ASTM D4741 Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
1. Scope
1.1 This test method covers the laboratory determination of the viscosity of oils at 150°C and 1 x 10(6)s(-1) using Ravenfield high shear rate tapered-plug viscometer models BE or BS. This test method may readily be adapted to other conditions if required.
1.2 Newtonian calibration oils are used to adjust the working gap and for calibration of the apparatus. These calibration oils cover a range from approximately 1.8 to 5.9 cP (mPa.s) at 150°C. This test method should not be used for extrapolation to higher viscosities than those of the Newtonian calibration oils used for calibration of the apparatus.
1.3 A non-Newtonian reference oil is used to check that the working conditions are correct. The exact viscosity appropriate to each batch of this oil is established by testing on a number of instruments in different laboratories. The agreed value for this check oil may be obtained by reference to the chairman of the CEC Surveillance Group for the Ravenfield tapered-plug viscometer method L-36 or to the distributor.
1.4 Applicability to products other than engine oils has not been determined in preparing this method.
1.5 This test method uses the centipoise (cP) as the unit of viscosity. For information, the equivalent SI unit, the millipascal second (mPa.s) is shown in parenthesis.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D91 Test Method for Precipitation Number of Lubricating Oils
D4683 Test Method for Measuring Viscosity at High Shear Rate and High Temperature by Tapered Bearing Simulator
D5481 Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer
2.2 Coordinating European Council (CEC) Standard:
L-36 Test Method for the Measurement of Lubricant Dynamic Viscosity under Conditions of High Shear
2.3 Institute of Petroleum (IP) Standard:
IP-370 Test Method for the Measurement of Lubricant Dynamic Viscosity under Conditions of High Shear using the Ravenfield Viscometer
3. Terminology
3.1 Definitions:
3.1.1 apparent viscosity - the determined viscosity obtained by this test method.
3.1.2 density - the mass per unit volume. In the SI, the unit of density is the kg/m3, but for practical use a submultiple is more convenient. The g/cm3 is 103 kg/m3 and is customarily used.
3.1.3 kinematic viscosity - the ratio of the viscosity to the density of a liquid. It is a measure of the resistance of flow of a liquid under gravity. In the SI, the unit of kinematic viscosity is the metre squared per second; for practical use, a submultiple (millimetre squared per second) is more convenient. The centistokes (cSt) is 1 mm2/s and is customarily used.
3.1.4 Newtonian oil or fluid - an oil or fluid which at a given temperature exhibits a constant viscosity at all shear rates or shear stresses.
3.1.5 non-Newtonian oil or fluid - an oil or fluid which exhibits a viscosity that varies with changing shear stress or shear rate.
3.1.6 shear rate - the velocity gradient in fluid flow. The SI unit for shear rate is the reciprocal second (s(-1)).
3.1.7 shear stress - the motivating force per area for fluid flow. The area is the area of shear. In the SI, the unit for shear stress is the Pascal (Pa).
3.1.8 viscosity - the ratio between the applied shear stress and rate of shear. It is sometimes called the coefficient of dynamic viscosity. This coefficient is thus a measure of the resistance to flow of the liquid. In the SI, the unit of viscosity is the pascal second (Pa.s); for practical use, a submultiple, millipascal second (mPa.s), is more convenient. The centipoise (cP) is 1 mPa.s and is customarily used.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 calibration oils - Newtonian oils used to establish the reference framework of viscosity versus torque from which is determined the test oil viscosity.
3.2.2 non-Newtonian check oil - non-Newtonian oil used to check that the gap or distance between the rotor and stator will produce the desired operating shear rate of 1 x 10(6)s(-1).
3.2.3 test oil - any oil for which apparent viscosity is to be determined.
