機(jī)械類畢業(yè)設(shè)計(jì)外文翻譯---軸承的摩擦與潤(rùn)滑-預(yù)覽頁(yè)
【正文】 iquids(such as mineral oil, silicone fluids, and water),but they may be solid for use in dry bearings, greases for use in rolling element bearing, or gases(such as air) for use in gas bearings. The physical and chemical interaction between the lubricant and lubricating surfaces must be understood in order to provide the machine elements with satisfactory life. The understanding of boundary lubrication is normally attributed to hardy and doubleday , who found the extrememly thin films adhering to surfaces were often sufficient to assist relative sliding. They concluded that under such circumstances the chemical position of fluid is important, and they introduced the term “boundary lubrication”. Boundary lubrication is at the opposite end of the spectrum from hydrodynamic lubrication. Five distinct of forms of lubrication that may be defined :(a) hydrodynamic。 this is called “unlubricated ”or dry sliding. Fluidfilm lubrication. Interposing a fluid film that pletely separates the sliding surfaces results in fluidfilm lubrication. The fluid may be introduced intentionally as the oil in the main bearing of an automobile, or unintentionally, as in the case of water between a smooth tuber tire and a wet pavement. Although the fluid is usually a liquid such as oil, water, and a wide range of other materials, it may also be a gas. The gas most monly employed is air. Boundary lubrication. A condition that lies between unlubricated sliding and fluidfilm lubrication is referred to as boundary lubrication, also defined as that condition of lubrication in which the friction between surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity. Boundary lubrication enpasses a significant portion of lubrication phenomena and monly occurs during the starting and stopping off machines. Solid lubrication. Solid such as graphite and molybdenum disulfide are widely used when normal lubricants do not possess sufficient resistance to load or temperature extremes. But lubricants need not take only such familiar forms as fats, powders, and gases。 (e)solid film. Hydrodynamic lubrication means that the loadcarrying surfaces of the bearing are separated by a relatively thick film of lubricant, so as to prevent metal contact, and that the stability thus obtained can be explained by the laws of the lubricant under pressure ,though it may be。 在一個(gè)機(jī)器中，運(yùn)動(dòng)部件的摩擦是有害的，因?yàn)樗档土藱C(jī)械對(duì)能量的充分利用。熱能是有破壞性的。另外，隨著溫度的升高，如果不是耐高溫材料制造的軸承，就可能會(huì)損壞甚至融化。這些靜止部件的凹谷和尖峰必須整理光滑，而且能相互抵消。兩個(gè)運(yùn)動(dòng)部件之間的摩擦就叫做滑動(dòng)摩擦?？梢允狗肿舆\(yùn)動(dòng)。但是，即使是非常光滑的兩個(gè)表面之間也可能需要一種物質(zhì)，這種物質(zhì)就是通常所說(shuō)的潤(rùn)滑劑，它可以提供一個(gè)比較好的、比較薄的油 膜。也就是說(shuō)用軟的或硬的金屬組成表面。 對(duì)運(yùn)動(dòng)部件潤(rùn)滑以減小摩擦，應(yīng)力和熱量，最常用的是油、脂、還有合成劑。 在低速度運(yùn)動(dòng)的部件，一個(gè)油溝足以將所需要的數(shù)量的潤(rùn)滑劑送到相互運(yùn)動(dòng)的表面。這種系統(tǒng)中，一個(gè)機(jī)器上的一個(gè)泵，可以將潤(rùn)滑劑帶到所有的軸承表面。 盡管潤(rùn)滑的主要目的之一是為了減小摩擦力，任何可以控制兩個(gè)滑動(dòng)表面之間摩擦和磨損的物質(zhì)，不管是液體還是固體或氣體，都可以歸類于潤(rùn)滑劑。 流體膜潤(rùn)滑 。盡管流體通常是油、水和其他很多種類的液體，它可以是氣體。如果滑動(dòng)表面之間的壓力是由于滑動(dòng)面本身的形狀和運(yùn) 動(dòng)所共同產(chǎn)生的，這種系統(tǒng)就稱為流體動(dòng)壓力潤(rùn)滑。邊界潤(rùn)滑包括大部分潤(rùn)滑現(xiàn)象，通常在機(jī)器的啟動(dòng)和停止時(shí)出現(xiàn)。 潤(rùn)滑劑的作用 盡管潤(rùn)滑劑主要是用來(lái)控制摩擦和磨損的，它們能夠而且通常也確實(shí)起到許多其他的作用，這些作用隨其用途不同而不同，但通常相互之間是有關(guān)系的。在流體潤(rùn)滑狀況時(shí)，摩擦力與流體黏度成正比。 磨蝕、腐蝕與固體和固體之間的接觸就會(huì)造成磨損。 潤(rùn)滑劑通過(guò)減小摩擦和將產(chǎn)生的熱量帶走來(lái)降低溫度。 潤(rùn)滑劑在控制表面腐蝕方面有雙重作用。 其他作用 除了減小摩擦外，潤(rùn)滑劑還經(jīng)常有其他的用途。 絕緣 。 在象減振器這樣的能量傳遞裝置中 和在承受很高的間隙載荷的齒輪這樣的機(jī)器零件的周圍，潤(rùn)滑劑被作為減振液使用。熱量就是因?yàn)楸砻娴南嗷ラg的相對(duì)運(yùn)動(dòng)造成的。在 潤(rùn)滑劑和潤(rùn)滑表面之間這種化學(xué)的和物質(zhì)的相互滲入作用，就是為了提供給機(jī)器一個(gè)良好的工作狀態(tài)。 關(guān)于潤(rùn)滑的五種不同的潤(rùn)滑形式主要有： 11 （ 1） 無(wú)潤(rùn)滑潤(rùn)滑劑。 （ 5） 固體潤(rùn)滑。這種由運(yùn)動(dòng)表面產(chǎn)生的擠壓力產(chǎn)生了必要的壓力來(lái)分隔工作表面來(lái)抵抗加在軸承上的載荷。 第三種潤(rùn)滑方式是一種現(xiàn)象，這種現(xiàn)象是，一種潤(rùn)滑劑是用在發(fā)生相對(duì)轉(zhuǎn)動(dòng)的工作表面之間。目前，在這方面的研究正在實(shí)施，為了尋找到合成軸承的材料，并且有低損耗和小的熱量產(chǎn)生的性能。齒輪的齒嚙合是轉(zhuǎn)動(dòng)與相對(duì)滑動(dòng)的合成。這種軸承用在汽輪發(fā)動(dòng)設(shè)備上可以說(shuō)是穩(wěn)定性接近 100%。需要很少的甚至是12 不需要 潤(rùn)滑劑。
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