Paper VI(ii) On the flow perturbations and friction reduction introduced by surface dimples

Proceedings of the Institution of Mechanical Engineers, Part J:

Pascovici

et al. 2010

180

147

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 cavitation 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 evaluated 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.

Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Optimizing surface texture for hydrodynamic lubricated contacts using a mass-conserving numerical approach

Dobrica¹,

Proceedings of the Institution of Mechanical Engineers, Part J:

Pascovici

et al. 2010

180

147

“…All of them reveal a substantial reduction in friction torque and an improvement in load-carrying capacity. 1,[5][6][7][8] Conversely, some studies show that surface texturing is only effective for cases of starved or parched lubrication. For fully flooded lubrication, the effect of surface texturing is diminished and, in terms of power losses, is actually detrimental.…”

Section: Introductionmentioning

confidence: 99%

An experimental analysis of the hydrodynamic contribution of textured thrust bearings during steady-state operation: A comparison with the untextured parallel surface configuration

Henry

Bouyer

Proceedings of the Institution of Mechanical Engineers, Part J:

2014

Textured surfaces are the subject of a great deal of research work in tribology, which mainly involves numerical studies of lubricated contacts. A variety of shapes and arrangements of textures can be found, these being as numerous as the different authors. Depending on the configuration, it has been shown that the presence of the texture can provide better lubrication efficiency through both a reduction of friction and an increase in load-carrying capacity. However, improving bearing performance implies a specific geometrical configuration for given operating conditions. The improvement in lubricated contact performance by texturing the active surface has been demonstrated using experimental studies concerning, for example, pin-on-disk, mechanical seal, camshaft, journal bearing, thrust bearing, and piston ring set-ups. The objective of the present experimental analysis is to provide, using local measurements, a better understanding of the influence of surface texturing on the steady-state behavior of thrust bearings. To achieve this goal, the experimental device is equipped with 80 sensors such as thermocouples and pressure transducers which allowed a proper assessment of the phenomenology at the film/pad interface. The tests are conducted on five hydrodynamic thrust bearings, among which four are textured. Results show that, for the studied configurations, the textured thrust bearings can help to reduce friction up to 30% at low loads while for heavy loads, their performance is equivalent or even lower than that of an untextured planar bearing.

“…Texturing one of the surfaces of a lubricated contact has been shown to have beneficial effects experimentally, leading to increased hydrodynamic lift and lower friction coefficients [1]. Such effects were revealed in mechanical seals [2,3], parallel sliders [4], and reciprocating (cylinder-liner) contacts [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Such effects were revealed in mechanical seals [2,3], parallel sliders [4], and reciprocating (cylinder-liner) contacts [5,6]. Since the positive texture effects were experimentally verified [1][2][3][4][5][6], the interest in numerical models able to predict and explain these effects has increased rapidly.…”

Section: Introductionmentioning

confidence: 99%

About the validity of Reynolds equation and inertia effects in textured sliders of infinite width

Dobrica

Proceedings of the Institution of Mechanical Engineers, Part J:

2009

173

129

Numerous recent studies focus on modelling the lubricant flow in macro-textured configurations, using the Navier-Stokes, Stokes, and Reynolds equations. Several of these studies show that important, lift generating inertia effects are present in textured configurations, and conclude that Reynolds assumptions do not hold true for such contacts. A similar analysis is performed in this paper, for parallel sliders of infinite width, but with quite different conclusions. Two main observations are made based on the results presented herein: (a) inertia effects cannot be analysed by single texture cell models -for example, in the case of partial inlet texturing, inertia shows a clear negative influence, contradicting the previously reported lift generating effects; (b) the validity of Reynolds equation in textured sliders cannot be decided by the Reynolds number (Re) alone, and the texture aspect ratio (λ) has an equally important influence on Reynolds equation validity. Finally, charts presenting the relative difference between Reynolds and Navier-Stokes solutions in terms of λ and Re are discussed.