U/i证2 sion [k' 在较小的 lesen ['n] ,减少，挥小，减 [zv:tiv】]a.保存的，将约 dditive aditiv] neutralize 'niutroniz 。使中和，使中立 provisio [v 几，（模防）搭保 Notes 1In the absence of such a high degree of cleanliness,absorbed gases.water vapour,oxides,and contaminants roduce friction and the tendency to seize but usually result in severe wear:this is called "unlubricated"or dry 若没有在表面达到这样高的清洁度，被吸附在接触表面的气体，水蒸气，氧化 that the within the 润滑油膜内的压力必领与作用于相对滑移表面上的载荷平衡才能使两部分 分离 3.They reduce abrasive and solid-to-solid contact wear by providing a film that increases the distance between the sliding surfaces,thereby lessening the damage by abrasive contaminants and surface asperities. 滑剂在相对滑移表面形成油膜，增加了两表面间的距离，从而轻了擦伤 固体与固体接触而形成的磨损，这样降低了有研磨作用的杂质和表面四凸不 对表面的损害 Exercises okd cun te c
2.Thereare sv kinds,theye Unlubricatod sliding is also called sliding 4In fluid-film lubrication although the fluid is usually a liquid such as and a wide range of other materials,it may also bea 5.To keep the parts separated.it is ncosary that the presure within the lubricating film the ld on the sliding suraces. d-i m lubrication depends upon the a significant portion of lubrication onl nd stopping of machines 8.Lubricants perform numerous other functions,such as control. ontrol.tempcrature control and control. 9.The roke of a lubricant in controlling corrosion of the surfaces themselves is 10.Lubricants are frequently used for purpoes other than the reductionof 1.unlubricated sliding 2.fluid-film lubrication 3.boundary lubrication 4.solid lubrication 5.friction contro 6.wear contro 日
Uni证2 Read More Application of Labricants by hand,but morn machinery rent metho of lubrication and types s of lubricants must be emploved for different parts.In an automobile.for example,the chassis is lubricated with grease,the manual transmission and rear-axke housings are filled with heavy oil.the automatic transmission is lubricated with special-grade light oil,wheel bearings are packed with gres that has a thickener composed of long fibers,and the crankcasc oil that lubricates engine parts is a lightweight.free-flowing oil Application of Liquid Lubricants Mechanical devices to sply lubricantsar called lubricators.Asimpl inst them they feed oil hu cnillry action Horizontal bearings are froquently piled by a rotating ring or chain that carric oil from a reservoir in the bearing housing and distributes it along the bearing through grooves or channels.Bath oiline is useful where an oil-tight reservoi can be provided in which the bearing joural may be submerged.the pool of oil helps to carry away heat from contact surfaces. Splash-oiling deviccs arc us where gears in hot sings have mo ing part that dip into the .and s of a parts of the system.Many
o ate oil resecr or in an external tank.In an automobile engine a gear pump delivers the oil at low pressure to the bearings.Some bearings may depend on oil splashed from the bottom of the crankease by the turning crankshaft.In a two-stroke engine the lubricating oil is mixcd with the fucl. Application of Semisolid and Solid Lubricants Grease lubricants are semisolid and have several important advantages They resist being squeezed out,they are useful under heavy load conditions and in inaccessible parts where the supply of lubricant cannot easily be renewed, and they tend to form a crust that prevents the entry of dirt or grit between contact rfes.Grease isa mixture of a lubricant and a thickener;often it is made from a mineral oil and a soap.It may be applied in varous ways:by adjcent well.by forcing it through greasc cups by apring device,and b Other Applications Lubricants are for puposs other than the reduction of friction.Som of thesc app ons are oc lubricants with high dielectric electrical insulators.For maximum propertis,ricant must be kept free of contaminant and water
Unit2 hine parts performs the spocial function of (661 words) Words and Expressions ,底 wick [wik] ,蜡桂心，灯芯 n. oiler ['alb] capillry [ka inermittent[ito以：'mitort] sealing ['selin inultion[i时rdml,绝线，船热，施 switchgcar [it] ，开关装置配电 exclucke [iks'klur ,拒地，非除，秘地 装置