【正文】 ants are liquids(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。由它引起的熱能是一種浪費的能量。 在運動部件之間會發(fā)生很多摩擦，如 動摩擦。啟動摩擦通常都稍大于滑動摩擦。這個油膜使兩個表面分離，并且組織運動部件的兩個表面的相互潛入，以免產(chǎn)生熱量使兩表面膨脹，又引起更近的接觸。每一種潤滑劑都有其各自不同的功能和用途。并且以一種連續(xù)的固定的速度和數(shù)量。 在滑動面之間引入一層流體膜，把滑動表面完全隔離開，就產(chǎn)生了流體膜潤滑。 邊界潤滑 。 控制摩擦力 。適當(dāng)?shù)臐櫥瑒⒛軒椭朔鲜鎏岬降囊恍┠p現(xiàn)象。當(dāng)機器閑置不工作時，潤滑劑起到防腐劑的作用。 在象變壓器和配電裝置這些特殊用途中，具有很高介電常數(shù)的潤滑劑起電絕緣材料的作用。潤滑劑可以是任何一種物質(zhì)，這樣的物質(zhì)被填充到發(fā)生相對運動的兩個表面之間，實現(xiàn)這一目的。 （ 2） 流體膜潤滑。所以，這種潤滑也可以被叫做液體潤滑。 在有的軸承上，搖桿旋轉(zhuǎn)或在軸承上轉(zhuǎn)動，相對運動就是滑動。還有另一種極端的情況，在有些軸承有幾千種應(yīng)用，應(yīng)對各種不同的載荷。隨著對潤滑的研究的知識的積累，設(shè)計出有良好工作狀況和較高的穩(wěn)定性的軸承已不是很遙遠(yuǎn)了。有些有連接桿的軸承，比如說汽車發(fā)動機上的，必須在幾千度高的高溫下和各種不同性質(zhì)的載荷下工作。 當(dāng)軸承不得不在較高的溫度下工作的時候，固體潤滑劑例如合成物等，必須被使用，因為通常使用的潤滑油在這種情況下都不能工作。這種擠壓力是運動表面本身施加給潤滑劑而產(chǎn)生的，當(dāng)然這仍然是一種可能。有些人推斷，按這種理解，液體的這種化學(xué)合成是十分重要的，它們提出了這樣的詞“邊界潤滑”，邊界潤滑是和流體潤滑相對的另一種潤滑。 潤滑的目的就是為了，減小摩擦力，降低能量損耗，減少機器的熱量產(chǎn)生。 潤滑劑被廣泛用來作為液壓傳動中的工作液體。 控制腐蝕 。 磨損控制 。但潤滑劑不僅僅以脂肪、粉末和油脂這樣一些為人們所熟悉的形態(tài)出現(xiàn)，在一些精密的機器中，金屬也通常作為滑動面。如果潤滑膜中的壓力是由外源提供的，這種系統(tǒng)稱為流體靜壓潤滑。當(dāng)達不到這么高的純凈度時，吸附在表面的氣體、水蒸氣、氧化物和污染物就會降低摩擦力并減小粘附的趨勢，但通常會產(chǎn) 生9 嚴(yán)重的磨損，這種現(xiàn)象被稱為“無潤滑”摩擦或者叫做干摩擦。 在工業(yè)裝置中，常用的有一種潤滑系統(tǒng)是壓力系統(tǒng)。這種類型的軸承把它的潤滑劑帶到應(yīng)力最大的部位。 8 由運動部件的表面不平度的楔入作用引起的摩擦可以被部分的克服，那就需要靠兩表面之間的潤滑。一旦運動部件運動起來，便有了規(guī)律可循，滑動就可以實現(xiàn)這一點。如果因為膨脹導(dǎo)致了一個足夠大的積壓力，那么，這個軸承就可能會卡死或密封死。而摩擦這個詞，本身就意味著，兩個或 兩個以上部件的阻止相對運動趨勢。1 外文文獻 原文： Friction , Lubrication of Bearing In many of the problem thus far , the student has been asked to disregard or neglect friction . Actually , friction is present to some degree whenever two parts are in contact and move on each other. The term friction refers to the resistance of two or more parts to movement. Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener and the parts together. Belt drivers, brakes, and tires are additional applications where friction is necessary. The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. Also , greater power is required to overe the increased friction. Heat is destructive in that it causes expansion. Expansion may cause a bearing or sliding surface to fit tighter. If a great enough pressure builds up because made from low temperature materials may melt. There are three types of friction which must be overe in moving parts: (1)starting, (2)sliding, and(3)rolling. Starting friction is the friction between two solids that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. To produce motion in these parts, the wedgeshaped peaks and valleys of the stationary surfaces must be made