This paper deals with modeling the non-linear rheological behavior of lubricating greases at very low shear rates. With this aim, dynamic linear viscoelastic, non-linear stress relaxation, transient and steady-state shear flow, and transient first normal stress difference measurements have been carried out on a diurea-derivative lubricating grease. A factorable non-linear viscoelasticity model, the Wagner integral model, derived from the K-BKZ constitutive equation, was used in order to predict the non-linear rheological response of the above-mentioned lubricating grease under shear. The time-dependent part of the model was described by its linear relaxation spectrum, whilst two different damping functions (Wagner and Soskey-Winter’s damping functions) were analysed as the strain-dependent factor. The continuous linear relaxation spectrum was estimated, using regularization techniques, from the dynamic linear viscoelasticity functions. The damping function was calculated from non-linear stress relaxation tests. The constitutive model, with Soskey-Winter’s damping function, predicted the steady-state flow curve, the transient shear stress and the transient first normal stress differences of the lubricating grease studied fairly well. [S0742-4787(00)01603-9]
Modeling of the Non-Linear Rheological Behavior of a Lubricating Grease at Low-Shear Rates
Contributed by the Tribology Division for publication in the ASME JOURNAL OF TRIBOLOGY. Manuscript received by the Tribology Division June 8, 1999; revised manuscript received December 29, 1999. Associate Technical Editor: B. O. Jacobson.
Madiedo , J. M., Franco , J. M., Valencia , C., and Gallegos, C. (December 29, 1999). "Modeling of the Non-Linear Rheological Behavior of a Lubricating Grease at Low-Shear Rates ." ASME. J. Tribol. July 2000; 122(3): 590–596. https://doi.org/10.1115/1.555406
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