Numerical modelling of hydraulic seals by inverse lubrication theory

Abstract

This article describes a methodology used to achieve a numerical analysis of hydraulic seals by the inverse hydrodynamic lubrication method. The main novelties consist of taking into account the influence of the shear stresses in the lubricant film and in the treatment of hydrodynamic effects on the seal inlet. Each step is detailed and discussed in terms of possible error over the predicted seal performances. It has been shown that the pressure field computed directly from the structure model does not give a realistic approximation of the hydrodynamic pressure in the inlet zone, and a hydrodynamic correction is necessary. Furthermore, it has been shown that if the tangential friction due to the shear stress in the lubricant film is not taken into account, error of about 5 per cent can be made, concerning the predictions of leakage and friction force.

Profile Optimization of Hydraulic, Polymeric, Sliding Seals by Minimizing an Objective Function of Leakage, Friction and Abrasive Wear

“…In Equation (22), as in Nikas [7], the EHD local shear stress (Vη/h − hp /2) is restricted by the limiting shear stress τ L . The latter is the minimum of the shear strength of the EHD film, approximated by τ 0 (1 + αp) with τ 0 being the limiting shear stress of the sealed fluid at atmospheric pressure, and the temperature-dependent shear strength of the sealing ring, τ s = e c τ1 θ+c τ2 (θ in • C; τ s in Pa).…”

“…In most published theoretical studies dealing with the performance of polymeric sliding seals [3], the problem solved involves calculating the film thickness distribution in a sealing contact and from that point on, calculating the leakage rate and the frictional force or the coefficient of friction; some of the most representative numerical studies in this respect are references [7,8,[10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Abrasive wear modeling of seals is not included, except in a handful of studies, given the uncertainty surrounding a wear coefficient such as that included in the well-known Archard wear equation [24][25][26].…”

About the Inverse Theory and the Non-Unicity of the Film Thickness: Novel Approach Generating Equivalent Micro-Grooves and Roughness

“…-The second is the inverse method that is widely used for elastomeric seals. Indeed, according to this theory, the static contact pressure "ps(x)" is assumed equal to the hydrodynamic pressure "p(x)" and the film thickness "h(x)" is computed by using the first and second derivatives of "p(x)" [4,5,6] under non-cavitation conditions.…”

Tribological Behavior of Hydraulic Cylinder Coaxial Sealing Systems Made from PTFE and PTFE Compounds

“…The results of other research concerning the character of friction in the sealing tribological system are described in the works of Kanzaki et al [17], Stupkiewicz et al [18], Fatu et al [19], Crudu et al [20]. It needs pointing out, however, that those works refer only to concrete cases of sealing systems without the possibility of generalization.…”