完整版王宝帅机械类外文文献翻译毕业设计论文文档格式.docx

1、 毕业设计（论文）外文翻译毕业设计（论文）题目： 工具盒盖注塑模具设计 外文题目： Friction , Lubrication of Bearing 译文题目： 轴承的摩擦与润滑 系 （部）： 机 械 系 专业班级：机械设计制造及其自动化0801学生姓名： 王宝帅 指导教师： 魏晓波 2010年 10 月 15 日外文文献原文： Friction , Lubrication of BearingIn many of the problem thus far , the student asked to disregard or neglect friction . Actually , fr

2、iction 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 where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to is n

3、ecessary.The friction of moving parts in a machine is is lost energy because no work takes place. Also , greater power is required to overcome 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 p

4、ressure builds up because made from low temperature materials may melt.There are three types of friction which must be overcome 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

5、 rest, the surface irregularities of both parts tend to interlock and form a wedging action. To produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. The rougher the two surfaces, the greater is starting friction r

6、esulting from their movement .Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other. The friction of the two surfaces is known as sliding friction. As shown in figure ,star

7、ting friction is always greater than sliding friction .Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphi

8、ll. This changing of shape , known as deformation, causes a movement of molecules. As a result ,.The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces. However, even these smooth surfaces may require the use of a substan

9、ce between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing is to use different materials for the bearing s

10、urfaces and rotating parts. This explains why bronze bearings, soft alloys, and copper and tin iolite bearings are used with both soft and the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its own lubricant to the points wh

11、ere the pressures are the greatest.Moving parts are lubricated to reduce friction, wear, and slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other .A second common method of lubrication

12、is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the piston.A lubrication

13、 system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity.There are numerous other systems of lubrication and a considerable number of lubricants available for any given

14、set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices.Although one of the main purposes of lubrication is reduce friction, any sub

15、stance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant. Varieties of lubricationUnlubricated sliding. Metals that carefully treated to remove all foreign materials seize and weld to one another when slid together. In the abs

16、ence of such a and the tendency to seize but usually result in severe wear; this is called “unlubricated ”or dry sliding.Fluid-film lubrication. Interposing 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 of an automobile, or unintentionally, as in the