ASTM_D_4624_-_93_1998.pdf

Designation:D 4624 93(Reapproved 1998)An American National StandardStandard Test Method forMeasuring Apparent Viscosity by Capillary Viscometer atHigh-Temperature and High-Shear Rates1This standard is issued under the fixed designation D 4624;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.INTRODUCTIONSeveral different configurations of capillary viscometers have been successfully used for measuringthe viscosity of engine oils at the high-shear rates and high temperatures that occur in engines.Thistest method evolved from a cooperative program that included a wide variety of viscometer designsand procedures.Therefore,this test method is very general but its precision has not been establishedfor any viscometer designs or procedures not evaluated in the cooperative program.1.Scope1.1 This test method covers the measurement of hightem-perature high-shear viscosity at 150C.The shear rate for thistest method corresponds to an apparent shear rate at the wall of106s1.This is the shear rate at the wall calculated for aNewtonian oil.For non-Newtonian oils,the actural shear rateat the wall will vary from this value.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 1217 Test Method for Density and Relative Density(Specific Gravity)of Liquids by Bingham Pycnometer2D 4683 Test Method for Measuring Viscosity at High Tem-perature and High Shear Rate by Tapered Bearing Simu-lator3D 4741 Test Method for Measuring Viscosity at High Tem-perature and High Shear Rate by Tapered Plug Viscom-eter33.Terminology3.1 Definitions:3.1.1 viscositythe ratio between shear stress and shear rateat the same location.It is sometimes called the coefficient ofviscosity,or the dynamic viscosity.It is a measure of a fluidsresistance to flow.In the SI,the unit of viscosity is a pascalsecond(Pas);for practical use a submultiple(millipascalsecond,mPas)is more convenient.The centipoise(cP)is 1mPas and is often used.3.1.2 apparent viscositythe determined viscosity obtainedby this test method.3.1.3 kinematic viscositythe ratio of the viscosity to thedensity of the fluid.It is a measure of a fluids resistance toflow under the force of gravity.In the SI,the unit of kinematicviscosity is the metre squared per second(m2/s);for practicaluse,a submultiple(millimetre squared per second,mm2/s)ismore convenient.The centistoke(cSt)is 1 mm2/s and is oftenused.3.1.4 Newtonian oil or fluidan oil or fluid that exhibits aconstant viscosity at all shear rates or shear stresses.3.1.5 non-Newtonian oil or fluidan oil or fluid that exhib-its a viscosity that varies with changing shear rate or shearstress.3.1.6 shear ratethe spatial gradient of velocity in laminarflow;the derivative of velocity with respect to distance in adirection perpendicular to the direction of flow.The derivedunit of shear rate is velocity divided by length.With time inseconds and with consistent units of length,shear rate becomesreciprocal seconds,or s1.In a capillary,the significant shearrate for a Newtonian fluid is as follows:S 5 4Q/pR3(1)where:S5 shear rate,s1,Q5 flow rate,andR5 capillary radius in consistent units.3.1.7 shear stressforce per area of fluid in the direction offlow.In a capillary viscometer,the significant shear stress is themaximum shear stress at the wall,that is,the total force acting1This test method is under the jurisdiction of ASTM Committee D-2 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.07 on Flow Properties.Current edition approved March 15,1993.Published May 1993.Originallypublished as D 4624 86.Last previous edition D 4624 86e1.2Annual Book of ASTM Standards,Vol 05.01.3Annual Book of ASTM Standards,Vol 05.03.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.on the cross section of the capillary divided by the area of theinside surface of the capillary.The SI unit for shear stress is thepascal(Pa);for practical use in this application,a submultiple,the millipascal(mPa),may be used.Mathematically,the shearstress in a capillary viscometer is as follows:Z 5 PR/2L(2)where:Z5 shear stress,Pa,P5 pressure drop,Pa,R5 capillary radius,andL5 capillary length in consistent units.3.1.8 densitythe mass per unit volume.In the SI,the unitof density is the kilogram per metre cubed(kg/m3);the gramper cubic centimetre is often used.Density in units of g/cm3ismultiplied by 1000 to get density in units of kg/m3.3.2 Definit