ISO/TC 4/SC 8 - Load ratings and life

This document specifies supplementary background information regarding the derivation of formulae and factors given in ISO 76:2006.

This document specifies supplementary background information regarding the derivation of mathematical expressions and factors given in ISO 281:2007.

This document gives supplementary background information regarding the derivation of factors given in ISO 20015.

ISO 15312:2018 defines the thermal speed rating for oil bath lubricated rolling bearings and defines calculation principles for the determination of this parameter. The parameter determined in accordance with this document applies to rolling bearings of the given series and sizes of standard design or of a design that, from a frictional point of view, can be related to a standard design bearing. In most cases of standard assembly, the permissible temperature determines the maximum operating speed. Heating of the assembly is then generated by the bearing. Thrust ball bearings are excluded from this document as kinematic effects do not allow the thermal speed rating defined in this document to be applied. NOTE 1 In Annex A mean values for the coefficients f0r and f1r are given ? f0r for calculating viscous losses of oil bath lubricated bearings and f1r for calculating frictional losses of bearings. NOTE 2 Explanatory notes on the limiting criterion are given in Annex B. NOTE 3 In Annex C the reference conditions for grease lubrication are defined. The reference conditions are chosen such that the thermal speed rating for grease lubrication is identical to that for oil bath lubrication.

ISO 20056-2:2017 specifies methods of calculating the static load ratings for hybrid bearings with bearing rings made of contemporary, commonly used, high quality hardened bearing steel, in accordance with good manufacturing practice, and a full set of rolling elements made of silicon nitride (Si3N4) in contemporary, commonly used material and manufacturing quality. For balls, ISO 26602,[4] together with ISO 3290‑2,[1] is applicable. For rollers, ISO 12297‑2[2] is applicable, and ISO 26602[4] is applicable in an analogous way. For applications where hybrid bearings are used, guideline values of the static safety factor, S0, according to Table 1 and Table 2 are observed.

ISO 20056-1:2017 specifies methods of calculating the dynamic load ratings 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 from silicon nitride in contemporary, commonly used, high material and manufacturing quality and surface finish. For balls, ISO 26602[6] together with ISO 3290‑2[2] are applicable. For rollers, ISO 12297‑2[3] is applicable and ISO 26602[6] is applicable in an analogous way.

ISO 20015:2017 specifies methods of calculating the static load rating and the dynamic load rating for spherical plain bearings within the size ranges shown in ISO 12240-1, ISO 12240-2 and ISO 12240-3. Rod ends according to ISO 12240-4 are excluded.

ISO 14728-2:2017 specifies methods of calculating the basic static load rating, static equivalent load and static safety factor for linear motion rolling bearings manufactured from contemporary, commonly used, high quality, hardened bearing steel in accordance with good manufacturing practice and basically of conventional design with regard to the shape of the rolling contact surfaces. ISO 14728-2:2017 is not applicable to designs where the rolling elements operate directly on the slide surface of the machine equipment, unless that surface is equivalent in all respects to the raceway of the linear motion rolling bearing component it replaces.

ISO 14728-1:2017 specifies methods of calculating the basic dynamic load rating and basic rating life for linear motion rolling bearings manufactured from contemporary, commonly used, high quality, hardened bearing steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of the rolling contact surfaces. The life of linear motion rolling bearings is defined and the conditions are established for reliable life calculations. ISO 14728-1:2017 is not applicable to designs where the rolling elements operate directly on the slide surface of the machine equipment, unless that surface is equivalent in all respects to the raceway of the linear motion rolling bearing component it replaces.

This Technical Specification contains recommendations for the calculation of the modified reference rating life taking into consideration lubrication, contamination and fatigue load limit of the bearing material, as well as tilting or misalignment, operating clearance of the bearing and internal load distribution on rolling elements. The calculation method provided in this Technical Specification covers influencing parameters additional to those described in ISO 281. The directions and limitations given in ISO 281 apply to this Technical Specification. The calculation methods pertain to the fatigue life of the bearings. Other mechanisms of failure, like wear or microspalling (gray staining), lie outside the scope of this Technical Specification. This Technical Specification applies to tilted single-row radial ball bearings, subjected to radial and axial load and with radial clearance and tilt taken into account. It also applies to tilted single-row roller bearings, subjected to pure radial load and with radial clearance, edge stress and tilt taken into account. References to methods for the analysis of the internal load distribution under general load are given. The analysis of internal load distribution and modified reference rating life for multi-row bearings or bearings of a more complex geometry can be derived from the equations given in this Technical Specification. For these bearings, the load distribution for each individual row has to be considered. This Technical Specification is primarily intended to be used for computer programs and together with ISO 281 covers the information needed for life calculations. For accurate life calculations under the operating conditions specified above, it is recommended that either this Technical Specification or advanced computer calculations provided by bearing manufacturers, for determining the dynamic equivalent reference load under different loading conditions, be used.

ISO 281:2007 introduced a life modification factor, aISO, based on a systems approach to life calculation, in addition to the life modification factor, a1.These factors are applied in the modified rating life equation, Lnm = a1aISOL10. The modification factor for reliability, a1, for a range of reliability values, is given in ISO 281:2007 as well as the method for evaluating the modification factor for systems approach, aISO. L10 is the basic rating life. ISO/TR 1281-2:2008 gives supplementary background information regarding the derivation of a1 and aISO.

