1、Designation: D6821 12D6821 14Standard 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 4040 C to 10C10 C after a prescribed preheat andcontrolled cooling to the final test temperature. The precision is stated for test temperatures from -4040 C to -26C.26 C.1.2 The applicabili
4、ty of this particular 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 seco
5、nd (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 use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applic
6、ability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2983 Test Method for Low-Temperature Viscosity of Lubricants Measured by Brookfield ViscometerD3829 Test Method for Predicting the Borderline Pumping Temperature of Engine OilD4684 Test Method for Determination
7、 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 as a Reference TemperatureE644 Test Methods for Testing
8、 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 LaboratoriesISO Guide 34 General Requirements for the Comp
9、etence 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 Thermometer (DCT), nan electronic device consisting of a digital display and associated temperaturesensing probe.3.1.2
10、.1 Discussion1 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 Nov. 1, 2012July 1, 2014. Published April 2013July 2014. Originally ap
11、proved in 2002. Last previous edition approved in 20072012 asD682102(2007).D6821 12. DOI: 10.1520/D6821-12.10.1520/D6821-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, re
12、fer 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 intended only to provide the user of an ASTM standard an indica
13、tion 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 versionof the standard as published by ASTM is to be con
14、sidered 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 States1This device consists of a temperature sensor connected to a measuring instrument; this inst
15、rument 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 contact with the material whose temperature is being measured.This device i
16、s sometimes referred to as a digital thermometer.NOTE 1Portable electronic thermometers (PET) is an acronym sometimes used to refer to a subset of the devices covered by this definition.3.1.3 Newtonian oil or fluid, nan oil or fluid that at a given temperature exhibits a constant viscosity at all sh
17、ear 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.3.1.5.1 DiscussionFor a Newtonian fluid in a concentric cylinder r
18、otary 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 2Rs2Rs22Rr2 (1) 52Rs2Rs22Rr2 (1)Gr 5 4piRs2tRs22Rr2! (2) 5 4piRs2tRs22Rr2! (2)where:Gr = shear rate at t
19、he surface of the rotor in reciprocal seconds, s-1, = 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
20、(3) 533t (3)3.1.6 shear stress, 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 Tr2pi
21、Rr2 h 3109 (5) 5 Tr2piRr2 h 3109 (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, andD6821 142 = shear stress at the rotor surface, Pa, andh = height of the rotor face, mm.For the dime
22、nsions given in 6.1.1,Tr 532 M 31026 (6)Sr 54.5 M (7) 54.5 M (7)3.1.7 viscosity, nthe ratio between the applied shear stress 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
23、viscosity is the pascal second Pas. Thesubmultiple unit is millipascal seconds (mPas).3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration oils, nthose oils that establish the instrumentsan instruments reference framework of apparent viscosityversus speed (angular velocity), speed, f
24、rom which the apparent viscosities of test oils are determined.3.2.1.1 DiscussionCalibration oils, which are essentially Newtonian fluids, are available commercially and are described in 7.1.3.2.2 test oil, nany oil for which the apparent viscosity is to be determined by this test method.3.2.3 yield
25、 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 50C50 C for a specified time and then cooled at a programmed rate (see Table X1.1)
26、tothe final 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 Use5.1 Visco
27、sity 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 as the
28、y 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 performance of d
29、rive 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 length
30、 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 obtained in
31、 Test Method D2983.4 Thecorrelation obtained is:V 50.9413VD2983 (8)V 50.9413VD2983 (8)where:V = the apparent viscosity measured by this test method, and4 SAE Paper 1999013672, “Viscosity of Drive-Line Lubricants by a Special Mini-Rotary Viscometer Technique.”Available from Society ofAutomotive Engin
32、eers, 400Commonwealth Dr., Warrendale, PA 15096-0001.D6821 143VD2983 = 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 ViscometerAn appar
33、atus 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 anapplied load acting through a string wound around the rotor shaft. The top bea
34、ring plate is fitted with locking pins for holding therotors 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
35、whiterotor 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
36、cell 19.0 mmRadius of shaft 3.18 mmRadius of string 0.10 mmDiameter of rotor 15.00 mm 0.08 mmLength of rotor 20.00 mm 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 mi
37、nimum of eight weight segments will beneeded for the measurements defined in this test method. One segment will be the 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 i
38、n the table.6.4 Temperature Measuring DeviceUse either a calibrated DCT DCT meeting the requirements described in 6.4.1 orliquid-in-glass thermometers described in 6.4.2. The A calibrated DCT or the calibrated low temperature liquid-in-glassthermometer shall be used as the thermometer for temperatur
39、e measurement below 25 C independent of theinstrumentsinstruments temperature control, and shall be located in the thermowell.NOTE 2The DCT display device and sensor must be correctly paired. Incorrect pairing will result in temperature measurement errors and possiblyirreversible damage to the elect
40、ronics of the display.6.4.1 Digital Contact Thermometer Requirements: ACriteria Minimum RequirementsDCT Guide E2877, Class BTemperature range 45 C to 100 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 ele
41、ment 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 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 d
42、efined 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 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 R
43、eport From a calibration laboratory with demonstrated competency in temperature calibration which is traceable to a na-tional calibration laboratory or metrology standards bodyDCT shall meet the following:(1) A range from -45 to 100C with a display resolution to at least 0.01 C.(2) The only acceptab
44、le 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) For metal sheathed probe, use a 3 mm diameter probe with a sensing element that is less than 30 mm in length; a metalsheathed probe require
45、s 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 in diameter containing a sensing element less than 12 mmin length.(4) A combined (display and probe) minimum accuracy of 650 mK (0.05C).
46、(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 (0.05C) over the range of intended use.D6821 144(8) The DCT shall have a report of temperature calibration from a calibration laboratory wi
47、th demonstrated competency intemperature calibration which is traceable to a national calibration laboratory or metrology standards body.(9) The DCT shall be calibrated over a range from -40 to 85C with at least 4 data points evenly distributed over the rangeof -40 to -1C. The test report shall incl
48、ude the calibration data.NOTE 3With 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 shalldriftshall be checked at least annually by either measuring the ice point or agai
49、nst a referencethermometer in a constant temperature bath at the prescribed immersion depth to ensure compliance with 6.4.1 (6 . With respectto an ice bath, Practice E563and 7). provides guidance on the preparation and use of an ice bath. However, for this use, variancefrom the specific steps, such as water source, is permitted provided preparation is consistent. The basis for the variance is due tothe ice bath reference being used for tracking change in calibration not verific
