to clarify the noise sources and their contributions. In a machine structure, the vibration energy exerted on the excitation point is transmitted through beams and/or plates, causes vibration and is radiated as noise from its surface. The noise sources don't always coincide with the excitation points in a structure. Therefore, the identification of excitation sources and vibration energy transmission paths can give a decisive information on the noise and vibration control measures. The vibration intensity (VI) techniques is thought to be useful for this purpose. VI is obtained as vibration power per unit width in a given direction. There are some difficulities in applying this intensity method to diagnostics for practical mechanical structures. The calculation of third-order derivatives from a set of vibration data measured at different points may cause error. Furthermore, transient features of vibration energy flow, which are generally observed in most practical structures, are lost due to the time-averaging process. The objective of this research is to develop a simplified measurement technique applicable to the VI measurement in practical mechanical structures. In the present research, the envelope technique with three-channel VI pick-up was employed to the data processing to analyze transient characteristics of vibration energy flow. Application limits of the present method near boundaries and on curved plates were clarified by experiments and by FEM simulation. Attempts were made to measure the vibration intensity on the practical mechanical structures within the application limits. Time-dependent multipath-transmissions of vibration energy were visualized successfully. It was shown that the application of the present technique can be informative in the diagnostics and control of noise and vibration in practical mechanical structures.