1、Designation: D4684 17aD4684 18Standard 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 ca
2、se 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 Thi
3、s 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 a
4、t a shear stress of 525 Pa over a shear rate of 0.4 s1 to 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 c
5、ontain 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 the
6、rmoelectric 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 fr
7、om 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 engin
8、e 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 s
9、tandard.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 stan
10、dard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Prin
11、ciples for the Development 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 Practic
12、e for Preparation 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
13、Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved Dec. 1, 2017June 1, 2018. Published December 2017June 2018. Originally approved in 1987. Last previous edition approved in 2017 asD4684
14、 17.D4684 17a. DOI: 10.1520/D4684-17A.10.1520/D4684-18.2 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 d
15、ocument 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 technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions
16、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 standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Uni
17、ted States12.2 ISO Standard: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
18、of this test method.3.1.2 digital contact thermometer (DCT), nan electronic device consisting of a digital display and associated temperaturesensing probe.3.1.2.1 DiscussionThis device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-depe
19、ndent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output. This digitaloutput goes to a digital display and/or recording device that may be internal or external to the device. These devices are sometimesreferred to as “digital thermometers.”3.1.
20、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-Newtonian oil or fluid, nan oil
21、or fluid that at a given temperature exhibits a viscosity that varies with changingshear stress or shear rate.3.1.5 viscosity, nthe ratio between the applied shear stress and rate of shear, sometimes called the coefficient of dynamicviscosity. This value is thus a measure of the resistance to flow o
22、f the liquid. The SI unit of viscosity is the Pascal second Pas.3.2 Definitions:Definitions of Terms Specific to 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
23、 determined.3.2.2 apparent viscosity,cell constant, nthe determined viscosity obtained by use of this test method.ratio of the calibrationfluid viscosity to the time required to complete the first three measured revolutions of the rotor.3.1.2 digital contact thermometer (DCT), nan electronic device
24、consisting of a digital 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,
25、and provides a digital output. This digitaloutput goes to a digital display and/or recording device that may be internal or external to the device. These devices are sometimesreferred to as “digital thermometers.”3.1.2.2 DiscussionPET is an acronym for portable electronic thermometers, a subset of d
26、igital 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-Newtonian oil or fluid, nan oil or fluid that at a given temperature exhibits a viscosity that varies with changing
27、shear stress or shear rate.3.2.3 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 inner cylinder surface (such as this apparatus, described in 6.1), and ignoring any end effects,the shear ra
28、te is given as follows:3 Available from International Organization for Standardization (ISO), 1 rue de Varemb, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.D4684 182 5 2!Rs2Rs22Rr2 (1)5 4pi!Rs2t Rs22Rr2! (2)where: = shear rate at the surface of the rotor in reciprocal seconds,
29、s1, = angular velocity, rad/s,Rs = stator radius, mm,Rr = 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)3.2.3.1 DiscussionFor a Newtonian fluid in a concentric cylinder rotary viscometer in which the shear stres
30、s is measured at the 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 =
31、stator radius, mm,Rr = 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)3.2.4 shear stress, nthe motivating force per unit area for fluid flow. For the rotary viscometer being described, the rotorsurface is the are
32、a under shear or the 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, = shear stress at the rotor surface, Pa, andh = height of the rotor, mm.For the dimensions given in
33、6.1.1,Tr 531.7 M 31026 (6) 53.5 M (7)3.2.4.1 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 Tr2pi!Rr2 h 3109 (5)D4684 183where:Tr = torque applie
34、d to rotor, Nm,M = applied mass, g,Ro = radius of the shaft, mm,Rt = radius of the string, mm, = 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)3.2.5 test oil, nany oil for which the apparent viscosity and yield
35、stress are to be determined by this test method.3.2.6 unused oil, nan oil which has not been used in an operating engine.3.2.7 used oil, nan oil which has been used in an operating engine.3.2.8 viscosity, yield stress, nthe ratio between the applied shear stress and rate of shear, sometimes called t
36、he coefficient ofdynamic viscosity. This value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the Pascal secondPas.shear stress required to initiate flow.3.2.8.1 DiscussionFor all Newtonian fluids and many non-Newtonian fluids, the yield stress is zero. An oil
37、 can have a yield stress that is a functionof its low-temperature cooling rate, soak time, and temperature. Yield stress measurement by this test method determines onlywhether the test oil has a yield stress of at least 35 Pa; a yield stress below 35 Pa is considered to be insignificant for engine o
38、ils.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 speed, fromwhich the apparent viscosities of test oils are determined.3.2.2 cell constant, nthe ratio of the calibration fluid vis
39、cosity 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 to 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 oi
40、l 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, theyield stress is zero. An engine oil can have a yield stress that is a function of its low-temperature cooling rate, soak time, andt
41、emperature.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 specified time period. At the end of this period, a series of increasing low torques are applied to the rotor shaft until rotationoccurs
42、 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 engine oil is cooled, the rate and duration of cooling can affect its yield stress and viscosity. In this laboratory test,a fresh e
43、ngine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relativelyrapid cooling to the final test temperature. These laboratory test results have predicted as failures the known engine oils that havefailed in the field because of lack of oil pu
44、mpability.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 structure that results in either excessive yield stressor viscosity of the engine oil, or both.5.2 Cooling Profiles:4 Pumpability
45、Reference Oils (PRO) 21 through 29.D4684 1845.2.1 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 Oils (PRO). This series of oils includes oils with normal low-temperatureflo
46、w 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 Studies in ModernEngines” conducted by ASTM (6, 7).5.2.2 For oils to be test
47、ed 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 Ctest temperature is unknown. The temperature profile of Table X1.2 is d
48、erived 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 ViscometerAn apparatus that consists of one or more viscometric cells in a temper
49、ature-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 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 dime
