Aqueous dispersions of gelled collagen particles. Part 2: numerical technique for tribological properties

Abstract

Purpose

To propose a new numerical elastohydrodynamic (EHD) analysis method suited to cinematic pairs lubricated with aqueous dispersions of collagen gelled media.

Design/methodology/approach

In comparison with traditional lubricants, these media are characterized by an apparent viscosity that increases with film thickness. Hence, the Reynolds equation has been numerically solved taking into account the new rheological law. The apparent viscosity of 4 percent collagen gel dispersions, as measured at a fixed shear rate of 100 l/s, is in the range 2‐5 Pa s, when film thickness varies between 20 and 200 μm. These experimental data have been fitted using a power law. The proposed analysis method has been applied to a 180° partial bearing, which rigid journal rotates in a flexible sleeve, made up by a resin shell.

Findings

The results of this tribological analysis have been compared with those concerning traditional isoviscous fluids which viscosity has been set equal to the viscosity of the gelled media when the film thickness is constant, i.e. in the unloaded bearing. The minimum film thickness calculated has been turned out equal to 66.8 μm in the former case, and 27.6 μm in the latter case. Furthermore, when the cinematic pair is lubricated with the aqueous gel media, film thickness distribution over the bearing surface is more uniform, active film region is wider and, consequently, peak pressure is lower than when the isoviscous lubricant is employed.

Research limitations/implications

For lightly loaded journal bearings, the dependence between apparent viscosity and the shear rate in the lubricant film has been neglected, so that the apparent viscosity has been considered changing only with the film thickness.

Originality/value

The paper introduces a new numerical EHD analysis method for use with cinematic pairs lubricated with aqueous dispersions of collagen gelled media.

Citation

Stefani, F., Ferrari, A. and Beruto, D.T. (2006), "Aqueous dispersions of gelled collagen particles. Part 2: numerical technique for tribological properties", Industrial Lubrication and Tribology, Vol. 58 No. 5, pp. 247-253. https://doi.org/10.1108/00368790610682644