ISO/TS 16281:2008 contains recommendations for the calculation of the modified reference rating life taking into consideration lubrication, contamination and fatigue load limit of the bearing material, as well as tilting or misalignment, operating clearance of the bearing and internal load distribution on rolling elements. The calculation method provided in ISO/TS 16281:2008 covers influencing parameters additional to those described in ISO 281. The directions and limitations given in ISO 281 apply to ISO/TS 16281:2008. The calculation methods pertain to the fatigue life of the bearings. Other mechanisms of failure, like wear or microspalling (gray staining), lie outside the scope of ISO/TS 16281:2008. ISO/TS 16281:2008 applies to tilted single-row radial ball bearings, subjected to radial and axial load, and with radial clearance and tilt taken into account. It also applies to tilted single-row roller bearings, subjected to pure radial load and with radial clearance, edge stress and tilt taken into account. References to methods for the analysis of the internal load distribution under general load are given. The analysis of internal load distribution and modified reference rating life for multi-row bearings or bearings of a more complex geometry can be derived from the equations given in ISO/TS 16281:2008. For these bearings, the load distribution for each individual row has to be considered. ISO/TS 16281:2008 is primarily intended to be used for computer programs and together with ISO 281 covers the information needed for life calculations. For accurate life calculations under the operating conditions specified above, it is recommended that either ISO/TS 16281:2008 or advanced computer calculations provided by bearing manufacturers, for determining the dynamic equivalent reference load under different loading conditions, be used.

ISO 281:2007 specifies methods of calculating the basic dynamic load rating of rolling bearings within the size ranges shown in the relevant ISO publications, manufactured from contemporary, commonly used, high quality hardened bearing steel, in accordance with good manufacturing practice and basically of conventional design as regards the shape of rolling contact surfaces. ISO 281:2007 also specifies methods of calculating the basic rating life, which is the life associated with 90 % reliability, with commonly used high quality material, good manufacturing quality and with conventional operating conditions. In addition, it specifies methods of calculating the modified rating life, in which various reliabilities, lubrication condition, contaminated lubricant and fatigue load of the bearing are taken into account. ISO 281:2007 does not cover the influence of wear, corrosion and electrical erosion on bearing life. ISO 281:2007 is not applicable to designs where the rolling elements operate directly on a shaft or housing surface, unless that surface is equivalent in all respects to the bearing ring (or washer) raceway it replaces.

ISO 76:2006 specifies methods of calculating the basic static load rating and the static equivalent load for rolling bearings within the size ranges shown in the relevant ISO standards, manufactured from contemporary, commonly used, high quality, hardened bearing steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of the rolling contact surfaces. Calculations carried out in accordance with ISO 76:2006 do not yield satisfactory results for bearings in which, because of application conditions and/or internal design, there is a considerable truncation of the area of contact between the rolling elements and the ring raceways. The same limitation applies where application conditions cause deviations from a normal load distribution in the bearing, for example misalignment, preload or extra large clearance or where special surface treatment or coatings are used. Where there is reason to assume that such conditions prevail, the user should consult the bearing manufacturer for recommendations and the evaluation of the static equivalent load. ISO 76:2006 is not applicable to designs where the rolling elements operate directly on a shaft or housing surface, unless that surface is equivalent in all respects to the bearing surface it replaces. Double-row radial bearings and double-direction thrust bearings are, when referred to in ISO 76:2006, presumed to be symmetrical. In addition, guidelines are given for static safety factors to be applied in heavy loaded applications.

ISO/TR 1281-1:2008 gives supplementary background information regarding the derivation of mathematical expressions and factors given in ISO 281:2007.

ISO 14728-2:2004 specifies methods of calculating the basic static load rating, static equivalent load and static safety factor for linear motion rolling bearings manufactured from contemporary, commonly used, high quality, hardened bearing steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of the rolling contact surfaces. ISO 14728-2:2004 is not applicable to designs where the rolling elements operate directly on the slide surface of the machine equipment, unless that surface is equivalent in all respects to the raceway of the linear motion rolling bearing component it replaces.

ISO 14728-1:2004 specifies methods of calculating the basic dynamic load rating and basic rating life for linear motion rolling bearings manufactured from contemporary, commonly used, high quality, hardened bearing steel in accordance with good manufacturing practice and basically of conventional design as regards the shape of the rolling contact surfaces. The life of linear motion rolling bearings is defined and the conditions are established for reliable life calculations. ISO 14728-1:2004 is not applicable to designs where the rolling elements operate directly on the slide surface of the machine equipment, unless that surface is equivalent in all respects to the raceway of the linear motion rolling bearing component it replaces.

ISO 15312:2003 defines the thermal speed rating for oil bath lubricated rolling bearings and defines calculation principles for the determination of this parameter. The parameter determined in accordance with this International Standard applies to rolling bearings of the given series and sizes of standard design or of a design that, from a frictional point of view, can be related to a standard design bearing. Thrust ball bearings are excluded from ISO 15312:2003 as kinematic effects do not allow the thermal speed rating defined in this International Standard to be applied.

Specifies methods of calculating the basic dynamic load rating of rolling bearings, manufactured from hardened steel, as well as the basic rating life and the adjusted rating life. Does not apply to designs where the rolling elements operate directly on a shaft or housing surface.

This second edition cancels and replaces the first edition (ISO 76 : 1978), of which it constitutes a technical revision. Specifies methods of calculating. Does not apply to designs where the rolling elements operate directly on a shaft or housing surface.

Gives supplementary background information regarding the derivation of formulae and factors given in ISO 282/1.