【正文】 e film that may contain additives to neutralize corrosive materials. The ability of a lubricant to control corrosion is directly relatly to the thickness of the lubricant film remaining on the metal surfaces and the chermical position of the lubricant. Other functions Lubrication are frequently used for purposes other than the reduction of friction. Some of these applications are described below. Power transmission. Lubricants are widely employed as hydraulic fluids in fluid transmission devices. 5 Insulation. In specialized applications such as transformers and switchgear , lubricants with high dielectric constants acts as electrical insulators. For maximum insulating properties, a lubricant must be kept free of contaminants and water. Shock dampening. Lubricants act as shockdampening fluids in energy transferring devices such as shock absorbers and around machine parts such as gears that are subjected to high intermittent loads. Sealing. Lubricating grease frequently performs the special function of forming a seal to retain lubricants or to exclude contaminants. The object of lubrication is to reduce friction ,wear , and heating of machine pars which move relative to each other. A lubricant is any substance which, when inserted between the moving surfaces, acplishes these purposes. Most lubricants 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。 1 廣西 大學 畢業(yè)設(shè)計（論文）外文翻譯 畢業(yè)設(shè)計（論文）題目： 外文題目： Friction , Lubrication of Bearing 譯文題目： 軸承的摩擦與潤滑 系 別 ： 機 械 工 程 系 專 業(yè)： 機械工程制造及其自動化 班 級： 學 號： 姓 名： 指導教師： 2021 年 03 月 03 日 2 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, t