Effect of roller profile on cylindrical roller bearing life prediction - Part I: Comparison of bearing life theories

Four rolling-element bearing life theories were chosen for analysis and com pared for a simple roller-race geometry model. The life theories were those of Weibull; Lundberg and Palmgren; loannides and Harris; and Zaretsky. The analysis without a fatigue limit of loannides and Harris is identical to t he Lundberg and Palmgren analysis, and the Weibull analysis is similar to t hat of Zaretsky if the exponents are chosen to be identical. The resultant predicted life at each stress condition not only depends on the life equati on used but also on the Weibull slope assumed. The least variation in predi cted life with Weibull slope comes with the Zaretsky equation. Except for a Weibull slope of 1.11, at which the Weibull equation predicts the highest lives, the highest lives are predicted by the Zaretsky equation. For Weibul l slopes of 1.5 and 2, both the Lundberg-Palmgren and Ioannides-Harris (whe re tau (u) equals 0) equations predict lower lives than the ANSI/ABMA/ISO s tandard. Based upon the Hertz stresses for line contact, the accepted load- life exponent of 10/3 results in a maximum Hertz stress-life exponent equal to 6.6. This value is inconsistent with that experienced in the field. The assumption of a shear stress fatigue limit tau (u), results in Hertz sb es s-life exponents greater than are experimentally verifiable.