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Sổ tay tiêu chuẩn thiết kế máy P30

Tham khảo tài liệu 'sổ tay tiêu chuẩn thiết kế máy p30', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 25 LUBRICATION A. R. Lansdown M.Sc. Ph.D. Director Swansea Tribology Centre University College of Swansea Swansea United Kingdom 25.1 FUNCTIONS AND TYPES OF LUBRICANT I 25.1 25.2 SELECTION OF LUBRICANT TYPE 25.2 25.3 LIQUID LUBRICANTS PRINCIPLES AND REQUIREMENTS 25.3 25.4 LUBRICANT VISCOSITY 25.6 25.5 BOUNDARY LUBRICATION 25.9 25.6 DETERIORATION PROBLEMS 25.12 25.7 SELECTING THE OIL TYPE 25.14 25.8 LUBRICATING GREASES I 25.17 25.9 SOLID LUBRICANTS 25.22 25.10 GAS LUBRICATION I 25.26 25.11 LUBRICANT FEED SYSTEMS 25.26 25.12 LUBRICANT STORAGE 25.29 REFERENCES 25.30 25.1 FUNCTIONS AND TYPES OF LUBRICANT Whenever relative movement takes place between two surfaces in contact there will be resistance to movement. This resistance is called the frictional force or simply friction. Where this situation exists it is often desirable to reduce control or modify the friction. Broadly speaking any process by which the friction in a moving contact is reduced may be described as lubrication. Traditionally this description has presented no problems. Friction reduction was obtained by introducing a solid or liquid material called a lubricant into the contact so that the surfaces in relative motion were separated by a film of the lubricant. Lubricants consisted of a relatively few types of material such as natural or mineral oils graphite molybdenum disulfide and talc and the relationship between lubricants and the process of lubrication was clear and unambiguous. Recent technological developments have confused this previously clear picture. Friction reduction may now be provided by liquids solids or gases or by physical or chemical modification of the surfaces themselves. Alternatively the sliding components may be manufactured from a material which is itself designed to reduce friction or within which a lubricant has been uniformly or nonuniformly dispersed. Such systems are sometimes described as unlubricated but this is clearly a matter of terminology. The system may be .