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Rheological study of solidified lubricant oils under very high pressure by observing microsphere deformation and viscosity prediction
Author(s) -
Nakamura Yuichi,
Takimoto Akira,
Matsui Masahito
Publication year - 2010
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.110
Subject(s) - lubricant , rheology , materials science , shear stress , composite material , hydrostatic pressure , shear (geology) , viscosity , traction (geology) , deformation (meteorology) , shear rate , hydrostatic stress , thermodynamics , geology , physics , geomorphology , finite element method
The rheological properties of solidified lubricant oils under pressure were evaluated by observing large plastic deformation of metal microspheres, occurring due to non‐hydrostatic pressurisation in the oils when using a diamond‐anvil cell pressure‐generating apparatus. Defining the solidification pressure as the onset pressure of plastic deformation of aluminum sphere obtained solidification pressures for traction oils were about 0.5 GPa, whereas those for mineral and synthetic oils ranged from 1.2 to 2 GPa. By substituting the solidification pressures and pressure–viscosity coefficients in the Barus equation, viscosities at the solidification pressure were obtained. The values were different for each oil and were within the order of 10 6 –10 8 Pas. Based on several assumptions, shear stresses of the solidified oils could be estimated up to 5 GPa from the deformed Cu spheres. The shear stresses for a traction oil were almost equal to the mean shear stress obtained from a traction test between 1.0 and 1.7 GPa. Copyright © 2010 John Wiley & Sons, Ltd.