Effect of Roller Geometry on Roller Bearing Load-Life Relation

Cylindrical roller bearings typically employ roller profile modification to equalize load distribution, minimize stress concentration at roller ends and allow for a small amount of misalignment. The 1947 Lundberg-Palmgren analysis reported an inverse fourth power relation between load and life for roller bearings with line contact. In 1952, Lundberg and Palmgren changed their load-life exponent to 10/3 for roller bearings, assuming mixed line and point contact. The effect of roller-crown profile was reanalyzed in this paper to determine the actual load-life relation for modified roller profiles. For uncrowned rollers (line contact), the load-life exponent is p = 4, in agreement with the 1947 Lundberg-Palmgren value but crowning reduces the value of the exponent, p. The lives of modern roller bearings made from vacuum-processed steels significantly exceed those predicted by the Lundberg-Palmgren theory. The Zaretsky rolling-element bearing life model of 1996 produces a load-life exponent of p = 5 for flat rollers, which is more consistent with test data. For the Zaretsky model with fully crowned rollers p = 4.3. For an aerospace profile and chamfered rollers, p = 4.6. Using the 1952 Lundberg-Palmgren value p = 10/3, the value incorporated in ANSI/ABMA and ISO bearing standards, can create significant life calculation errors for roller bearings.