Work Item
ASTM WK85429
New Test Method for The Determination of Rheological Properties of Lubricating Greases
1. Scope
covers the determination the storage modulus and flow point stress for greases with NLGI grades from 1 to 3. Although the test method may be conducted on greases softer than NLGI 1 (e.g. NLGI 0 and 00), results on these softer greases are outside the scope of the precision statement. The storage modulus is a measure of the solid-like behavior of a grease. The point at which the storage modulus and the viscous or loss modulus are equal may also be determined and this may be used as a value for the flow point stress of the sample.
Keywords
18.1 consistency; elastic modulus; flow point stress; grease; G' ; G'' loss modulus; oscillation; oscillatory amplitude sweep; storage modulus; viscous modulus
Rationale
Ballot Rationale: The industry requires a method which will allow the assessment of the rheological properties of lubricating grease. This method, which utilizes a controlled stress rheometer requires a small amount of material which makes it useful for analysis of in-use samples or those for which only small amounts are available. The value for the storage modulus (G') obtained from this method is an indication of the consistency or hardness of a sample. Another value obtained from the method is the flow point stress. The flow point stress is the oscillation stress in Pascals where the storage modulus and viscous modulus (G'') are the same. This G'/G'' cross-over point is an indication of the stress needed to cause the sample to flow.
Previously this method had been balloted and the statistics developed for G’ and flow point stress values. These are now grouped by NLGI Grade to make the data more user friendly The text has also been revised to reflect negatives and comments received.
The title and scope are in draft form and are under development within this ASTM Committee.
Work Item Status
Date Initiated: 02-27-2023
Technical Contact: Gareth Fish
Item: 000
Ballot:
Status: