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1

Ridge geometry effect on the behavior of elastohydrodynamic lubrication of point contact problem

Al-Samieh Mohamed F. Abd

Archive of Mechanical Engineering

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2020

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LXVII, nr 4

491--508

EN

A numerical solution is presented to investigate the influence of the geometry and the amplitude of the transverse ridge on the characteristics of elastohydrodynamic lubrication for point contact problem under steady state condition. Several shapes of ridges with different amplitudes are used in the stationary case, such as flat-top ridge, cosine wave ridge and sharp ridge of triangular shape. Results of film thickness and pressure distributions of the aforementioned ridge feature are presented at different locations through an elastohydrodynamically lubricated contact zone for different amplitude of the ridge. Simulations were performed using the Newton-Raphson iteration technique to solve the Reynolds equation. The numerical results reveal that, to predict optimum solution for lubricated contact problem with artificial surface roughness, the geometrical characteristics of the ridge should have profiles with smooth transitions such as those of a cosine wave shape with relatively low amplitude to reduce pressure spike and therefore cause the reduction in the film thickness. The position of the location of the ridge across the contact zone and the amplitude of the ridge play an important role in the formation of lubricant film thickness and therefore determine the pressure distribution through the contact zone.

2

Couette flows of fluids with pressure dependent viscosity

Rajagopal K. R.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 3

573-585

EN

For liquids such as water, for a range of pressures for which the density remains nearly constant, the viscosity could change by several orders of magnitude. Thus, such liquids could be approximated as incompressible liquids whose viscosity depends on the pressure. Stokes (1945) recognized this possibility and the fact that the viscosity could be considered to be independent of the pressure in only special flows. That this is indeed so has been verified in the case of numerous liquids (Bridgman, 1931). In this short study, we allow the viscosity of the fluid to be dependent on the pressure and investigate the consequence of the effect of gravity in simple flows such as Couette flows between parallel plates. We find that gravity can have a profound effect on the structure of the flow. Its presence leads to the concentration of vorticity adjacent to one of the plates.

3

On the micro-tribology of elastomeric contacts

Moore D. F.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 3

903-910

EN

An overview of micro-tribological events, including micro-adhesion, micro-hysteresis and micro-lubrication is presented in this paper. The link between micro-lubrication and elastohydrodynamics is inseparable, but it appears that elastomer properties have diminishing importance as the scale of texture reduces. In the limit, micro-hysteresis effects give way to micro-adhesion, the latter depending critically on the harshness of micro-texture. Lubricant entrainment over asperity peaks is a function primarily of macro-texture, in particular the slope of such asperities and the void volume created by the macro-texture. This void volume acts as minute lubricant reservoirs which supply the entrainment mechanism and ultimately oppose the adhesion-generating harshness effect. There has been a limited investigation as reported in the literature of the macro-tribology of elastomeric contacts, but very little in the case of micro-events. This is surprising in view of the crucial relevance of such phenomena to an understanding of sliding seals, rubber mounts and tyre friction.