Near Frictionless Surface Acoustic Wave Active Bearing for Disk Drive and Other Applications

本研究探讨一种利用表面声波（SAW）进行润滑的新型机械界面。在这个概念中，SAW？S用于实现在以高相对速度滑动的两个表面之间具有零有效摩擦的直接接触界面。如果在两个表面中的一个表面上激发行进SAW，并且作为行进SAW的峰值的接触点具有与两个表面之间的相对速度相同的水平速度，则接触点将不会经历任何摩擦。零滑动速度接触点的产生最大限度地减少了有效摩擦，而无需使用任何润滑剂，因此可以实现许多新的应用。 这是匡威的效果，超声波电机，其中使用SAW？在两个表面之间产生摩擦力。本研究的主要目的是对声表面波的动力学特性有一个新的认识。及其对界面摩擦学性能的影响。这些新的认识有望带来革命性的新技术，用于抑制运动表面之间的摩擦和磨损。在这项研究中，定制的实验装置被用来研究SAW的各种复杂的几何形状，如声换能器，波导，耦合器等的动态也，各种相互作用的声场与材料进行了研究。这些研究将为SAW动力学、各种应用的功能声学元件设计和弹性材料的动力学/摩擦学特性带来新的基础知识。虽然作为一种新型轴承的一般应用显然很重要，但这种新技术可能会带来一些特定的应用。其中最突出的例子是硬盘驱动器（HDD）。在HDD中，读取和写入数据的磁头在由空气轴承支撑的旋转磁盘上方飞行。需要有限的间隔来防止磁头和磁盘之间的摩擦和磨损。同时，为了良好的写入效率和读取灵敏度，间隔必须尽可能小，因为磁场随着间隔的增加而呈指数衰减。为了满足未来的数据存储需求，有必要将这种间距减小到5 nm，这是一个巨大的挑战，因为在这些距离上控制磁头高度和防止接触是困难的。此外，用于空气轴承技术的空气流的产生消耗HDD中的显著功率，并且HDD是IT基础设施中的总功率消耗的显著部分。它们的耗电量占美国总用电量的1.5%（2006年，EPA）。拟议的概念提供了一种新的革命性手段，可以零摩擦地将头连接到磁盘，以实现更高的记录密度，并且还可以使硬盘驱动器在降低的内部气压下运行，这将显着降低硬盘驱动器的功耗。

This research investigates a novel mechanical interface which utilizes surface acoustic waves (SAW) for lubrication. In this concept, SAW?s are used to realize a direct contact interface with zero effective friction between two surfaces sliding at high relative velocities. If a traveling SAW is excited on one of the two surfaces moving relative to one another, and the contact points, which are the peaks of the traveling SAW, have the same horizontal velocity as the relative velocity between the two surfaces, the contact points will not experience any friction. The creation of zero-sliding-velocity contact points minimizes effective friction without applying any lubricants and, as a result, enables a host of new applications. This is the converse effect to ultrasonic motors, which use SAW?s to create friction forces between two surfaces. This concept in essence is an active mechanical bearing.The main objective of this research is to gain new understanding about the dynamics of SAW?s and their effects on the tribological properties at interfaces. These new understandings are expected to lead to revolutionary new techniques for suppressing friction and wear between moving surfaces. In this research, custom experimental apparatuses are used to study the dynamics of SAW on various complex geometries, such as acoustic transducers, wave guides, couplers, etc. Also, various interactions of the acoustic field with materials are studied. These studies should lead to fundamental new knowledge about SAW dynamics, functional acoustic component design for various applications and dynamical/tribological properties of elastic materials.While general applications as a new form of bearing are obviously important, there are several specific applications that may be enabled by such a new technology. One of the most striking examples is in the hard disc drive (HDD). In a HDD, a magnetic head, which reads and writes data, flies above a rotating magnetic disc supported by an air bearing. A finite separation is needed to prevent friction and wear between the head and the disc. At the same time, the separation has to be as small as possible for good write efficiency and read sensitivity, because the magnetic fields decay exponentially with increasing separation. To meet future data storage needs it is necessary to reduce this separation to 5nm, an immense challenge since controlling the head height and preventing contact is difficult at these distances. Moreover, the creation of air flow for the air bearing technique consumes significant power in HDDs, and HDDs are a significant portion of the total power consumption in the IT infrastructure. Their power consumption accounts for 1.5% of the total electricity usage in US (2006, EPA). The proposed concept provides a new, revolutionary means to couple the head to the disc with zero friction to achieve higher recording density, and also has the possibility for a HDD to operate with reduced internal air pressure, which should significantly reduce HDD power consumption.