1、Designation: D 6821 02 (Reapproved 2007)An American National StandardStandard Test Method forLow Temperature Viscosity of Drive Line Lubricants in aConstant Shear Stress Viscometer1This standard is issued under the fixed designation D 6821; the number immediately following the designation indicates
2、the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the
3、viscos-ity of drive line lubricants (gear oils, automatic transmissionfluids, and so forth) with a constant shear stress viscometer attemperatures from 40 to 10C after a prescribed preheat andcontrolled cooling to the final test temperature.1.2 The applicability of this particular test method to pet
4、ro-leum products other than drive line lubricants has not beendetermined.1.3 This test method uses the millipascal second (mPas) asthe unit of viscosity. One millipascal second is equal to onecentipoise.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with
5、its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2983 Test Method for Low-Temperature Viscosity ofLubricants Measure
6、d by Brookfield ViscometerD 3829 Test Method for Predicting the Borderline PumpingTemperature of Engine OilD 4684 Test Method for Determination of Yield Stress andApparent Viscosity of Engine Oils at Low Temperature3. Terminology3.1 Definitions:3.1.1 apparent viscositythe determined viscosity obtain
7、edby the use of this test method.3.1.2 Newtonian oil or fluidan oil or fluid that at a giventemperature exhibits a constant viscosity at all shear rates orshear stresses.3.1.3 non-Newtonian oil or fluidan oil or fluid that at agiven temperature exhibits a viscosity that varies with chang-ing shear s
8、tress or shear rate.3.1.4 shear ratethe velocity gradient in fluid flow.3.1.4.1 DiscussionFor a Newtonian fluid in a concentriccylinder rotary viscometer in which the shear stress is mea-sured at the inner cylinder surface (such as the apparatusdescribed in 6.1), and ignoring any end effects, the sh
9、ear rate isgiven as follows:Gr52 V Rs2Rs22 Rr2(1)Gr54 p Rs2tRs22 Rr2!(2)where:Gr= shear rate at the surface of the rotor in reciprocalseconds, s-1,V = angular velocity, rad/s,Rs= stator radius, mm,Rr= rotor radius, mm, andt = time for one revolution of the rotor, s.For the specific apparatus being d
10、escribed in 6.1.1,Gr533t(3)3.1.5 shear stressthe motivating force per unit area forfluid flow.3.1.5.1 DiscussionFor the rotary viscometer being de-scribed in 6.1, the rotor surface is the area under shear or theshear area. For this test method, end effects are not considered.Tr5 9.81 M Ro1 Rt! 3 102
11、6(4)Sr5Tr2 p Rr2h3 109(5)where:Tr= torque applied to rotor, Nm,M = applied mass, g,Ro= radius of the shaft, mm,Rr= radius of the string, mm,Sr= shear stress at the rotor surface, Pa, andh = height of the rotor face, mm.For the dimensions given in 6.1.1,1This test method is under the jurisdiction of
12、ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved Nov. 1, 2007. Published January 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 682102e1.2For referenced ASTM standa
13、rds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
14、 19428-2959, United States.Tr5 32 M 3 1026(6)Sr5 4.5 M (7)3.1.6 viscositythe ratio between the applied shear stressand rate of shear, sometimes called the coefficient of dynamicviscosity.3.1.6.1 DiscussionThis value is thus a measure of theresistance to flow of the liquid. The SI unit of viscosity i
15、s thepascal second Pas. The submultiple unit is millipascalseconds (mPas).3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration oilsthose oils that establish the instru-ments reference framework of apparent viscosity versus speed(angular velocity), from which the apparent viscosities
16、of testoils are determined.3.2.1.1 DiscussionCalibration oils, which are essentiallyNewtonian fluids, are available commercially and are de-scribed in 7.1.3.2.2 test oilany oil for which the apparent viscosity is tobe determined by this test method.3.2.3 yield stressthe shear stress required to init
17、iate flow.3.2.3.1 DiscussionFor Newtonian fluids and some non-Newtonian fluids the yield stress is very small.4. Summary of Test Method4.1 A drive line fluid is preheated to 50C for a specifiedtime and then cooled at a programmed rate (see Table X1.1)tothe final test temperature and soaked at the fi
18、nal temperaturefor a defined period of time.At the completion of the soak time,the viscosity is measured by applying a prescribed torque andmeasuring rotational speed to determine the apparent viscosityof the sample.5. Significance and Use5.1 Viscosity of drive line lubricants at low temperature isc
19、ritical for both gear lubrication and the circulation of the fluidin automatic transmissions. For gear oils (GOs), the issue iswhether the fluid characteristics are such that the oil will flowinto the channel dug out by the submerged gears as they beginrotating and re-lubricating them as they contin
