1、Designation: F2488 05 (Reapproved 2013)Standard Terminology forRolling Element Bearings1This standard is issued under the fixed designation F2488; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This terminology covers terms and their definitionsrelevant to the materials and processes associated with rollingelement bearings.2. Terminol
3、ogy2.1 Definitions:absolute viscosity (), n(sometimes called dynamic viscos-ity or just viscosity )a measure of the tendency of the fluidto resist shear.acid number, nmeasure of the quality of a lubricant. Highacid numbers (much higher than the fresh oil) are anindication of lubricant oxidation/degr
4、adation.DISCUSSIONOils with high acid numbers should not be used. Acidnumber is measured as milligrams of KOH needed to neutralize1gofoil.additive, nany chemical compound added to a lubricant toimprove or meet special needs necessary for service (formu-lated lubricants). The most important additives
5、 areantioxidants, rust, and corrosion inhibitors, and extremepressure (EP) and antiwear (AW) additives.antioxidants (oxidation inhibitors), n chemical compoundsused to improve the oxidation stability and subsequentdeterioration of lubricants.average life (L50), nfor a radial roller bearing, the numb
6、er ofrevolutions that 50 % of a group of bearings will complete orexceed before the first evidence of fatigue develops.DISCUSSIONThe average life maybe as much as five times the ratinglife.ball gage (S), n prescribed small amount by which the lotmean diameter should differ from nominal diameter, thi
7、samount being one of an established series of amounts.DISCUSSIONA ball gage, in combination with the ball grade andnominal ball diameter, should be considered as the most exact ball sizespecification to be used by a customer for ordering purposes.ball gage deviation (S), ndifference between the lot
8、meandiameter and the sum of the nominal diameter and the ballgage.ball grade (G), nspecific combination of dimensional formand surface roughness tolerances. A ball grade is designatedby a grade number followed by the letter “C” indicatingsilicon nitride ceramic.boundary lubrication, ncondition of lu
9、brication in whichthe friction between two surfaces in relative motion isdetermined by the roughness of the surfaces and by theproperties of the lubricant other than viscosity.DISCUSSIONAntiwear and extreme pressure additives reduce thewear of components operating under this regime.case depth, nthic
10、kness, measured radially from the surfaceof the hardened case to a point at which carbon content orhardness becomes the same as the ball core.centipoise, nunit of dynamic viscosity.DISCUSSIONThe unit in the cgs system is 1 centipoise (cP). The SIunit of dynamic viscosity is 1 Pa-s and equivalent to
11、103cP.centistoke, nunit of kinematic viscosity.DISCUSSIONThe unit in the cgs system is 1 centistoke (cSt). The SIunit of kinematic viscosity is 1 m2/s and is equivalent to 106cSpatibility, nmeasure of the ability of a lubricant to bemixed with other lubricants or bearing preservatives (fluidsthat fo
12、rm films on metal surfaces to prevent corrosion duringstorage) to form a uniform mixture without causing anyresultant reaction or precipitation of material. Compatibilityis also a measure of the ability of a lubricant not to cause anydetrimental effect to metal, plastic, or elastomer materials.DISCU
13、SSIONIt is recommended that any preservative material beremoved from bearings before lubrication.contamination, n(1) presence of mostly solid foreign mate-rials like sand, grinding powder, dust, and so forth, in alubricant that might cause an increase in wear, torque, andnoise and result in reduced
14、bearing life; and (2) presence offluids like water, solvents, and other oils that might causeaccelerated oxidation, washout, rusting, or crystallization ofthe additives and other phenomena that reduce a bearingslife.corrosion, ngradual destruction of a metal surface as a resultof chemical attack cau
15、sed by polar or acidic agents like1This terminology is under the jurisdiction of ASTM Committee F34 on RollingElement Bearings and is the direct responsibility of Subcommittee F34.91 onEditorial and Terminology.Current edition approved May 1, 2013. Published May 2013. Originallyapproved in 2005. Las
16、t previous edition approved in 2005 as F2488 05. DOI:10.1520/F2488-05R13.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1humidity (water), compounds formed by lubricantdeterioration, or contaminants from the environment.corrosion inhi
17、bitors, ncorrosion inhibitors protect metalsurfaces against corrosion or rust by forming a protectivecoating or by deactivation of corrosive compounds formedduring the operation of a bearing.density, nmass per unit volume of a substance.DISCUSSIONThe cgs unit of density () is 1 g/cm3, and the SI uni
