1、Designation: D4684 14D4684 17Standard Test Method forDetermination of Yield Stress and Apparent Viscosity ofEngine Oils at Low Temperature1This standard is issued under the fixed designation D4684; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This
3、 test method covers the measurement of the yield stress and viscosity of engine oils after cooling at controlled rates overa period exceeding 45 h to a final test temperature between 10 C and 40 C. The precision is stated for test temperatures from40 C to 15 C. The viscosity measurements are made at
4、 a shear stress of 525 Pa over a shear rate of 0.4 s1to 15 s1. Theviscosity as measured at this shear stress was found to produce the best correlation between the temperature at which the viscosityreached a critical value and borderline pumping failure temperature in engines.1.2 This test method con
5、tain two procedures: Procedure A incorporates several equipment and procedural modifications fromTest Method D468402 that have shown to improve the precision of the test, while Procedure B is unchanged from Test MethodD468402. Additionally, Procedure A applies to those instruments that utilize therm
6、oelectric cooling technology or directrefrigeration technology of recent manufacture for instrument temperature control. Procedure B can use the same instruments usedin Procedure A or those cooled by circulating methanol.1.3 Procedure A of this test method has precision stated for a yield range from
7、 less than 35 Pa to 210 Pa and apparent viscosityrange from 4300 mPas to 270 000 mPas. The test procedure can determine higher yield stress and viscosity levels.1.4 This test method is applicable for unused oils, sometimes referred to as fresh oils, designed for both light duty and heavyduty engine
8、applications. It also has been shown to be suitable for used diesel and gasoline engine oils. The applicability topetroleum products other than engine oils has not been determined.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this sta
9、ndard.1.5.1 ExceptionThis test method uses the SI based unit of milliPascal second (mPas) for viscosity which is equivalent to,centiPoise (cP).1.6 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 standa
10、rd to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Dev
11、elopment of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3829 Test Method for Predicting the Borderline Pumping Temperature of Engine OilE563 Practice for Preparation
12、and Use of an Ice-Point Bath as a Reference TemperatureE644 Test Methods for Testing Industrial Resistance ThermometersE1137 Specification for Industrial Platinum Resistance ThermometersE2877 Guide for Digital Contact Thermometers1 This test method is under the jurisdiction ofASTM Committee D02 on P
13、etroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved July 1, 2014May 1, 2017. Published August 2014May 2017. Originally approved in 1987. Last previous edition approved in 20122014 asD4684 12.D4684 14. DOI:
14、 10.1520/D4684-14.10.1520/D4684-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an AS
15、TM 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 technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In a
16、ll 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 standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 ISO S
17、tandard:3ISO 17025 General Requirements for the Competence of Testing and Calibration LaboratoriesISO Guide 34 General Requirements for the Competence of Reference Material Producers3. Terminology3.1 Definitions:3.1.1 apparent viscosity, nthe determined viscosity obtained by use of this test method.
18、3.1.2 Digital Contact Thermometerdigital contact thermometer (DCT), nan electronic device consisting of a digital displayand associated temperature sensing probe.3.1.2.1 DiscussionThis device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperatu
19、re-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 is output. This digital output
20、 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 1Portable electronic thermometers (PET) is an acronym sometimes used to refer to a subset of the devices cover
21、ed 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 at a given temperature exhibits a constant viscosity at all shear rates or shearstresses.3.1.4 non-Newton
22、ian 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. For a Newtonian fluid in a concentric cylinder rotary viscometer in whichthe shear stress is measured at the
23、 inner cylinder surface (such as this apparatus, described in 6.1), and ignoring any end effects,the shear rate is given as follows: 5 2!Rs2Rs22Rr2 (1)5 4pi!Rs2t Rs22Rr2! (2)where: = shear rate at the surface of the rotor in reciprocal seconds, s1, = angular velocity, rad/s,Rs = stator radius, mm,Rr
24、 = rotor radius, mm, andt = time in seconds for one revolution of the rotor.For the specific apparatus being described in 6.1.1, 563/t (3)3.1.6 shear stress, nthe motivating force per unit area for fluid flow. For the rotary viscometer being described, the rotorsurface is the area under shear or the
25、 shear area.Tr 59.81 M Ro1Rt!31026 (4) 5 Tr2pi!Rr2 h 3109 (5)where:Tr = torque applied to rotor, Nm,M = applied mass, g,Ro = radius of the shaft, mm,Rt = radius of the string, mm,3 Available from International Organization for Standardization (ISO), 1 rue de Varemb, Case postale 56, CH-1211, Geneva
26、20, Switzerland, http:/www.iso.ch.D4684 172 = shear stress at the rotor surface, Pa, andh = height of the rotor, mm.For the dimensions given in 6.1.1,Tr 531.7 M 31026 (6) 53.5 M (7)3.1.7 viscosity, nthe ratio between the applied shear stress and rate of shear, sometimes called the coefficient of dyn
27、amicviscosity. This value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the Pascal second Pas.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration oils, nthose oils that establish an instruments reference framework of apparent viscosity versus
