1、Designation: D6821 14D6821 17Standard 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 adoption or, in the c
2、ase 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*1.1 This test method covers the measurement of the viscosity of drive line lubricants (gear
3、oils, automatic transmission fluids,and so forth) with a constant shear stress viscometer at temperatures from 40 C to 10 C after a prescribed preheat and controlledcooling to the final test temperature. The precision is stated for test temperatures from 40 C to 26 C.1.2 The applicability of this pa
4、rticular test method to petroleum products other than drive line lubricants has not beendetermined.1.3 The values stated in SI units are to be regarded 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
5、 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 use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of re
6、gulatorylimitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Orga
7、nization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D2983 Test Method for Low-Temperature Viscosity of Automatic Transmission Fluids, Hydraulic Fluids, and Lubricants usinga Rotational ViscometerD3829 Test Method for Predicting the Borderline Pumping Tempe
8、rature 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 Oils at Low TemperatureE563 Practice for Preparation and Use of an Ice-Point Bath
9、as a Reference TemperatureE644 Test Methods for Testing Industrial Resistance ThermometersE1137 Specification for Industrial Platinum Resistance ThermometersE2877 Guide for Digital Contact Thermometers2.2 ISO Standards:3ISO 17025 General Requirements for the Competence of Testing and Calibration Lab
10、oratoriesISO Guide 34 General Requirements for the Competence of Reference Material Producers3. Terminology3.1 Definitions:3.1.1 apparent viscosity, nthe determined viscosity obtained by the use of this test method.3.1.2 Digital Contact Thermometerdigital contact thermometer (DCT), nan electronic de
11、vice consisting of a digital displayand associated temperature sensing probe.1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved July 1
12、, 2014May 1, 2017. Published July 2014June 2017. Originally approved in 2002. Last previous edition approved in 20122014 asD6821 12.D6821 14. DOI: 10.1520/D6821-14.10.1520/D6821-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org
13、. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.This document is not an ASTM standard and is intend
14、ed 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 technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current
15、 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 standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2.1 DiscussionThis device cons
16、ists 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 digital output or display,or both, of the temperature. The temperature sensing probe is in
17、contact with the material whose temperature is being measured.This device is output. This digital output goes to a digital display and/or recording device that may be internal or external to thedevice. These devices are sometimes referred to as a“digital digital thermometer.thermometers.”NOTE 1Porta
18、ble electronic thermometers (PET) is an acronym sometimes used to refer to a subset of the devices covered by this definition.3.1.2.2 DiscussionPET is an acronym for portable electronic thermometers, a subset of digital contact thermometers (DCT).3.1.3 Newtonian oil or fluid, nan oil or fluid that a
19、t a given temperature exhibits a constant viscosity at all shear rates or shearstresses.3.1.4 non-Newtonian oil or fluid, nan oil or fluid that at a given temperature exhibits a viscosity that varies with changingshear stress or shear rate.3.1.5 shear rate, nthe velocity gradient in fluid flow.3.1.5
20、.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: 5 2Rs2Rs22Rr2 (1) 5 4piRs2tRs22Rr2! (2)where: =
21、 shear rate at the surface of the rotor in reciprocal seconds, s-1, = angular velocity, rad/s, = 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, 533t (3)3.1.6 shear stress, nthe
22、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) 5 Tr2piRr2 h 3109 (5)where:Tr = torque applied
23、 to rotor, Nm,M = applied mass, g,Ro = radius of the shaft, mm,Rr = radius of the string, mm, = shear stress at the rotor surface, Pa, andh = height of the rotor face, mm.For the dimensions given in 6.1.1,D6821 172Tr 532 M 31026 (6) 54.5 M (7)3.1.7 viscosity, nthe ratio between the applied shear str
24、ess and rate of shear, sometimes called the coefficient of dynamicviscosity.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 Definitions of Terms Specific t
25、o This Standard:3.2.1 calibration oils, nthose oils that establish an instruments reference framework of apparent viscosity versus speed, fromwhich the apparent viscosities of test oils are determined.3.2.2 test oil, nany oil for which the apparent viscosity is to be determined by this test method.3
26、.2.3 yield stress, nthe shear stress required to initiate 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 50 C for a specified time and then cooled at a programmed rate (see Table
27、 X1.1) to thefinal test temperature and soaked at the final temperature for a defined period of time. 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.