18、tof density is 1 kg/m3. Density depends on the chemical compositionand in itself is no criterion of quality. It is a weak function oftemperature and pressure for liquids and solids.deviation from spherical form (Rw),ngreatest radialdistance in any radial plane between a sphere circumscribedaround th
19、e ball surface and any point on the ball surface.DN value, n product of the bearing bore diameter inmillimetres multiplied by the speed in revolutions perminute (compare to nDmvalue).dynamic viscosity, nanother name for absolute viscosity.EP lubricants (extreme pressure lubricants), nlubricants(oil
20、or greases) that contain extreme pressure additives toprotect the bearings against wear and welding (scoring).esters, nesters are formed from the reaction of acids andalcohols. Esters form a class of synthetic lubricants.DISCUSSIONEsters of higher alcohols with divalent fatty acids formdiester lubri
21、cants while esters of polyhydric alcohols are called thepolyol ester lubricants. These latter esters have higher viscosity and aremore heat resistant than diesters.evaporation loss, nlubrication fluid losses occurring athigher temperatures or under vacuum, or both, as a result ofevaporation.DISCUSSI
22、ONThis can lead to an increase in lubricant consumptionand also to an alteration of the fluid properties of a lubricant (especiallyan increase in the viscosity of blended lubricants). The evaporation lossis expressed as a weight loss in milligrams (10-6kg) or wt %.fire point, nlowest temperature at
23、which the vapor or alubrication fluid ignites under specified test conditions andcontinues to burn for at least 5 s without the benefit of anoutside flame. The fire point is a temperature above the flashpoint.DISCUSSIONPerfluoropolyethers have no fire point.flash point, nlowest temperature of a lubr
24、ication fluid atwhich the fluid gives off vapors that will ignite when a smallflame is periodically passed over the liquid surface underspecified test conditions.DISCUSSIONThe flash and fire points provide a rough characteriza-tion of the flammable nature of lubrication fluids. Perfluoropolyethersha
25、ve no flash point.fretting corrosion, nspecial type of wear produced onmaterials in intimate contact that are subjected to thecombined action of oscillatory motions of small amplitudesand high frequencies. Fretting corrosion appears similar toatmospheric corrosion (rust) as a reddish-brown layer ons
26、teel surfaces.interfacial tension, nwhen two immiscible liquids are incontact, their interface has many characteristics in commonwith a gas-liquid surface. This interface possesses interfacialfree energy because of the unbalanced attractive forcesexerted on the molecules at the interface by the mole
27、culeswithin the separate phases. This free energy is called theinterfacial tension.kinematic viscosity, nratio of absolute viscosity to fluiddensity.DISCUSSIONThis ratio arises frequently in lubrication analyses, andthus, kinematic viscosity has become a separate term describing theviscosity of a fl
28、uid. Many experimental measurements of viscosity offluids result in a measure of kinematic viscosity from which absoluteviscosity is calculated. See absolute viscosity. The cgs unit ofkinematic viscosity is cSt and the SI unit is m2/s. The viscosity of aPREB oil is a major factor in lubricant select
29、ion. The viscosity isdirectly involved in frictional, thermal, and fluid film conditions thatreflect the influence of load, speed, temperature, and design character-istics of the bearing being lubricated.marking increments, nstandard unit steps to express thespecific diameter.mineral oil, noils base
30、d on petroleum stocks. These oilscome in two types, naphthenic and paraffinic. The naph-thenic oils contain unsaturated hydrocarbons, usually in theform of aromatic species. The paraffinic oils are primarilysaturated hydrocarbons with only low levels of unsaturation.nDmvalue (index), nalso called sp
31、eed indexrelativeindicator of the lubricant stress imposed by a bearingrotating at a given speed, where n is the rotational speed ofthe rolling element bearing in revolutions per minute and Dmis the mean diameter in millimetres (arithmetic mean of borediameter d and outside diameter D).DISCUSSIONThe
32、 speed index is multiplied by a factor kadependingon the roller element bearing type:ka= 1 for deep groove ball bearings, angular contact ball bearings,self-aligning ball bearings, radially loaded cylindrical roller bearings,and thrust ball bearings;ka= 2 for spherical roller bearings, taper roller
33、bearings, and needleroller bearings; andka= 3 for axially loaded cylindrical roller bearings and fullcomplement roller bearings.The factor katakes into account the various rates of sliding frictionthat usually occurs during the operation of a rolling element bearing.The nDmvalue is an aid in choosin
