DIN ISO 281 Beiblatt 5:2011-10

This supplement has been prepared by the Rolling Bearings and Plain Bearings Standards Committee (NAWGL), Working Committee NA 118-01-08 AA "Tragzahlen und Lebensdauer" ("Load ratings and life"). Hybrid bearings are rolling bearings with raceways consisting of commonly used rolling bearing steel and rolling elements consisting of ceramic. Due to the higher modulus of elasticity of the ceramic rolling elements hybrid bearings have a noticeably smaller contact ellipse at the same load than rolling bearings with rolling elements of steel. This will lead theoretically to a reduction of the dynamic load-carrying ability; however the smaller contact ellipse and the material combination ceramic-steel will lead to noticeably lower surface shear stress in the rolling contact, which again will lead to a higher load-carrying ability. In practice hybrid bearings show at least the same life as bearings with steel rolling elements when used in the typical application range of hybrid bearings. Therefore a reduction of the dynamic load rating for hybrid bearings is not necessary. This supplement applies for hybrid bearings with bearing rings made of contemporary, commonly used, high quality hardened bearing steel, in accordance with good manufacturing practice and rolling elements made of ceramic, usually silicon nitride (Si₃N₄) in contemporary, commonly used material and manufacturing quality. It contains no standardized provisions, but describes a method for the calculation of the dynamic load rating of hybrid bearings. When using hybrid bearings the reduced static load ratings according to DIN ISO 76 Supplement 2 and the recommendations for the static safety factor according to DIN ISO 76 in comparison to conventional rolling bearings shall be observed.