1、Designation: D4684 17D4684 17aStandard 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 45 h to a final test temperature between 10 C and 40 C. The precision is stated for test temperaturesfrom 40 C to 15 C. The viscosity measurements are m
4、ade at a shear stress of 525 Pa 525 Pa over a shear rate of 0.40.4 s1s1to 15 s15 s1. The viscosity as measured at this shear stress was found to produce the best correlation between the temperatureat which the viscosity reached a critical value and borderline pumping failure temperature in engines.1
5、.2 This test method contain 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 instrum
6、ents that utilize thermoelectric 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
7、 for a yield range from less than 35 Pa to 210 Pa 35 Pa to 210 Pa andapparent viscosity range from 4300 mPas to 270 000 mPas. 4300 mPas to 270 000 mPas. The test procedure can determinehigher yield stress and viscosity levels.1.4 This test method is applicable for unused oils, sometimes referred to
8、as fresh oils, designed for both light duty and heavyduty engine 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
9、 standard. No other units of measurement are included in this standard.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
10、 with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally
11、 recognized principles on standardizationestablished in the Decision on Principles 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
12、 for Predicting the Borderline Pumping Temperature of Engine OilE563 Practice 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 Digi
13、tal Contact Thermometers1 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 May 1, 2017Dec. 1, 2017. Published May 2017December 2017. O
14、riginally approved in 1987. Last previous edition approved in 20142017 asD4684 14.D4684 17. DOI: 10.1520/D4684-17.10.1520/D4684-17A.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume informa
15、tion, 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 technically possible to adequately depi
16、ct 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 standardCopyright ASTM Internation
17、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United 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 Def
18、initions:3.1.1 apparent viscosity, nthe determined viscosity obtained by use of this test method.3.1.2 digital contact thermometer (DCT), nan electronic device consisting of a digital display and associated temperaturesensing probe.3.1.2.1 DiscussionThis device consists of a temperature sensor conne
19、cted 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. This digitaloutput goes to a digital display and/or recording device that may be internal or external to the
20、device. These devices are sometimesreferred to as “digital thermometers.”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 a
21、t 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. For a Newtonian fluid in a concentric cylinder rotary vis
22、cometer 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 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,
23、= 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)3.1.6 shear stress, nthe motivating force per unit area for fluid flow. For the rotary viscometer being describ
24、ed, the rotorsurface is the area 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,
25、mm.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 17a2For 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 ra
26、te of shear, sometimes called the coefficient of dynamicviscosity. 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 instrume
27、nts 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 viscosity to the time required to complete the first three measuredrevolutions of the rotor.3.2.3 test oil, nany oil for
28、 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 oil which has been used in an operating engine.3.2.6 yield stress, nthe shear stress required to initiate flow. For all
29、 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, andtemperature.4. Summary of Test Method4.1 An engine oil sample is held at 80 C and then cooled at a programmed cooling
30、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 to determine the yield stress, if any is exhibited. A higher torque is then applied to determine the apparent viscos
31、ity 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 engine oil is slowly cooled through a temperature range where wax crystallization is known to occur, followed by relat
32、ivelyrapid 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 pumpability.4 These documented field failing oils all consisted of oils normally tested at25 C. These field failures ar
33、e 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: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 thevisco
34、sity properties of theASTM Pumpability Reference Oils (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 c
35、ollected from the “Cold Starting and Pumpability Studies 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, precis
36、ion of the test method using this profile for the 10 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
37、at 15 Cand 10 C.6. Apparatus6.1 Mini-Rotary ViscometerAn 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
38、 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 dimension
39、s:Diameter 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 mm4 Pumpability Reference Oils (PRO) 21 through 29.5 The boldface numbers in parentheses refer to the references at the end of this standard
40、.D4684 17a36.1.2 Cell CapA cover inserted into the top 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 38 mm 6 1 mm in length made ofa low thermal conductivity material, for exa
41、mple, thermoplastic such as acetyl copolymers that have known solvent resistivity andare suitable for use between the temperature ranges of this test method. The top half is 28 mm 6 1 mm a minimum of 25 mm indiameter and the bottom half is 19 mm 19 mm in diameter with a tolerance consistent with the
42、 cell diameter. The tolerance on thebottom half is such that it will easily fit into cell but not allow cap to contact rotor shaft. The piece has a center bore of 11 mm6 1 mm. The cap is made in two halves to facilitate placement in the top of the cell.6.1.2.1 Cell caps shall not be used in the dire
43、ct refrigeration instruments, since such use would block the flow of cold, dry airinto the stators 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. 10 g 6 0.1 g.6.2.2 Viscosity MeasurementA mass of 150 g 6 1.0
44、g.150 g 6 1.0 g.6.3 Temperature Control SystemRegulates the mini-rotary viscometer block temperature in accordance with 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 M
45、easuring DeviceUse either a DCT meeting the requirements described in 6.4.1 or liquid-in-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 25 C independent of the ins
46、truments temperature control, and shall belocated in the thermowell.NOTE 1The display device 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 requir
47、ements:Criteria Minimum RequirementsDCT 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 element less than 30 mm in length to be used with a thermowellsleeve, 6 mm
48、 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 25 s as defined in Specification E1137Drift less than 50 mK (0.05 C) per yearCal
49、ibration 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 temperature calibration which istraceable to a national calibration laboratory or metrology standards bodyNOTE 2With respect to DCT probe immersion depth, a procedure to