28、1 Viscosity of drive line lubricants at low temperature is critical for both gear lubrication and the 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
29、 as they begin rotating and re-lubricating them as they continue to rotate. For automatictransmission 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 performan
30、ce of drive line lubricant flow characteristics was originally evaluated by the channel test.In this 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
31、 length of the pan after it had soaked at testtemperature for a specified time. The time it took the 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 obta
32、ined in Test Method D2983.4 Thecorrelation obtained is:V 50.9413VD2983 (8)where:V = the apparent viscosity 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)
33、 for this correlation is 0.9948.6. Apparatus6.1 Mini-Rotary ViscometerAn apparatus that consists of one or more viscometric cells in a temperature controlled aluminumblock. Each cell, when fitted with the specified rotor, becomes a calibrated rotor-stator set. Rotation of the rotor is achieved by an
34、applied load acting through a string wound around the rotor shaft. The top bearing plate is fitted with locking pins for holding therotors stationary. Time of rotation is measured electronically by a device attached to the timing wheel.6.1.1 The mini-rotary viscometric cell for this procedure has th
35、e following typical dimensions:4 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 173Diameter of rotor 15.00 mm 0.08 mmLength of rotor 20.00 mm
36、0.14 mmInside diameter of cell 19.07 mm 0.08 mmRadius of shaft 3.18 mm 0.13 mmRadius of string 0.1 mm6.2 WeightFor applying mass. Weights are to be in increments of 2.5 g 6 1 %. A minimum of eight weight segments will beneeded for the measurements defined in this test method. One segment will be the
37、 weight holder.6.3 Temperature Control SystemThat will regulate the samples in the cells according to the cooling program described inTable X1.1 and within the tolerances specified in the table.6.4 Temperature Measuring DeviceUse either a DCT meeting the requirements described in 6.4.1 or liquid-in-
38、glassthermometers described in 6.4.2. A calibrated DCT or calibrated low temperature liquid-in-glass thermometer shall be used as thethermometer for temperature measurement below 25 C independent of the instruments temperature control, and shall be locatedin the thermowell.NOTE 1The DCT display devi
39、ce and sensor must be correctly paired. Incorrect pairing will result in temperature measurement errors and possiblyirreversible damage to the electronics of the display.6.4.1 Digital Contact Thermometer Requirements:Criteria Minimum RequirementsDCT Guide E2877, Class BTemperature range 45 C to 100
40、CDisplay resolution 0.1 C minimum, preferably 0.01 CSensor type RTD, such as a PRT or thermistorSensor,metal sheathed3 mm O.D. with an sensing element less than 30 mm in length to be used with a thermowell sleeve, 6 mm O.D. 58 mm long with a 3 mm hole in center.Sensor,glass sheathed6 mm O.D. with a
41、sensing element less than 12 mm in lengthDisplay accuracy 50 mK (0.05 C) for combined probe and sensorResponse time less than or equal to 8 s as defined in Specification E1137Drift less than 50 mK (0.05 C) per yearCalibration Error less than 50 mK (0.05 C) over the range of intended use.Calibration
42、Range 40 C to 85 CCalibration Data 4 data points evenly distributed over the range of 40 C to 1 C and included in calibration report.Calibration Report From a calibration laboratory with demonstrated competency in temperature calibration which is traceable to a na-tional calibration laboratory or me
43、trology standards bodyNOTE 2With respect to DCT probe immersion depth, a procedure to determine minimum depth can be found in Guide E2877, Section 5.3, or TestMethods E644, Section 7.6.4.1.1 The DCT calibration driftshall be checked at least annually by either measuring the ice point or against a re
44、ferencethermometer in a constant temperature bath at the prescribed immersion depth to ensure compliance with 6.4.1. With respect toan ice bath, Practice E563 provides guidance on the preparation and use of an ice bath. However, for this use, variance from thespecific steps, such as water source, is
45、 permitted provided preparation is consistent. The basis for the variance is due to the ice bathreference being used for tracking change in calibration not verification.NOTE 3When a DCTs calibration drifts in one direction over several calibration checks, that is, ice point, it may be an indication
46、of deteriorationof the DCT.6.4.2 For liquid-in-glass thermometers, LiG, two are required. One LiG shall be a calibrated 76 mm partial immersionthermometer with a scale from +5 C to 1 degree lower than the lowest test temperature in 0.2 C subdivisions. For testtemperatures less than 35 C, use a liqui
47、d-in-glass thermometer with at least a scale range of 2 degrees Celsius in 0.2 Csubdivisions. The low temperature LiG thermometer(s) shall have a report of calibration showing the temperature deviation at eachcalibrated test temperature. The second LiG thermometer shall be a 76 mm partial immersion
48、thermometer graduated from at least+40 C to 90 C in 1 C subdivisions, which is used to verify the preheat temperature.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 thermometer is
49、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 calibration 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
