Geometry Optimization of Textured Three-Dimensional Micro- Thrust Bearings

Abstract

This paper presents an optimization study of the geometry of three-dimensional microthrust bearings in a wide range of convergence ratios. The optimization goal is the maximization of the bearing load carrying capacity. The bearings are modeled as microchannels, consisting of a smooth moving wall (rotor), and a stationary wall (stator) with partial periodic rectangular texturing. The flow field is calculated from the numerical solution of the Navier-Stokes equations for incompressible isothermal flow; processing of the results yields the bearing load capacity and friction coefficient. The geometry of the textured channel is defined parametrically for several width-to-length ratios. Optimal texturing geometries are obtained by utilizing an optimization tool based on genetic algorithms, which is coupled to the CFD code. Here, the design variables define the bearing geometry and convergence ratio. To minimize the computational cost, a multi-objective approach is proposed, consisting in the simultaneous maximization of the load carrying capacity and minimization of the bearing convergence ratio. The optimal solutions, identified based on the concept of Pareto dominance, are equivalent to those of singleobjective optimization problems for different convergence ratio values. The present results demonstrate that the characteristics of the optimal texturing patterns depend strongly on both the convergence ratio and the width-to-length ratio. Further, the optimal load carrying capacity increases at increasing convergence ratio, up to an optimal value, identified by the optimization procedure. Finally, proper surface texturing provides substantial load carrying capacity even for parallel or slightly diverging bearings. Based on the present results, we propose simple formulas for the design of textured micro-thrust bearings.

Tribological Optimization of Thrust Bearings Operated With Lubricants of Spatially Varying Viscosity

“…These irregularities are usually in the form of dimples, mainly rectangular, trapezoidal, cylindrical, or spherical. Recent research efforts, numerical [1][2][3][4][5][6][7][8] and experimental [9][10][11], have demonstrated that properly implemented texture patterns on the stator surface may substantially improve the performance of thrust bearings, in terms of load carrying capacity and friction coeffi cient. As current technology enables the accurate manufacturing of such microscale patterns, contemporary research on the per formance of textured bearings is even more intense, also including optimization of the texture geometry [5][6][7][8].…”

“…Recent research efforts, numerical [1][2][3][4][5][6][7][8] and experimental [9][10][11], have demonstrated that properly implemented texture patterns on the stator surface may substantially improve the performance of thrust bearings, in terms of load carrying capacity and friction coeffi cient. As current technology enables the accurate manufacturing of such microscale patterns, contemporary research on the per formance of textured bearings is even more intense, also including optimization of the texture geometry [5][6][7][8]. Further, recent work has demonstrated that, apart from improving the static frictional characteristics of thrust bearings operating in full-film hydrody namic conditions, artificial surface texturing may also improve (a) the frictional characteristics of thrust bearings operating in mixed lubrication conditions [11] and (b) the dynamic characteristics of thrust bearings (expressed in terms of the stiffness and damping coefficients) [12], Hydrophobic or superhydrophobic surfaces are bio-inspired surfaces, characterized by a combination of micro-and nanoscale roughness [13,14], Superhydrophobic surfaces are resistant to wetting, thus enabling low friction levels in fluid flows.…”

“…Among them, proper implementation of surface treatment technologies, such as artifi cial surface texturing [1][2][3][4][5][6][7][8][9][10][11][12] and surface hydrophobicity [13][14][15][16][17][18][19][20][21][22] have gained substantial attention. The potential and limits of these technologies have not yet been fully investigated.…”

Influence of surface texturing on the hydrodynamic performance of a thrust bearing operating in steady-state and transient lubrication regime

“…The increase of the load-carrying capacity of thrust bearings would allow a reduction of their dimensions, which would be consistent with the current technological trends that require a downsizing of mechanical components. Therefore, the optimization of thrust bearings through surface texturing has been the subject of an increasing number of both theoretical and experimental works [2][3][4][5][6][7][8][9][10].…”

Parameter Optimization of Surface Textures of Oil-lubricated Journal Bearings

“…Papadopoulos et al presented an optimization approach based on genetic algorithms to obtain the optimal texturing patterns to improve the load-carrying capacity of micro-thrust bearings in a wide range of convergence ratios [4]. Zhou et al studied the effects of the texturing parameters on the load carrying capacity and film thickness under different velocities, and obtained the ranges of optimum texturing parameters [5].…”