1、Designation: F 2488 05Standard Terminology forRolling Element Bearings1This standard is issued under the fixed designation F 2488; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses i
2、ndicates the year of last reapproval. Asuperscript epsilon (e) 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. Terminology2.1 Definiti
3、ons:absolute viscosity (h), 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/degradation.DISCUSS
4、IONOils 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 are antioxi-da
5、nts, rust, and corrosion inhibitors, and extreme pressure(EP) and antiwear (AW) additives.antioxidants (oxidation inhibitors), nchemical compoundsused to improve the oxidation stability and subsequentdeterioration of lubricants.average life (L50), nfor a radial roller bearing, the number ofrevolutio
6、ns 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), nprescribed small amount by which the lotmean diameter should differ from nominal diameter, thisamount being o
7、ne 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 (DS), ndifference between the lot meandiameter a
8、nd 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 lubrication in w
9、hichthe 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, nthickness, measure
10、d 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 103cP.centisto
11、ke, 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 form films on me
12、tal 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.DISCUSSIONIt is rec
13、ommended that any preservative material beremoved from bearings before lubrication.contamination, n(1) presence of mostly solid foreign ma-terials like sand, grinding powder, dust, and so forth, in alubricant that might cause an increase in wear, torque, andnoise and result in reduced bearing life;
14、and (2) presence offluids like water, solvents, and other oils that might cause1This 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 July 1, 2005. Publi
15、shed August 2005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.accelerated oxidation, washout, rusting, or crystallization ofthe additives and other phenomena that reduce a bearingslife.corrosion, ngradual destruction of a metal su
16、rface as a resultof chemical attack caused by polar or acidic agents likehumidity (water), compounds formed by lubricant deterio-ration, or contaminants from the environment.corrosion inhibitors, ncorrosion inhibitors protect metalsurfaces against corrosion or rust by forming a protectivecoating or
17、by deactivation of corrosive compounds formedduring the operation of a bearing.density, nmass per unit volume of a substance.DISCUSSIONThe cgs unit of density (r) is 1 g/cm3, and the SI unitof density is 1 kg/m3. Density depends on the chemical compositionand in itself is no criterion of quality. It
18、 is a weak function oftemperature and pressure for liquids and solids.deviation from spherical form (DRw), ngreatest radialdistance in any radial plane between a sphere circumscribedaround the ball surface and any point on the ball surface.DN value, nproduct of the bearing bore diameter in milli-met
19、res multiplied by the speed in revolutions per minute(compare to nDmvalue).dynamic viscosity, nanother name for absolute viscosity.EP lubricants (extreme pressure lubricants), nlubricants(oil or greases) that contain extreme pressure additives toprotect the bearings against wear and welding (scoring
20、).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 lubricants while esters of polyhydric alcohols are called thepolyol ester lubricants. These latter esters have hi
21、gher viscosity and aremore heat resistant than diesters.evaporation loss, nlubrication fluid losses occurring athigher temperatures or under vacuum, or both, as a result ofevaporation.DISCUSSIONThis can lead to an increase in lubricant consumptionand also to an alteration of the fluid properties of
22、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 which the vapor or alubrication fluid ignites under specified test conditions andcontinues to burn for at le
23、ast 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 lubrication fluid atwhich the fluid gives off vapors that will ignite when a smallflame is periodically passed o
24、ver the liquid surface underspecified test conditions.DISCUSSIONThe flash and fire points provide a rough characteriza-tion of the flammable nature of lubrication fluids. Perfluoropolyethershave no flash point.fretting corrosion, nspecial type of wear produced onmaterials in intimate contact that ar
25、e subjected to thecombined action of oscillatory motions of small amplitudesand high frequencies. Fretting corrosion appears similar toatmospheric corrosion (rust) as a reddish-brown layer onsteel surfaces.interfacial tension, nwhen two immiscible liquids are incontact, their interface has many char
26、acteristics 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 moleculeswithin the separate phases. This free energy is called theinterfacial tension.kinematic viscosity, nrat
27、io of absolute viscosity to fluiddensity.DISCUSSIONThis ratio arises frequently in lubrication analyses, andthus, kinematic viscosity has become a separate term describing theviscosity of a fluid. Many experimental measurements of viscosity offluids result in a measure of kinematic viscosity from wh