28、 speed, fromwhich the apparent viscosities of test oils are determined.3.2.2 cell constant, nthe ratio of the calibration fluid viscosity to the time required to complete the first three measuredrevolutions of the rotor.3.2.3 test oil, nany oil for which the apparent viscosity and yield stress are t
29、o be determined by this test method.3.2.4 unused oil, nan oil which has not been used in an operating engine.3.2.5 used oil, nan oil which has been used in an operating engine.3.2.6 yield stress, nthe shear stress required to initiate flow. For all Newtonian fluids and many non-Newtonian fluids, the
30、yield stress is zero. An engine oil can have a yield stress that is a function of its low-temperature cooling rate, soak time, andtemperature.4. Summary of Test Method4.1 An engine oil sample is held at 80 C and then cooled at a programmed cooling rate to a final test temperature and held fora speci
31、fied time period. At the end of this period, a series of increasing low torques are applied to the rotor shaft until rotationoccurs to determine the yield stress, if any is exhibited. A higher torque is then applied to determine the apparent viscosity of thesample.5. Significance and Use5.1 When an
32、engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test,a fresh engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relativelyrapid cooling to the final test temperature. Th
33、ese laboratory test results have predicted as failures the known engine oils that havefailed in the field because of lack of oil pumpability.4 These documented field failing oils all consisted of oils normally tested at25 C. These field failures are believed to be the result of the oil forming a gel
34、 structure that results in either excessive yield stressor viscosity of the engine oil, or both.5.2 Cooling Profiles:5.2.1 For oils to be tested at 20 C or colder, Table X1.1 applies. The cooling profile described in Table X1.1 is based on theviscosity properties of theASTM Pumpability Reference Oil
35、s (PRO). This series of oils includes oils with normal low-temperatureflow properties and oils that have been associated with low-temperature pumpability problems (1-5).5 Significance for the 35 Cand 40 C temperature profiles is based on the data collected from the “Cold Starting and Pumpability Stu
36、dies in ModernEngines” conducted by ASTM (6,7).5.2.2 For oils to be tested at 15 C or 10 C, Table X1.2 applies. No significance has been determined for this temperatureprofile because of the absence of appropriate reference oils. Similarly, precision of the test method using this profile for the 10
37、Ctest temperature is unknown. The temperature profile of Table X1.2 is derived from the one in Table X1.1 and has been movedup in temperature, relative to Table X1.1, in consideration of the expected higher cloud points of the viscous oils tested at 15 Cand 10 C.6. Apparatus6.1 Mini-Rotary Viscomete
38、rAn apparatus that consists of one or more viscometric cells in a temperature-controlled blockmade of a metallic material with high thermal conductivity. Each cell contains a calibrated rotor-stator set. The rotor shall havea crossbar near the top of the shaft extending in both directions far enough
39、 to allow the locking pin (6.6) to stop rotation atsuccessive half turns. Rotation of the rotor is achieved by an applied force acting through a string wound around the rotor shaft.6.1.1 The mini-rotary viscometric cell has the following dimensions:4 Pumpability Reference Oils (PRO) 21 through 29.5
40、The boldface numbers in parentheses refer to the references at the end of this standard.D4684 173Diameter of rotor 17.06 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 mm6.1.2 Cell CapA cover inserted into the top
41、 of the viscometer cell to minimize room air circulation into the cells is requiredfor thermometrically cooled instruments. The cell cap is a stepped cylinder 38 mm 6 1 mm in length made of a low thermalconductivity material, for example, thermoplastic such as acetyl copolymers that have known solve
42、nt resistivity and are suitablefor use between the temperature ranges of this test method. The top half is 28 mm 6 1 mm in diameter and the bottom half is 19mm in diameter with a tolerance consistent with the cell diameter. The tolerance on the bottom half is such that it will easily fitinto cell bu
43、t not allow cap to contact rotor shaft. The piece has a center bore of 11 mm 6 1 mm. The cap is made in two halvesto facilitate placement in the top of the cell.6.1.2.1 Cell caps shall not be used in the direct refrigeration instruments, since such use would block the flow of cold, dry airinto the s
44、tators to keep them frost-free.6.2 Weights:6.2.1 Yield Stress MeasurementA set of nine disks and a disk holder, each with a mass of 10 g 6 0.1 g.6.2.2 Viscosity MeasurementA mass of 150 g 6 1.0 g.6.3 Temperature Control SystemRegulates the mini-rotary viscometer block temperature in accordance with
45、the temperaturerequirements described in Table X1.1 or Table X1.2.6.3.1 Temperature ProfileThe temperature profile is fully described in Table X1.1 and Table X1.2.6.4 Temperature Measuring DeviceUse either a DCT meeting the requirements described in 6.4.1 or liquid-in-glassthermometers described in
46、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 display device and sensor must be correctly pai
47、red. 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 E2877 Class BTemperature range 45 C to 100 CDisplay resolution 0.1 C minimum, prefera
48、bly 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 thermowellsleeve, 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 lengthDi
49、splay accuracy 50 mK (0.05 C) for combined probe and sensorResponse time less than or equal to 25 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 Range 40 C to 85 CCalibration Data 4 data points evenly distributed over the range of 40 C to 1 C and included in calibrationreport.Calibration Report From a calibration laboratory with demonstrated competency in
