Study on Vibration and Noise Reduction Induced by Friction Force

本文研究了弹性结构表面间摩擦引起的减振降噪问题。众所周知，在动力系统中，由于系统的表观负阻尼，摩擦力会引起自激振动。一旦发生这种情况，就很难减小振动幅度，有时还会导致系统本身的破坏。在没有破坏系统的情况下，它会使周围的人感到不舒服。因此，研究摩擦振动的机理对减小摩擦振动的振幅和噪声具有重要意义。自激振动和粘滑现象是本研究的主要对象。粘滑现象通常被认为是自激振动，但两者是不同的。粘滑通常是由静摩擦力与动摩擦力的差异引起的。另一方面，自激振动被定义为由…More系统的负阻尼引起的。具有等效负阻尼的动力系统有时也会出现粘滑现象，这可能令人困惑。为了避免粘滑现象的发生，减小静、动摩擦力差是有效的方法之一。为此研制了自动变速箱油（ATF），并混合了各种摩擦改进剂（FM）。即使对有可能出现粘滑现象的系统应用调频，也可能在较长时间间隔后出现劣化。当噪声主要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有效的降噪方法。最好的情况是两个平面相交。在小尺寸模型上进行了试验，结果表明摩擦板的振幅有明显的衰减。但需要注意的是，振动能量被传递给了系统的其他弹性部件，噪声是由系统的其他部分产生的。在这种情况下，应通过减振器减小振动幅度。磁流变液是一种功能流体，已成功应用于可控阻尼器。研究人员建议设计考虑磁流变液在机械部件中的流动模式的磁流变装置。如上所述，减少振动和噪声的最佳方法之一是在摩擦系统中应用阻尼器，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