tailieunhanh - Mechanical Engineering-Tribology In Machine Design Episode 2

Tham khảo tài liệu 'mechanical engineering-tribology in machine design episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 12 Tribology in machine design additives are generally satisfactory under high-torque low-speed conditions but are sometimes less so at high speeds. The prevailing modes of failure are pitting and scuffing. . Worm gears Worm gears are somewhat special because of the degree of conformity which is greater than in any other type of gear. It can be classified as a screw pair within the family of lower pairs. However it represents a fairly critical situation in view of the very high degree of relative sliding. From the wear point of view the only suitable combination of materials is phosphor-bronze with hardened steel. Also essential is a good surface finish and accurate rigid positioning. Lubricants used to lubricate a worm gear usually contain surface active additives and the prevailing mode of lubrication is mixed or boundary lubrication. Therefore the wear is mild and probably corrosive as a result of the action of boundary lubricants. It clearly follows from the discussion presented above that the engineer responsible for the tribological aspect of design be it bearings or other systems involving moving parts must be expected to be able to analyse the situation with which he is confronted and bring to bear the appropriate knowledge for its solution. He must reasonably expect the information to be presented to him in such a form that he is able to see it in relation to other aspects of the subject and to assess its relevant to his own system. Furthermore it is obvious that a correct appreciation of a tribological situation requires a high degree of scientific sophistication but the same can also be said of many other aspects of modern engineering. The inclusion of the basic principles of tribology as well as tribodesign within an engineering design course generally does not place too great an additional burden on students because it should call for the basic principles of the material which is required in any engineering course. For example a study of the .