Machined Brass and Pressed Steel Bearing （机加工黄铜和钢轴承）.pdf

MACHINED BRASS AND PRESSED STEEL BEARING CAGES: A COMPARATIVE STUDY RKB TECHNICAL REVIEW - JULY 2011 Machined Brass and Pressed Steel Bearing Cages: a Comparative Study Spiridon CRETU RKB Bearing Industries – Engineering and Research Department Abstract: The international standards ISO 281:2007 and ISO 16281:2008 estimate bearings basic dynamic rating loads and basic rating lives on the basis of subsurface contact fatigue of raceways. A life modification factor, aISO, is further considered in these standards to include surface originated fatigue and correspondingly to evaluate the modified rating lives, but with any implication of cage design and material (brass or steel). Anyway, statistics reveal that only a small percentage of bearing failures is due to subsurface fatigue. Fluctuations in cage speed generate high forces of inertia and skewing motion alters roller- cage contact to the harmful edge contact. These effects give rise to considerable pressure between cage contacting surfaces, that, for rolling bearings equipped with steel cages and operating in conditions of poor lubrication, may lead to adhesive wear and smearing. The hard steel contaminants that may appear, as well as the indentations that may form on raceways and rolling elements, act as locations for surface fatigue, causing a much shorter life than that calculated using ISO 28 1:2007. In such cases bearings