28、ich 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 selection. The viscosity isdirectly involved in frictional, thermal, and fluid film conditions thatreflect the inf
29、luence 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 based on petroleum stocks. These oilscome in two types, naphthenic and paraffinic. The naph-thenic oils contain
30、unsaturated hydrocarbons, usually in theform of aromatic species. The paraffinic oils are primarilysaturated hydrocarbons with only low levels of unsaturation.nDmvalue (index), nalso called speed indexrelativeindicator of the lubricant stress imposed by a bearingrotating at a given speed, where n is
31、 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 speed index is multiplied by a factor kadependingon the roller element bearing type:ka= 1 for deep groove b
32、all 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 bearings, and needleroller bearings; andka= 3 for axially loaded cylindrical roller bearings and fullcomplem
33、ent 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 choosing a suitable lubricant viscosity fora given bearing speed and is particularly applicable to grease-lubricate
34、dbearings.neutralization number, nmeasure of the acidity or alkalin-ity of a lubricating fluid. The test determines the quantity ofbase (milligrams of potassium hydroxide) or acid (alsoexpressed as milligrams of potassium hydroxide) needed toneutralize the acidic or alkaline compounds present in alu
35、bricating fluid.F2488052DISCUSSIONActually, the neutralization number is not one numberbut several numbers: strong acid number, total acid number, strong basenumber, and total base number. The neutralization number is used forquality control and to determine changes that occur in a lubricant inservi
36、ce.oxidation stability, nstability of a lubricant in the presenceof air or oxygen is an important chemical property.DISCUSSIONOxidation stability has a strong influence on numerousphysical properties of a lubricant. These properties include the changeof viscosity under static conditions for long per
37、iods 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 (see antioxidants) are used to improve theoxidation stability of the lubricants. Synthetic fluids, especially per-
38、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 specification sheet,for example:M81793/XX-XXXXXXXXXpassivation, ntreatment for corrosion-resistant steel toeliminate
39、corrodible surface impurities and provide a pro-tective film.perfluoropolyethers (PFPE or PFAE), nfully fluorinatedlong-chain aliphatic ethers.DISCUSSIONThe perfluoropolyethers show some extraordinaryproperties like chemical inertness, nonflammability, high thermal andoxidative resistance, very good
40、 viscosity-temperature characteristics,and compatibility with a wide range of materials, including metals andplastics. The perfluoropolyethers, however, are not suitable for use withaluminum, magnesium, and titanium alloys. The perfluoropolyethersare not compatible with other types of synthetic flui
41、ds 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 veryalkaline.poise (P), nsee centipoise (cP).pour point, nof a lubricating fluid, the lowest temperature atwhich the l
42、ubricating fluid will pour, or flow.pressure-viscosity coefficient, ndynamic viscosity of a fluidincreases with increasing pressure.DISCUSSIONThe dependence of viscosity (absolute), h, on pressure,p, can be expressed by the equation:h5h0expap! (1)where:h = absolute viscosity at pressure, p,h0= absol
43、ute viscosity at one atmosphere, anda = the pressure-viscosity coefficient.The pressure-viscosity coefficient is very small and varies with thechemical composition of the fluid.One limitation of the use of h0and the corresponding equation is thatthe measurements of h0are made under static conditions
44、 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 milliseconds and the viscosity changes asa result of this high pressure may not reach steady-state values.rated vis
45、cosity, (n1), nkinematic 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 bearing diameter in millimetres(10-3m) and the rotational speed (rpm).rating life (L10), nfor a radial roller b
46、earing, 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 of testresults. Repeatability is the difference between successivetest results obtained by the same operator w
47、ith the sameapparatus under constant operating conditions on identicaltest material.DISCUSSIONRepeatability is usually reported as a range of valuesthat would, in the normal and correct operation of the test method,encompass two standard deviations from the median value of the test.reproducibility,
48、ncriterion for judging the acceptability oftest results. Reproducibility is the difference between twosingle and independent results obtained by different opera-tors working with identical test material.DISCUSSIONThis difference, in the long run and under normal andcorrect operation of the test meth
49、od, would not exceed a specifiedvalue.saponification number, nmeasure of the amount of con-stituents of a lubrication fluid that will easily saponify undertest conditions. The saponification number is expressed inmilligrams of potassium hydroxide that are required toneutralize the free and bonded acids contained in1goflubricating fluid. The saponification number is a measure offatty acids compounded in an oil and a measure of the stateof oil deterioration.saponify, vto hydrolyze an ester and to convert the free aci
