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

在确定机器噪声控制的有效方法时，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出去。噪声源并不总是与结构中的激振点重合。因此，识别激励源和振动能量传递路径可以为噪声和振动控制措施提供决定性的信息。振动强度(VI)技术被认为对这一目的很有用。VI是单位宽度在给定方向上的振动功率。将这种强度法应用于实际机械结构的诊断存在一定的困难。从不同测点测得的一组振动数据计算三阶导数可能会产生误差。此外，由于时间平均过程，通常在大多数实际结构中观察到的振动能量流的瞬时特征被丢失。本研究的目的是开发一种适用于实际机械结构中VI测量的简化测量技术。本文将三通道VI拾取的包络技术应用到数据处理中，分析了振动能流的暂态特性。通过实验和有限元模拟，明确了该方法在边界附近和曲板上的应用范围。对实际机械结构在使用范围内的振动强度进行了测量。成功地模拟了振动能量随时间变化的多径传输过程。结果表明，该技术的应用对实际机械结构的噪声和振动的诊断和控制具有一定的参考价值。

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.