20、ue to rotate. Forautomatic transmission fluids, torque, and tractor fluids theissue is whether the fluid will flow into a pump and through thedistribution system rapidly enough for the device to function.5.2 The low temperature performance of drive line lubricantflow characteristics was originally e
21、valuated by the channeltest. In this test, a pan was filled to a specified depth ofapproximately 2.5 cm and then cooled to test temperature. Thetest was performed by scraping a channel through the full depthof the fluid and across the length of the pan after it had soakedat test temperature for a sp
22、ecified time. The time it took thefluid to cover the channel was measured and reported. Thechannel test was replaced by Test Method D 2983 in 1971.5.3 The results of this test procedure correlate with theviscometric measurements obtained in Test Method D 2983.3The correlation obtained is:V 5 0.941 3
23、 VD 2983(8)where:V = the apparent viscosity measured by this testmethod, andVD 2983= the apparent viscosity measured by TestMethod D 2983.5.3.1 The equation was obtained by forcing the fit throughzero. The coefficient of variation (R2) for this correlation is0.9948.6. Apparatus6.1 Mini-Rotary Viscom
24、eter, an apparatus that consists ofone or more viscometric cells in a temperature controlledaluminum block. Each cell, when fitted with the specified rotor,becomes a calibrated rotor-stator set. Rotation of the rotor isachieved by an applied load acting through a string woundaround the rotor shaft.
25、The top bearing plate is fitted withlocking pins for holding the rotors stationary. Time of rotationis measured electronically by a device attached to the timingwheel.NOTE 1The rotors for use with this test method can be distinguishedfrom the rotors used for other mini-rotary viscometer test methods
26、 by thewhite rotor and the white band on the upper half of the shaft. The whiteband provides rotor identification while the rotor is in the cell.6.1.1 The mini-rotary viscometric cell for this procedure hasthe following typical dimensions:Diameter of rotor 15.0 mmLength of rotor 20.0 mmInside diamet
27、er of cell 19.0 mmRadius of shaft 3.18 mmRadius of string 0.10 mm6.2 Weight, for applying mass. Weights are to be in incre-ments of 2.5 g 6 1 %. A minimum of eight weight segmentswill be needed for the measurements defined in this testmethod.6.3 Temperature Control System, that will regulate thesamp
28、les in the cells according to the cooling program describedin Table X1.1 and within the tolerances specified in the table.6.4 Thermometers, for measuring the temperature of theblock. Two are required, one graduated from at least +40 to90C in 1C subdivisions, and one that has at least a two degreegra
29、duated range around the final test temperature in 0.2Csubdivisions. Other thermometric devices of equal or greateraccuracy and resolution may be used.6.5 Time/Temperature Recording Device, such as a chartrecorder or data logger to verify that the correct cooling of thesamples has been accomplished.7
30、. Reagents and Materials7.1 Calibration Oil, a low cloud-point fluid of approxi-mately 60 000 mPas viscosity at 25C for calibration of theviscometric cells.7.2 Oil Solvent, commercial heptanes or similar solvent forthe test fluids that evaporates without leaving a residue.(WarningFlammable.)7.3 Acet
31、oneA technical grade of acetone is suitable pro-vided it does not leave a residue upon evaporation.(WarningFlammable.)3SAE Paper 1999013672, “Viscosity of Drive-Line Lubricants by a SpecialMini-Rotary Viscometer Technique.” Available from Society of Automotive Engi-neers, 400 Commonwealth Dr., Warre
32、ndale, PA 15096-0001.D 6821 02 (2007)28. Sampling8.1 A representative sample of test oil free from suspendedsolid material and water is necessary to obtain valid viscositymeasurements. If the sample in its container is received belowthe dew-point temperature of the room, allow the sample towarm to r
33、oom temperature before opening the container.9. Calibration9.1 Temperature Sensor CalibrationCalibrate the instru-ments temperature sensor by verifying the displayed tempera-ture with the block temperature measured independently in theleft thermometer well. The sensed temperature should beverified u
34、sing a 36 to +5C reference thermometer with arange of approximately 36 to +5C in 0.2C increments, or anindependent electronic temperature measurement instrument ofequivalent precision at a minimum of three temperatures. Makethese temperature measurements at least 5C apart and equallydistributed over
35、 the test temperature range to establish acalibration curve for this combination of temperature sensorand controller.9.2 Viscometer Cell CalibrationThe calibration cell con-stant of each viscometric cell (viscometer constants) is to bedetermined with the viscosity calibration oil.9.2.1 Use steps 10.
