1、Designation: D6821 02 (Reapproved 2007)D6821 12Standard Test Method forLow Temperature Viscosity of Drive Line Lubricants in aConstant Shear Stress Viscometer1This standard is issued under the fixed designation D6821; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the measurement of the viscosity of driv
3、e line lubricants (gear oils, automatic transmission fluids,and so forth) with a constant shear stress viscometer at temperatures from 40 to 10C after a prescribed preheat and controlledcooling to the final test temperature. The precision is stated for test temperatures from -40 to -26C.1.2 The appl
4、icability of this particular test method to petroleum products other than drive line lubricants has not beendetermined.1.3 This test method uses the millipascal second (mPas) as the unit of viscosity. One millipascal second is equal to onecentipoise. The values stated in SI units are to be regarded
5、as standard. No other units of measurement are included in this standard.1.3.1 This standard uses the SI based unit of milliPascal second (mPas) for viscosity which is equivalent to centiPoise (cP).1.4 This standard does not purport to address all of the safety concerns, if any, associated with its
6、use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2983 Test Method for Low-Temperature Viscosity of Lubricants Measured by Br
7、ookfield ViscometerD3829 Test Method for Predicting the Borderline Pumping Temperature of Engine OilD4684 Test Method for Determination of Yield Stress and Apparent Viscosity of Engine Oils at Low TemperatureD6896 Test Method for Determination of Yield Stress and Apparent Viscosity of Used Engine Oi
8、ls at Low TemperatureE1137 Specification for Industrial Platinum Resistance Thermometers3. Terminology3.1 Definitions:3.1.1 apparent viscosityviscosity, nthe determined viscosity obtained by the use of this test method.3.1.2 Digital Contact Thermometer (DCT), nan electronic device consisting of a di
9、gital display and associated temperaturesensing probe.3.1.2.1 DiscussionThis device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a dig
10、ital output or display,or both, of the temperature. The temperature sensing probe is in contact with the material whose temperature is being measured.This device is sometimes referred to as a digital thermometer.3.1.3 Newtonian oil or fluidfluid, nan oil or fluid that at a given temperature exhibits
11、 a constant viscosity at all shear ratesor shear stresses.1 This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products and Lubricants and is the direct responsibility of Subcommittee D02.07 onFlow Properties.Current edition approved Nov. 1, 2007Nov. 1, 2012. Published Jan
12、uary 2008April 2013. Originally approved in 2002. Last previous edition approved in 20022007 asD6821D682102(2007).021. DOI: 10.1520/D6821-02R07.10.1520/D6821-12.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of
13、 ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technicall
14、y possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this stand
15、ardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.4 non-Newtonian oil or fluidfluid, nan oil or fluid that at a given temperature exhibits a viscosity that varies withchanging shear stress or shear rate.3.1.5 shear raterate, nthe
16、 velocity gradient in fluid flow.3.1.5.1 DiscussionFor a Newtonian fluid in a concentric cylinder rotary viscometer in which the shear stress is measured at the inner cylinder surface(such as the apparatus described in 6.1), and ignoring any end effects, the shear rate is given as follows:Gr 5 2Rs2R
17、s22Rr2 (1)Gr 5 4piRs2tRs22Rr2! (2)where:Gr = shear rate at the surface of the rotor in reciprocal seconds, s-1, = 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 described in 6.1.1,Gr 533t (3)3.1.6
18、shear stressstress, nthe motivating force per unit area for fluid flow.3.1.6.1 DiscussionFor the rotary viscometer being described in 6.1, the rotor surface is the area under shear or the shear area. For this test method,end effects are not considered.Tr 59.81 M Ro1Rt!31026 (4)Sr 5 Tr2piRr2 h 3109 (
