Study on Vibration and Noise Reduction Induced by Friction Force

本文研究弹性结构表面摩擦引起的振动和噪声的降低。众所周知，摩擦力会在动力系统中诱发自激振动，这是由于系统的表观负阻尼引起的。一旦发生这种情况，很难降低振动的振幅，有时会导致系统本身的破坏。在系统没有受到破坏的情况下，摩擦振动会产生很大的噪声，使周围的人感到不舒服，因此研究摩擦振动的机理，降低其振幅和噪声是非常重要的，自激振动和粘滑现象是本文研究的主要对象。虽然粘滑现象通常被认为是自激振动，但它们是不同的。粘滑现象是由静摩擦力和动摩擦力的差异引起的。另一方面，自激振动被定义为由振动的负阻尼引起的。 ...更多信息 系统在具有等效负阻尼的动力学系统中，有时会出现粘滑现象，这可能会引起混淆，为了避免粘滑现象，有效的方法之一是减小静、动摩擦力之差。自动变速器油（ATF）就是为此目的而开发的，它混合了各种摩擦改进剂（FM）。即使将FM应用于有可能表现出粘滑现象的系统，在长时间间隔后也可能恶化。当噪声主要是由摩擦片的面外振动引起时，减小摩擦面到摩擦片中性面的距离可能是降低噪声的有效方法。最佳条件是两个平面重合。本试验是在小尺寸模型上进行的，结果表明摩擦片的振幅有明显的减小。但应该注意的是，振动能量被传递到系统的其他弹性部件，并且噪声由系统的其他部分产生。磁流变液作为一种功能流体，已成功地应用于可控阻尼器中。研究者建议设计MR器械时考虑MR流体在机械组件中的流动模式。如上所述，减少振动和噪音的最佳方法之一是将阻尼器应用于摩擦系统，但在不久的将来可能会对该系统进行实验验证。少

This research deals with the vibration and noise reduction induced by the friction between surfaces of elastic structures. It is well known that the friction force may induce self-excited vibration in dynamic systems caused by the apparent negative damping of the system. Once it happens, it is very difficult to reduce the amplitude of vibration and it is sometimes followed by the destruction of the system itself. In the case when there is no destruction of the system, it makes large noise uncomfortable for the people around it. So it is important to study the mechanism of friction vibration to reduce its amplitude and noise.Self-excited vibration and stick-slip phenomena are main target of this study. Though stick-slip phenomenon is usually considered as self-excited vibration, they differ to each other. Stick-slip is typically caused by the difference of static friction force and dynamic one. On the other hand, self-excited vibration is defined to be caused by negative damping of the … More system. It may be confusing that stick-slip phenomena are sometimes found in the dynamic system having equivalent negative damping.In order to avoid the stick-slip phenomena, one of the effective ways is to decrease the difference between the static and dynamic friction force. Automatic Transmission Fluid (ATF) has been developed for this purpose and various kinds of Friction Modifier (FM) are blended. Even applying FM to the system which has the possibility to show the stick-slip phenomena, it may be deteriorated after long interval. When the noise is caused mainly by the out-of-plane vibration of friction plates, it may be effective for noise reduction that the distance from the friction surface to the neutral plane of the plate should be decreased. The best condition is coinciding the two planes each other. This trial was conducted by small size model, and it showed remarkable decrement of amplitude of the friction plates. But it should be noted that the vibration energy was transmitted to the other elastic components of the system, and noise was made by other part of the system. In such cases, the vibration amplitude should be decreased by absorbers.MR fluid is one of the functional fluids, and it has been successfully applied to controllable dampers. The investigators proposed to design MR devices considering the flow patterns of MR fluid in the mechanical components. As described above, one of the best ways for vibration and noise reduction is to apply dampers to the friction system, but the experimental verification of this idea to the system may be conducted in the near future. Less