ASTM D4683 for measuring viscosity at high shear rate and high temperature
ASTM D4683 standard test method for measuring viscosity at high shear rate and high temperature by tapered bearing simulator
1. Scope
1.1 This test method covers the laboratory determination of the viscosity of engine oils at 150°C and 1 x 10(6) s(-1) shear rate using a tapered bearing simulator-viscometer (TBS Viscometer) equipped with a refined thermoregulator system. Older TBS units not so equipped must use Test Method D4683-87.

1.2 The Newtonian calibration oils used to establish this test method cover the range from approximately 1.5 to 5.6 cP (mPa•s) at 150°C.

1.3 The non-Newtonian reference oil used to establish this test method has a viscosity of approximately 3.5 cP (mPa•s) at 150°C and a shear rate of 1 x 10(6) s(-1).

1.4 Applicability to petroleum products other than engine oils has not been determined in preparing this test method.

1.5 This test method uses the centipoise (cP) as the unit of viscosity. For information on the equivalent SI unit, the millipascal second (mPa•s) 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 determine the applicability of regulatory limitations prior to use.

2. Referenced Documents
2.1 ASTM Standards:
D4741 Test Method for Measuring Viscosity at High Temperature and High Shear Rate by Tapered-Plug Viscometer
D5481 Test Method for Measuring Apparent Viscosity at High-Temperature and High-Shear Rate by Multicell Capillary Viscometer

3. Terminology
3.1 Definitions:
3.1.1 density - the mass per unit volume. In the SI, the unit of density is the kilogram per cubic metre, but for practical use a submultiple is more convenient. The gram per cubic centimetre is 10(3) kg/m3 and is customarily used.

3.1.2 Newtonian oil or fluid - 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 - an oil or fluid that exhibits a viscosity that varies with changing shear stress or shear rate.

3.1.4 shear rate - the velocity gradient in fluid flow. The SI unit for shear rate is the reciprocal second (s-1).

3.1.5 shear stress - the motivating force per unit area for fluid flow. The area is the area under shear.

3.1.6 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; for practical use, a submultiple, millipascal second, is more convenient. The centipoise is 1 mPa•s and is customarily used.

3.1.6.1 apparent viscosity - the determined viscosity obtained by this test method.

3.1.6.2 kinematic viscosity - the ratio of the viscosity to the density of the liquid. It is a measure of the resistance to 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 centistoke (cSt) is 1 mm2/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 contact position - the rotor height when in rubbing contact with the stator.

3.2.3 idling oil - an oxidatively stable Newtonian oil used to minimize deposits on the rotor/stator operating surfaces when the instrument is held for long periods of time at operating temperatures of 150°C at which other oils may in reasonably short time decompose and leave residues.

3.2.4 non-Newtonian reference oil - a specially selected non-Newtonian reference oil required to establish the proper gap between the rotor and stator to produce an operating shear rate of 1 x 10(6) s(-1).

3.2.5 reciprocal torque intersection, Rti - the rotor position on the micrometer defined by the intersection of two straight lines. These are generated by the reciprocal indicated torque versus rotor height for the non-Newtonian NNR-03 and the Newtonian R-400. The intersection indicates the rotor height at which the rotor/stator cell will generate 1 x 10(6) s(-1) shear rate.

3.2.6 rotor height (rotor position) - the vertical position of the rotor relative to the stator and measured by the platform micrometer.

3.2.6.1 Discussion - For most instruments, a mechanical micrometer is used; the micrometer reading increases as the rotor is lowered and approaches the stator. However, if an electronic micrometer is used, the micrometer reading decreases when the rotor is lowered.

3.2.7 stored position - the rotor position with the rotor 0.50 mm above the contact position.

3.2.8 test oil - any oil for which apparent viscosity is to be determined.