19、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,Tr 532 M 31026 (6)Sr 54.5 M (7)3.1.7 viscosityviscosity, nthe rati
20、o between the applied shear stress and rate of shear, sometimes called the coefficient ofdynamic viscosity.3.1.7.1 DiscussionThis value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the pascal second Pas. Thesubmultiple unit is millipascal seconds (mPas).3.2
21、Definitions of Terms Specific to This Standard:3.2.1 calibration oilsoils, nthose oils that establish the instruments reference framework of apparent viscosity versus speed(angular velocity), from which the apparent viscosities of test oils are determined.3.2.1.1 DiscussionD6821 122Calibration oils,
22、 which are essentially Newtonian fluids, are available commercially and are described in 7.1.3.2.2 test oiloil, nany oil for which the apparent viscosity is to be determined by this test method.3.2.3 yield stressstress, nthe shear stress required to initiate flow.3.2.3.1 DiscussionFor Newtonian flui
23、ds 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 specified time and then cooled at a programmed rate (see Table X1.1) to thefinal test temperature and soaked at the final temperature for a defined period of time
24、. At the completion of the soak time, theviscosity is measured by applying a prescribed torque and measuring rotational speed to determine the apparent viscosity of thesample.5. Significance and Use5.1 Viscosity of drive line lubricants at low temperature is critical for both gear lubrication and th
25、e circulation of the fluid inautomatic transmissions. For gear oils (GOs), the issue is whether the fluid characteristics are such that the oil will flow into thechannel dug out by the submerged gears as they begin rotating and re-lubricating them as they continue to rotate. For automatictransmissio
26、n fluids, torque, and tractor fluids the issue is whether the fluid will flow into a pump and through the distribution systemrapidly enough for the device to function.5.2 The low temperature performance of drive line lubricant flow characteristics was originally evaluated by the channel test.In this
27、 test, a pan was filled to a specified depth of approximately 2.5 cm and then cooled to test temperature. The test wasperformed by scraping a channel through the full depth of the fluid and across the length of the pan after it had soaked at testtemperature for a specified time. The time it took the
28、 fluid to cover the channel was measured and reported. The channel test wasreplaced by Test Method D2983 in 1971.5.3 The results of this test procedure correlate with the viscometric measurements obtained in Test Method D2983.3 Thecorrelation obtained is:V 50.9413VD2983 (8)where:V = the apparent vis
29、cosity measured by this test method, andVD2983 = the apparent viscosity measured by Test Method D2983.5.3.1 The equation was obtained by forcing the fit through zero. The coefficient of variation (R2) for this correlation is 0.9948.6. Apparatus6.1 Mini-Rotary Viscometer, ViscometeranAn apparatus tha
30、t consists of one or more viscometric cells in a temperaturecontrolled aluminum block. Each cell, when fitted with the specified rotor, becomes a calibrated rotor-stator set. Rotation of therotor is achieved by an applied load acting through a string wound around the rotor shaft. The top bearing pla
31、te is fitted withlocking pins for holding the rotors stationary. Time of rotation is measured electronically by a device attached to the timing wheel.NOTE 1The rotors for use with this test method can be distinguished from the rotors used for other mini-rotary viscometer test methods by the whiterot
32、or and the white band on the upper half of the shaft. The white band provides rotor identification while the rotor is in the cell.6.1.1 The mini-rotary viscometric cell for this procedure has the following typical dimensions:Diameter of rotor 15.0 mmLength of rotor 20.0 mmInside diameter of cell 19.
