机械工程专业英语1-14章.ppt

上一课回顾 单词复习： Shaft Coupling Clutches Spring Rigid coupling Flexible coupling Hydraulic 齿轮 机床 曲柄 振动 Lesson 2 Lubrication润滑 重点词汇： gaseous/gas/liquid/solid interpose/pavement portion, sophisticated, interrelate, available, proportional, combat, assist, twofold Paragraph 1 Although one of the main purposes of lubrication is to reduce friction, any substance –liquid, solid, or gaseous—capable of controlling friction and wear between sliding surfaces(滑动表面) can be classed as (定义为)a lubricant. 尽管润滑的主要目的之一是为了减少摩擦力，任何可以控制两滑动表面之间的摩擦和磨损(wear) 的物质——不管是液体、固体或者气体，都可以归类为(be classed as)润滑剂。 Varieties of lubrication Paragraph 2: Unlubricated(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 together. 经过精心处理去除了所有杂质(foreign material)的金属在相互滑动时，会粘附(seize)或熔接(weld)到一起. 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). 当达不到高的清洁度(cleanliness)时，吸附在表面的气体、水蒸汽、氧化物(oxide)和污染物会降低摩擦力并减少黏附的趋势，但通常会产生严重的磨损，这种现象被称为“无润滑”摩擦或干摩擦(dry sliding)。 Paragraph 3: Fluid-film(流体膜) lubrication. Interposing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. 在滑动面之间引入一层流体膜，把润滑表面完全隔离开，就产生了（result in）流体膜润滑。 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). 这种流体可能是有意引入的，例如汽车主轴承中的润滑油；也可能是无意中引入的，例如在光滑的橡胶轮胎与潮湿的路面pavement之间的水。 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 commonly employed is air. 尽管流体通常是油、水和很多其它种类的液体，也可以是气体，最常用的气体是空气。 Paragraph 4: To keep the parts separated, it is necessary that the pressure within the lubrication