36、2-10.2.5 to place the calibration oil in thecell.9.2.2 Program the temperature controller to cool the mini-rotary viscometer block to the desired calibration temperature25C within1horless, then start the program.9.2.3 Allow the samples to soak at the test temperature60.2C for at least 1 h. Verify th
37、e test temperature by placinga calibrated temperature sensing probe in the left thermometerwell.9.2.4 At the end of the soak period, record the temperaturereading (test temperature) and remove cover of the viscometercell. The temperature made by the independent temperaturesensor in the left thermome
38、ter well reading should agree withthe temperature displayed on the computer screen within0.1C.9.2.5 Measure the time for the first three rotor rotations asdescribed in 10.4.9.2.6 Repeat 9.2.5 for each of the remaining cells, taking thecells in order from left to right.9.2.7 Calculate the viscometer
39、constant for each cell (rotor/stator combination) with the following equation:C 5hot(9)where:ho= viscosity of the calibration oil, mPas (cP) at 25C,C = cell constant for a 20 g mass, Pa, andt = time for three complete rotor revolutions, s.10. Procedure10.1 Program the temperature controller to contr
40、ol themini-rotary viscometer block temperature in accordance withTable X1.1. The programmed temperature is the temperature inTable X1.1 plus the appropriate temperature correction factordetermined in 9.1.10.2 Test Sample and Viscometric Cell Preparation:10.2.1 Remove the nine rotors from the viscome
41、tric cellsand ensure that both the cells and the rotors are clean. See 10.6for the cleaning procedure.10.2.2 Place a 10 6 1 mL oil sample in each cell.10.2.3 Install the white rotors in their proper stator andinstall the upper pivots.NOTE 2The rotors used with this test method are physically differe
42、ntthan those used with other mini-rotary viscometer (MRV) test methods.The rotors are white. To further distinguish them they also have a whiteband on upper part of the shaft to identify the rotor type while in theinstrument. DO NOT use the black rotors for this procedure. The blackrotors are used w
43、ith Test Methods D 3829 and D 4684.10.2.4 Place the loop of the 700 mm long string over thecross arm at the top of the rotor shaft and wind all but 200 mmof the length around the shaft. Do not overlap the strings.Orient the rotor such that a (red or black) marked end of thecross arm at the top of th
44、e shaft is pointing directly forward andlock the rotor with the locking pin. Loop the remaining end ofthe string over the top bearing cover.10.2.4.1 The string may be prewound around the shaftbefore installation of the rotor in step 10.2.3.10.2.5 Place the housing cover over the viscometric cells to
45、minimize the formation of frost on the cold metal parts exposedto air. In some climates, it is desirable to flush the cover withdry air to minimize frost formation.10.2.6 Start the programmed temperature profile.10.2.7 At the completion of the temperature profile, thetemperature of the block should
46、be within 0.2C of the desiredtest temperature, when measured by a thermometer or elec-tronic temperature measuring device other than the temperaturecontroller in the same thermometer well used during calibra-tion. If the block temperature is within this range, proceed withthe yield stress and viscos
47、ity measurements within 30 min ofthe completion of the temperature profile. If the temperaturemeasurements do not agree, check accuracy of external tem-perature sensor. Measuring the ice point is one way to check.If correct, then recalibrate the temperature control system inaccordance with 9.1.10.3
48、Measurement of the Yield Stress (Optional):10.3.1 Beginning with the cell farthest to the left of theinstrument, follow the procedure below for each cell in turn.10.3.2 Align the pulley wheel with the shaft of the cell to betested, such that the string hangs past the front of the housing.Make sure t
49、hat the weights clear the edge of the bench duringtesting.10.3.3 Remove the string from the upper bearing supportand carefully place it over the pulley wheel.10.3.4 Carefully attach a 2.5 g mass to the string.10.3.5 Raise the locking pin. If the cross arm moves morethan 3 mm in 15 s, let it rotate until it clears the cross arm andthen lower the locking pin. (Three millimetres is approximatelytwice the diameter of the cross arm.) Let the rotor continue torotate until the cross arm rests against the locking pin. Removethe weight fr
