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Volume 18 - Friction, Lubrication, and Wear Technology Part 7

Tham khảo tài liệu 'volume 18 - friction, lubrication, and wear technology part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | discussion the difference between RCW and RCF is that in RCF surface fatigue is the damage accumulation process that eventually results in wear particle formation. Rolling contact fatigue may continue for hundreds thousands or even millions of cycles before the first wear particles are removed. Furthermore the corners of pits or other RCW damage features may act as nucleation sites for additional fatigue cracks and spread the damage across the surface. Because RCF and RCW are so closely related the causes and effects of both processes will be discussed. The magnitude of the effects of RCW varies from one tribosystem to another. Sometimes a component can sustain appreciable RCW damage before its function is impaired other times loss of performance immediately results from the first spall. For example a guide roller in a hot metal bar-handling system may sustain considerable RCW but this wear may be unimportant as long as the component continues to function adequately. In the case of ultraprecision ball bearings for missile guidance systems however a very small spall may cause the center of mass of the rapidly spinning bearing to shift resulting in significant guidance errors. Rolling contact is frequently accompanied by slip or sliding. The complex motions experienced by tribocomponents in many types of rolling contact situations produce at least a small percentage of slip or sliding. Pure rolling is probably the exception rather than the rule in the diverse applications of rolling components. For example Fig. 1 is a schematic profile of meshing spur gears. When the gear teeth first touch there is a measure of sliding plus rolling. When the contact point coincides with the pitch circle there is pure or nearly pure rolling depending on the accuracy of gear alignment or lateral vibration . Past this point slip again occurs between tooth surfaces it reaches its second maximum just at the point where the surfaces separate. Slip can result in scuffing or adhesive wear .