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1、第第 2 次课的教学整体安排次课的教学整体安排 授课时间第 2 周 周 4 第 3、4 节课时安排2 授课题目(教学章、节或主题)： Lubrication 教学目的、要求（分掌握、理解、了解三个层次）： 掌握本课的专业词汇 学习并掌握专业英语的翻译技巧 教学内容（包括基本内容、重点、难点）： Lubrication Varieties of lubrication; Functions of lubricants; Other functions 讲解课文和专业词汇 重点：在翻译的过程中句子表达的准确性和整篇文章的逻辑性。 难点：在科技英语翻译过程中语言的转换技巧 讨论、思考、作业： 作业：
2、复习课文 背诵专业词汇 参考资料（含参考书、文献等）： 教学过程设计：复习 10 分钟，授新课 90 分钟，安排讨论 分钟，布置作业 分钟 授课类型： 理论课 讨论课 实验课 练习课 其他 教学方式： 讲授 讨论 指导 其他 教学资源： 多媒体 模型 实物 挂图 音像 其他 填写说明：1.每项页面大小可自行添减； 2.教学内容与讨论、思考题、作业部分可合二为一。 2 Lubrication 润润 滑滑 Although one of the main purposes of lubrication is to reduce friction, any substance liquid, sol
3、id, or gaseouscapable of controlling friction and wear between sliding surfaces(滑动表面) can be classed as (定义为)a lubricant. Varieties of lubrication Unlubricated(无润滑无润滑) sliding. Metals that have been carefully treated to remove all foreign materials(异物) seize and weld to one another when slid togethe
4、r. In the absence of(如果没有) such a high degree of cleanliness, adsorbed(吸附的) gases, water vapor, oxides(氧化物), and contaminants (杂 质)reduce friction and the tendency to seize but usually result in severe wear, this is called “unlubricated” or dry sliding (干滑动). Fluid-film(流体膜流体膜) lubrication. Interpos
5、ing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. The fluid may be introduced intentionally as the oil in the main bearing(主轴承) of an automobile, or unintentionally, as in the case of water between a smooth rubber tire(橡胶轮胎) and a wet pavement(路面). Al
6、though 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 commonly employed is air. To keep the parts separated, it is necessary that the pressure within the lubrication film balance(与保持平衡) the load on the sliding surfaces. If th
7、e lubricating films pressure is supplied by an external source, the system is said to be lubricated hydro-statically(静压地). If the pressure between the surfaces is generated as a result of the shape and motion of the surfaces themselves, however, the system is hydro-dynamically(动压地) lubricated. This
8、second type of lubrication depends upon the viscous properties(粘度特性) of the lubricant. Boundary lubrication. A condition that lies between unlubricated sliding and fluid film lubrication is referred to as(称作) boundary lubrication, also defined as that condition of lubrication in which the friction b
9、etween surfaces is determined by the properties of the surfaces and properties of the lubricant other than viscosity(粘度). Boundary lubrication encompasses(包含) a significant portion of lubrication phenomena(润滑现象) and commonly occurs during the starting and stopping of machines. Solid lubrication. Sol
10、ids such as graphite(石墨) and molybdenum disulfide(二硫化钼) 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; even some metals commonly serve as sliding surfaces
11、in some sophisticated(精密的) machines. Functions of lubricants Although a lubricant primarily controls frictions and wear, it can and ordinarily does perform numerous other functions, which vary with the application and usually are interrelated. Friction control. The amount and character of the lubric
12、ant made available to sliding surfaces have a profound effect upon the friction that is encountered. For example, disregarding such related factors as heat and wear but considering friction alone between two oil-film lubricated surfaces, the friction can be 200 times less than that between the same
13、surfaces with no lubricant. Under fluid-film conditions, friction is directly proportional to(与 成正比) the viscosity of the fluid. Some lubricant, such as petroleum derivatives(衍生物), is available in a great range of viscosities(具有较大的粘度 范围) and thus can be satisfy a broad spectrum of functional require
14、ments. Under boundary lubrication conditions, the effect of viscosity on friction becomes less significant than the chemical nature(化学性质) of the lubricant. Wear control. Wear occurs on lubricated surfaces by abrasion(磨蚀), corrosion, and solid to-solid contact. Proper lubricants will help combat(克服)
15、each type. 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 surfaces asperities(粗糙 不平). Temperature control. Lubricants assist in controlling temperature by red
16、ucing friction and carrying off(带走) the heat that is generated. Effectiveness(效果) depends upon the amount of lubricant supplied, the ambient temperature, and the provision for external cooling. To a lesser extent(在小范围内), the type of lubricant also affects surface temperature. Corrosion control. The role of lubricants in controlling corrosion of the surfaces themselves is twofold(双重的). When machinery is idle(闲置), the lubricants act as a preservative(防锈剂). When machinery is i
