Yield Behavior of ASTM Mobility Test Greases

This technical report presents the findings of a study evaluating the yield behavior of three test greases from different vendors using an ASTM round robin test. The objective was to assess grease mobility under pressure in a defined capillary, similar to a creep test conducted by controlled stress rheometers. The report details the methods employed, including the use of a controlled stress rotational rheometer and modulated differential scanning calorimetry (MDSC) to analyze the greases at various temperatures. The study outlines the rheometry testing procedures, including the evaluation of viscosity and yield stress under different stress conditions. Results indicate variations in the yield points of the greases at different temperatures, with specific rankings established based on viscosity measurements. The report provides graphs illustrating viscosity versus stress relationships, highlighting the complexities in deriving accurate viscosity data at lower temperatures. Overall, the findings contribute to understanding the performance characteristics of greases in mobility tests.