SPECIAL ISSUE PAPER 737 Optimizing surface texture for hydrodynamic lubricated contacts using a mass-conserving numerical approach M B Dobrica 1∗ , M Fillon 2 , M D Pascovici 3 , and T Cicone 3 1 Department of Engineering, Tecnitas, Levallois-Perret, France 2 Département Génie Mécanique et Systèmes Complexes, Institut Pprime, Université de Poitiers, ENSMA, Futuroscope, France 3 Department of Machine Elements and Tribology, Politehnica University of Bucharest, Romania The manuscript was received on 11 May 2009 and was accepted after revision for publication on 16 April 2010. DOI: 10.1243/13506501JET673 Abstract: Surface texturing has been shown to reduce friction and increase the film thickness in various tribological applications (hydrodynamic bearings, mechanical seals, and cylinder–liner contacts). However, only few studies discuss optimal texturing properties, and most of them focus on the optimal dimple shape. This article proposes an in-depth study on the influence of cavita- tion and of different texturing parameters, especially the dimple depth, the texture extent, and the dimple aspect, on the hydrodynamic performance of textured contacts. The results are derived numerically, for contacts between plane surfaces that are parallel or inclined with respect to each other. The performance gains (film thickness and friction force) obtained by texturing are evalu- ated with respect to the performance of smooth contacts. Most notable findings are the optimal extent of the textured region (partial texturing and trapezoidal shape) and the optimal dimple aspect (longitudinal). Cavitation is shown to have a significant influence on the performance of near-parallel textured contacts, although it does not appear to contribute to the generated hydrodynamic lift. It is equally shown that the dimple arrangement with respect to the leading edge is a determining factor for the performance of near-parallel textured sliders. Keywords: hydrodynamic lubrication, surface texture, cavitation, optimization 1 INTRODUCTION Surface texture has been shown experimentally and theoretically to have beneficial effects over the hydro- dynamic characteristics of mechanical seals (in par- allel sliding) as early as 1966 [1–3], as it was recently reported by Etsion [4]. Two decades later, in 1987, the experimental works of Rightmire et al.[5] have shown that surface texture can also reduce friction in tilting- pad hydrodynamic thrust bearings. Another decade later, Etsion and his co-authors took a closer look to the possible amelioration of the performance of vari- ous lubricated contacts by means of surface texturing. Starting with mechanical face seals [6, 7], followed by reciprocating contacts [8, 9] and parallel thrust bearings [10, 11], it was shown that surface texture ∗ Corresponding author: Department of Engineering, Tecnitas, 66, rue de Villiers, Levallois-Perret 92532, France. email: mihai.dobrica@tecnitas.com is indeed improving the hydrodynamic behaviour of these parallel contacts. In non-cavitated hydrodynamic contacts where Reynolds assumptions hold true, it can be theoretically shown that full texturing has a negative impact on both hydrodynamic lift and viscous friction [12, 13]. In order to explain the positive texture effects observed in fully textured parallel sliders, two theories were put forward. The first one considers the cavitation phenomena as the source of these positive effects. Accordingly, the presence of dimples creates an alter- nation of converging and diverging film regions, in which the pressure varies between a positive value in the lubricated regions and the vaporization pres- sure in the cavitated regions. Consequently, an overall positive resultant is obtained [10]. A second theory postulates that the load capacity generated in fully textured parallel sliders is caused by inertia effects, also called ‘convective inertia’ [14]. It was recently shown that this theory is inaccurate and that iner- tia effects have, in general, a negative influence over JET673 Proc. IMechE Vol. 224 Part J: J. Engineering Tribology