The Design of Rolling Bearing Mountings

GlossaryL h = 500 · f Lp[h]p = 3 for ball bearingsp = 10 for roller bearings and needle roller bearings3Index of static stressing f sThe index of static stressing f s for statically loaded bearingsis calculated to ensure that a bearing with an adequateload carrying capacity has been selected. It is calculatedfrom the static load rating C 0 and the equivalentstatic load P 0 .f s = C 0P 0The index f s is a safety factor against permanent deformationsof the contact areas between raceway and themost heavily loaded rolling element. A high f s value isrequired for bearings which must run smoothly andparticularly quietly. Smaller values suffice where amoderate degree of running quietness is required. Thefollowing values are generally recommended:f s = 1.5...2.5 for a high degreef s = 1...1.5 for a normal degreef s = 0.7...1 for a moderate degreeValue K 1a ball bearingsb tapered roller bearings, cylindrical roller bearingsc spherical roller bearings, spherical roller thrust bearings 3) , cylindrical roller thrust1), 3)bearings1), 2)d full complement cylindrical roller bearings4d3c2K 1 b1a00 2 4 6 8 10 12f s*1)Attainable only with lubricant filtering corresponding to V < 1, otherwiseK 1 ≥ 6 must be assumed.2)To be observed for the determination of : the friction is at least twice the valuein caged bearings. This results in higher bearing temperature.3)Minimum load must be observed.Value K 27654K 3 221κ=4κ=2κ=0.4**κ=0.700 2 4 6 8 10 12f s*K 2 equals for 0 for lubricants with additives with a corresponding suitability proof.** With 0.4 wear dominates unless eliminated by suitable additives.κ=1κ=0.35**κ=0.3**κ=0.25**κ=0.2**K valueThe K value is an auxiliary quantity needed to determinethe basic a 23II factor when calculating the attainablelife of a bearing.K = K 1 + K 2K 1 depends on the bearing type and the stress index f s* ,see diagram.K 2 depends on the stress index f s* and the viscosity ratio. The values in the diagram (below) apply to lubricantswithout additives and lubricants with additiveswhose effects in rolling bearings was not tested.With K = 0 to 6, the basic a 23II value is found on one ofthe curves in zone II of diagram 3 on page 185 (cp.factor a 23 ).Kinematically permissible speedThe kinematically permissible speed is indicated in theFAG catalogues also for bearings for which – accordingto DIN 732 – no thermal reference speed is defined.Decisive criteria for the kinematically permissiblespeed are e.g. the strength limit of the bearing componentsor the permissible sliding velocity of rubbingseals. The kinematically permissible speed can bereached, for example, with– specially designed lubrication– bearing clearance adapted to the operatingconditions– accurate machining of the bearing seats– special regard to heat dissipationLifeCp. also Bearing life.187 FAG