33、0 mmRadius of shaft 3.18 mmRadius of string 0.10 mm6.2 Weight, WeightforFor applying mass. Weights are to be in increments of 2.5 g 6 1 %. A minimum of eight weightsegments will be needed for the measurements defined in this test method.6.3 Temperature Control System , SystemthatThat will regulate t
34、he samples in the cells according to the cooling programdescribed in Table X1.1 and within the tolerances specified in the table.6.4 Thermometers, Temperature Measuring Device for measuring the temperature of the block.Use either a calibrated DCTdescribed in 6.4.1 Two are required, one graduatedor l
35、iquid-in-glass thermometers described in 6.4.2from at least +40 to 90C in3 SAE Paper 1999013672, “Viscosity of Drive-Line Lubricants by a Special Mini-Rotary Viscometer Technique.”Available from Society ofAutomotive Engineers, 400Commonwealth Dr., Warrendale, PA 15096-0001.D6821 1231C subdivisions,
36、and one that has at least a two degree graduated range around the final test temperature in 0.2C subdivisions.Other thermometric devices of equal or greater accuracy and resolution may be used The DCT or the calibrated low temperatureliquid-in-glass thermometer shall be used as the thermometer for t
37、emperature measurement independent of the instrumentstemperature control, and shall be located in the thermowell.NOTE 2The display device and sensor must be correctly paired. Incorrect pairing will result in temperature measurement errors and possiblyirreversible damage to the electronics of the dis
38、play.6.4.1 A DCT shall meet the following:(1) A range from -45 to 100C with a display resolution to at least 0.01 C.(2) The only acceptable sensors are a resistance temperature device (RTD), such as a platinum resistance thermometer (PRT)or a thermistor that are either glass or metal sheathed.(3) Fo
39、r metal sheathed probe, use a 3 mm diameter probe with a sensing element that is less than 30 mm in length; a metalsheathed probe requires a thermowell sleeve measuring 6 mm outside diameter by 58 mm long with a hole in the center toaccommodate the probe. For a glass sheathed probe, use a probe 6 mm
40、 in diameter containing a sensing element less than 12 mmin length.(4) A combined (display and probe) minimum accuracy of 650 mK (0.05C).(5) A response time of less than or equal to 25 s as defined in Specification E1137.(6) A drift of less than 50 mK (0.05C) per year.(7) Error of less than 50 mK (0
41、.05C) over the range of intended use.(8) The DCT shall have a report of temperature calibration from a calibration laboratory with demonstrated competency intemperature calibration which is traceable to a national calibration laboratory or metrology standards body.(9) The DCT shall be calibrated ove
42、r a range from -40 to 85C with at least 4 data points evenly distributed over the rangeof -40 to -1C. The test report shall include the calibration data.6.4.1.1 The DCT calibration shall be checked at least annually by either measuring the ice point or against a referencethermometer in a constant te
43、mperature bath at the prescribed immersion depth to ensure compliance with 6.4.1 (6 and 7).NOTE 3When a DCTs calibration drifts in one direction over several calibration checks, that is, ice point, it may be an indication of deteriorationof the DCT.6.4.2 Two liquid in glass thermometers are required
44、. One shall be a calibrated 76 mm partial immersion thermometer with ascale from +5C to 1 degree lower than the lowest test temperature in 0.2C subdivisions. For test temperatures less than -35C,use a liquid-in-glass thermometer with at least a scale range of 2 degrees Celsius in 0.2C subdivisions.
45、The second thermometershall be a 76 mm partial immersion thermometer graduated from at least +40 to 90C in 1C subdivisions.6.4.2.1 Calibration CheckVerify the low temperature thermometer at least annually against a reference thermometer in aconstant temperature bath or in an ice bath. The thermomete
46、r is to be insert to its immersion depth. If using an ice bath, the icepoint reading is to be taken within 60 min after the thermometer has been at test temperature for at least 3 min. If the correctedtemperature reading deviates from the reference thermometer or the ice point then repeat this calib
47、ration check. If the thermometerdeviates from the reference value on two successive checks then a full thermometer recalibration is needed.6.4.2.2 RecalibrationA complete recalibration of the liquid-in-glass thermometer, while permitted, is not necessary in orderto meet the accuracy ascribed to liqu
48、id-in-glass thermometers design until the thermometers corrected measured temperaturedeviates from the reference thermometer or ice point by one scale division, or until five years has elapsed since the last fullcalibration.6.5 Time/Temperature Recording Device, DevicesuchSuch as a chart recorder or
49、 data logger to verify that the correct coolingof the samples has been accomplished.7. Reagents and Materials7.1 Calibration Oil, a low cloud-point fluid of approximately 60 000 mPas viscosity at 25C for calibration of the viscometriccells.7.2 Oil Solvent, commercial heptanes or similar solvent for the test fluids that evaporates without leaving a residue.(WarningFlammable.)7.3 AcetoneA technical grade of acetone is suitable provided it does not leave a residue upon evaporation. (WarningFlammable.)8.