34、g a suitable lubricant viscosity fora given bearing speed and is particularly applicable to grease-lubricatedbearings.neutralization number, nmeasure of the acidity or alkalinityof a lubricating fluid. The test determines the quantity ofbase (milligrams of potassium hydroxide) or acid (alsoexpressed
35、 as milligrams of potassium hydroxide) needed toneutralize the acidic or alkaline compounds present in alubricating fluid.DISCUSSIONActually, the neutralization number is not one numberbut several numbers: strong acid number, total acid number, strong basenumber, and total base number. The neutraliz
36、ation number is used forquality control and to determine changes that occur in a lubricant inservice.oxidation stability, nstability of a lubricant in the presenceof air or oxygen is an important chemical property.F2488 05 (2013)2DISCUSSIONOxidation stability has a strong influence on numerousphysic
37、al properties of a lubricant. These properties include the changeof viscosity under static conditions for long periods of time (storage) orwhen exposed to temperatures high above room temperature, or both.The slow chemical reaction of fluid (base oil) and oxygen (air) is calledoxidation. Inhibitors
38、(see antioxidants) are used to improve theoxidation stability of the lubricants. Synthetic fluids, especially per-fluoropolyethers and silicones, are much more resistant to oxidationthan mineral oils.part number, npart number is developed by selecting acharacteristic from each of the tables in a spe
39、cification sheet,for example:M81793/XX-XXXXXXXXXpassivation, ntreatment for corrosion-resistant steel to elimi-nate corrodible surface impurities and provide a protectivefilm.perfluoropolyethers (PFPE or PFAE), n fully fluorinatedlong-chain aliphatic ethers.DISCUSSIONThe perfluoropolyethers show som
40、e extraordinaryproperties like chemical inertness, nonflammability, high thermal andoxidative resistance, very good viscosity-temperature characteristics,and compatibility with a wide range of materials, including metals andplastics. The perfluoropolyethers, however, are not suitable for use withalu
41、minum, magnesium, and titanium alloys. The perfluoropolyethersare not compatible with other types of synthetic fluids and mineral oilsand cannot dissolve common lubricant additives.pH value, nscale for measuring the acidity or alkalinity of aproduct. Zero pH is very acid, 7 is neutral, and 14 is ver
42、yalkaline.poise (P), n see centipoise (cP).pour point, nof a lubricating fluid , the lowest temperatureat which the lubricating fluid will pour, or flow.pressure-viscosity coefficient, ndynamic viscosity of a fluidincreases with increasing pressure.DISCUSSIONThe dependence of viscosity (absolute), ,
43、 on pressure,p, can be expressed by the equation: 5 0expp! (1)where: = absolute viscosity at pressure, p,0= absolute viscosity at one atmosphere, and = the pressure-viscosity coefficient.The pressure-viscosity coefficient is very small and varies with thechemical composition of the fluid.One limitat
44、ion of the use of 0and the corresponding equation is thatthe measurements of 0are made under static conditions where thepressure is held constant while the viscosity attains a steady-state value.In actual bearing operations, the lubricant may see high pressure in thecontact zone for only a few milli
45、seconds and the viscosity changes asa result of this high pressure may not reach steady-state values.rated viscosity, (1), n kinematic viscosity attributed to adefined lubricating condition of a rolling element bearing.The rated viscosity is a function of the speed and can bedetermined by the mean b
46、earing diameter in millimetres(10-3m) and the rotational speed (rpm).rating life (L10), nfor a radial roller bearing, the number ofrevolutions that 90 % of a group of bearings will complete orexceed before the first evidence of fatigue developsrepeatability, ncriterion for judging the acceptability
47、of testresults. Repeatability is the difference between successivetest results obtained by the same operator with the sameapparatus under constant operating conditions on identicaltest material.DISCUSSIONRepeatability is usually reported as a range of valuesthat would, in the normal and correct oper
48、ation of the test method,encompass two standard deviations from the median value of the test.reproducibility, ncriterion for judging the acceptability oftest results. Reproducibility is the difference between twosingle and independent results obtained by different opera-tors working with identical t
49、est material.DISCUSSIONThis difference, in the long run and under normal andcorrect operation of the test method, would not exceed a specifiedvalue.saponification number, nmeasure of the amount of constitu-ents of a lubrication fluid that will easily saponify under testconditions. The saponification number is expressed in mil-ligrams of potassium hydroxide that are required to neutral-ize the free and bonded acids contained in1goflubricatingfluid. The saponification number is a measure of fatty aci
