ASTM D6616 Standard Test Method for Measuring Viscosity at High Shear Rate by Tapered Bearing Simulator Viscometer at 100°C
1. Scope
1.1 This test method covers the laboratory determination of the viscosity of engine oils at 100°C and 1·10(6)s(-1) using the Tapered Bearing Simulator (TBS) viscometer.
NOTE 1 - This test method is similar to Test Method D4683 which uses the same TBS viscometer to measure high shear viscosity at 150°C.
1.2 The Newtonian calibration oils used to establish this test method range from approximately 5 to 12 mPa·s (cP) at 100°C and either the manual or automated protocol was used by each participant in developing the precision statement. The viscosity range of the test method at this temperature is from 1 mPa·s (cP) to above 25 mPa·s (cP), depending on the model of TBS.
1.3 The non-Newtonian reference oil used to establish the shear rate of 1·10(6)s(-1) for this test method has a viscosity of approximately 10 mPa·s at 100°C.
1.4 Application to petroleum products other than engine oil has not been determined in preparing the viscometric information for this test method.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. This test method uses the milliPascal second (mPa·s) as the unit of viscosity. This unit is equivalent to the centiPoise (cP), which is shown in parentheses.
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 to determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D4683 Test Method for Measuring Viscosity at High Shear Rate and High Temperature by Tapered Bearing Simulator
D4741 Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
3. Terminology
3.1 Definitions:
3.1.1 density, n - mass per unit volume. In the SI, the unit of density is the kilogram per cubic metre. For practical use, the submultiple, gram per cubic centimetre, is more convenient. The density in gram per cubic centimetre is equal to 1/1000 the density in kg/m3.
3.1.2 Newtonian oil or fluid, n - an oil or fluid that at a given temperature exhibits a constant viscosity at all shear rates or shear stresses.
3.1.3 non-Newtonian oil or fluid, n - an oil or fluid that exhibits a viscosity that varies with changing shear stress or shear rate.
3.1.4 shear rate, n - the velocity gradient in fluid flow. The SI unit for shear rate is s(-1).
3.1.5 shear stress, n - the motivating force per unit area for fluid flow. The area is the area under shear. The SI unit for shear stress is the Pa.
3.1.6 viscosity, n - the ratio between the applied shear stress and the rate of shear. It is sometimes called the coefficient of dynamic viscosity. This coefficient is a measure of the resistance to flow of the liquid. In the SI, the unit of viscosity is the Pascal·second; often the milliPascal·second or its equivalent the centiPoise is found more convenient.
3.1.6.1 apparent viscosity, n - the viscosity of a non-Newtonian fluid at a given shear rate or shear stress determined by this test method.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 idling oil, n - an oxidatively stable Newtonian oil injected into the operating viscometer stator when the instrument is likely to be held for periods oftime greater than 30 min and up to two weeks at 100°C. Use of this oil prevents stator deposits from additives, which may decompose after longer exposure times in the operating viscometer and permits continuous operation of the viscometer without need to shut the instrument off.
3.2.2 Newtonian Reference Oil, n - a specially blended Newtonian oil that has the same viscosity at 100°C as the non-Newtonian reference oil of 3.2.3.
3.2.3 non-Newtonian reference oil , n - a specially formulated non-Newtonian oil, identified as NNR-10, having a selected apparent viscosity at 1·10(6)s(-1) shear rate. The oil is used to establish an operating gap between the rotor and stator which will produce 1·10(6)s(-1) shear rate when the rotor height is adjusted to give a torque output equivalent to that of the special reference oil described in 3.2.2.
3.2.4 reciprocal torque intersection, 1/Ti, n - the rotor position on the micrometer defined by the intersection of two straight lines generated by the reciprocal torque method using the Newtonian reference oil of 3.2.2 and non-Newtonian reference oil of 3.2.3. Reciprocal torque versus rotor height measurements on both oils gives straight lines whose intersection, 1/Ti, establishes the desired rotor position for operation at 1·10(6)s(-1) shear rate.
3.2.5 reference Newtonian calibration oils, n - specially chosen Newtonian oils used to determine the viscosity-torque relationship of the TBS viscometer at 100°C from which the viscosity of an unknown oil is calculated.
3.2.6 rotor height (rotor position), n - the vertical position of the rotor relative to the stator and measured by the platform micrometer.
3.2.6.1 stored rotor height (rotor position), n - the rotor position with the rotor 0.50 mm above the rubbing contact position (see 3.2.7) when the instrument is shut down.
3.2.7 rubbing contact position, n - the rotor height determined when the tapered rotor is lightly brought into contact with the similarly tapered stator.
3.2.8 test oil, n - any oil for which the apparent viscosity is to be determined by this test method.
