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타이틀	Interference-Fit Life Factors for Ball Bearings
저자	Oswald, Fred B.;; Zaretsky, Erwin V.;; Poplawski, Joseph V.
Keyword	BALL BEARINGS;; EXPONENTS;; FATIGUE LIFE;; GROOVES;; INTERFERENCE FIT;; LOADS (FORCES); SHEAR STRESS;; STRESSES
URL	http://hdl.handle.net/2060/20110000529
보고서번호	NASA/TM-2010-216913
발행년도	2010
출처	NTRS (NASA Technical Report Server)
ABSTRACT	The effect of hoop stresses on the rolling-element fatigue life of angular-contact and deep-groove ball bearings was determined for common inner-ring interference fits at the ABEC-5 tolerance level. The analysis was applied to over 1150 bearing configurations and load cases. Hoop stresses were superimposed on the Hertzian principal stresses created by the applied bearing load to calculate the inner-race maximum shearing stress. The resulting fatigue life of the bearing was recalculated through a series of equations. The reduction in the fatigue life is presented as life factors that are applied to the unfactored bearing life. The life factors found in this study ranged from 1.00 (no life reduction)where there was no net interface pressureto a worst case of 0.38 (a 62-percent life reduction). For a given interference fit, the reduction in life is different for angular-contact and deep-groove ball bearings. Interference fits also affect the maximum Hertz stress-life relation. Experimental data of Czyzewski, showing the effect of interference fit on rolling-element fatigue life, were reanalyzed to determine the shear stress-life exponent. The Czyzewski data shear stress-life exponent c equals 8.77, compared with the assumed value of 9. Results are presented as tables and charts of life factors for angular-contact and deep-groove ball bearings with light, normal, and heavy loads and interference fits ranging from extremely light to extremely heavy.