Features of Transition Modes of Friction Surfaces with Partially Regular Microrelief (original) (raw)
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Influences of the Textured Surface Micro-Texture Depth on the Friction Coefficient
World Journal of Mechanics, 2020
The use of textured surfaces in lubrication to improve the tribological characteristics has been widely studied. The understanding of the textured surface geometric parameters influences on these tribological characteristics could help to improve their applications in industry. In this paper, we purpose to analyze the influence of the micro-texture depth on the friction coefficient experimentally. The experiment is conducted using different copper alloy samples have been the first laser textured with different micro-hole depth (40.83 µm and 46.36 µm). A 3D electronic Olympus microscope is used to visualize the shapes of the holes and find the depths. Then, the friction test has been conducted using these samples with the same velocity. The time variation of the friction coefficient is plotted and analyzed. The analysis of time variation of the friction coefficient shows a reduction of friction coefficient with the increase of the micro-hole depth has been observed. In some cases, this reduction is significant.
Micromachines, 2021
Friction control is a vital technology for reaching sustainable development goals, and surface texturing is one of the most effective and efficient techniques for friction reduction. This study investigated the performance of a micro-dimpled texture under varying texture densities and experimental conditions. Reciprocating sliding tests were performed to evaluate the effects of the micro-dimpled texture on friction reduction under different normal loads and lubrication conditions. The results suggested that a micro-dimpled texture could reduce the coefficient of friction (CoF) under dry and lubricated conditions, and high dimple density results in a lower CoF. The dominant mechanism of the micro-dimpled texture’s effect on friction reduction was discussed, and surface observation and simulation suggested that a micro-dimpled texture could reduce the contact area at the friction interface, thereby reducing CoF.
Tribology Letters, 2012
We present measurements of friction coefficient of lubricated laser surface textured (LST) microstructures with two different geometries. The former is made of a square lattice of microholes; the latter is constituted by a series of microgrooves. We analyze sliding velocities spanning more than two orders of magnitude to cover the entire range from the boundary to the hydrodynamic regime. In all cases, the interfacial pressure is limited to values (relevant to particular manufacturing processes) which allow to neglect macroscopic elastic deformations, piezo-viscosity and oil compressibility effects. The measured Stribeck curves data are compared with those obtained for the flat control surface and show that the regular array of microholes allows to reduce friction over the entire range of lubrication regimes with a decrease of about 50 % in the hydrodynamic regime. On the contrary, the parallel microgrooves lead to an increase of friction compared to the flat control surface with a maximum increase of about 80-100 % in the mixed lubrication regime. These remarkably opposite friction results are then explained with the aid of numerical simulations. Our findings confirm that LST may have cutting edge applications in engineering, not only in classical applications (e.g., to reduce piston-ring friction losses in internal combustion engines) but also, in particular, in technological processes, such as hydroforming, superplastic forming, where the mapping of the frictional properties of the mold has a crucial role in determining the final properties of the mechanical component.
Lubricants, 2016
Surface texturing has been shown to be an effective modification approach for improving tribological performance. This study examined the friction reduction effect generated by square dimples of different sizes and geometries. Dimples were fabricated on the surface of ASP2023 steel plates using femtosecond laser-assisted surface texturing techniques, and reciprocating sliding line contact tests were carried out on a Plint TE77 tribometer using a smooth 52100 bearing steel roller and textured ASP2023 steel plates. The tribological characterization of the friction properties indicated that the textured samples had significantly lowered the friction coefficient in both boundary (15% improvement) and mixed lubrication regimes (13% improvement). Moreover, the high data sampling rate results indicated that the dimples work as lubricant reservoirs in the boundary lubrication regime.
Friction characteristics of microtextured surfaces under mixed and hydrodynamic lubrication
We report experimental and numerical investigations of the friction characteristics of microtextured surfaces. The textures are of size 28–257 mm on stainless steel surfaces, fabricated using micro-casting. Friction characteristics of these surfaces were tested under submerged conditions using a pin-on-disk configuration. Numerical simulations solved the Navier–Stokes equations to predict the texture-induced lift. During hydrodynamic lubricated sliding, the textured surfaces exhibit friction as much as 80% lower than the untextured surfaces. We study the effect of operating conditions on the friction performance of the surfaces for different textures. The trends obtained in the experiments match well with the simulations, and indicate design rules for the implementation of this technology.
Laser Microtextured Surfaces for Friction Reduction: Does the Pattern Matter?
Materials, 2020
Frictional performances of different textures, including axisymmetric and directional patterns, have been tested in the mixed and the hydrodynamic lubrication regimes. Experimental results, corroborated by numerical simulations, show that the leading parameter is the geometrical pattern void ratio since a large number of dimples offers, at low speed, a trap for debris whereas, at high speed, due to the flow expansion in each micro-hole, fosters a fluid pressure drop, the consequent insurgence of micro-cavitation and, ultimately, the reductions of the shear stresses. Furthermore, in this paper, it is shown that, by means of directional textures, equivalent hydrodynamic wedges can be built up, thus establishing different friction performances depending on the flow direction.
Minimize friction of lubricated laser-microtextured-surfaces by tuning microholes depth
Tribology International, 2014
We have investigated the friction properties of lubricated laser micro-textured surfaces. The microtexture consists of a square lattice of micro-holes whose diameter, depth and spacing are controlled during the laser texturing process. All surfaces have the same texture area density, but different diameters and depths of the micro-holes. We measure the coefficient of friction on a range of sliding velocities from the mixed lubrication regime to the hydrodynamic regime. We find that the depth and the diameter of the micro-holes have a huge influence in determining the amount of friction reduction at the interface. Interestingly experiments also show that optimal micro-hole depth values, minimizing the friction in the hydrodynamic regime, are remarkably effective also in the mixed lubrication regime.
Role of Surface Texture on Friction under Boundary Lubricated Conditions
Tribology Online, 2008
Ensuring effective lubrication between sliding surfaces is one of the challenges in the field of tribology. In addition to the conventional parameters like speed, load, contact geometry and material parameters, the surface texture also influences the coefficient of friction. In the present investigation, the effect of surface texture on coefficient of friction under boundary lubricated condition was studied by sliding Al-4Mg alloy pins against EN8 steel discs of various surface textures using pin-on-disc machine. Both isotropic and directional textures were generated on the surfaces of the discs. Scanning Electron Microscopy and optical profilometer studies were carried out on the contact surfaces of both the pins and discs before and after the experiments. The result showed that the coefficient of friction varied considerably with surface textures. In addition, maximum value coefficient of friction was observed when pins slid perpendicular to the unidirectional texture and minimum when pins slid on random texture. Backscattered scanning electron micrographs revealed the transfer of iron from the disc to the pins and it was highest when pins slid perpendicular to the unidirectional texture and least for the random texture. However, no transfer layer of Al-Mg alloy was observed on the steel disc.
Tribological Investigation of Textured Surfaces in Starved Lubrication Conditions
Materials
The present work investigates the friction reduction capability of two types of micro-textures (grooves and dimples) created on steel surfaces using a vertical milling machine. The wear studies were conducted using a pin-on-disc tribometer, with the results indicating a better friction reduction capacity in the case of the dimple texture as compared to the grooved texture. The microscopic images of the pin surface revealed deep furrows and significant damage on the pin surfaces of the groove-textured disc. An optimization of the textured surfaces was performed using an artificial neural network (ANN) model, predicting the influence of the surface texture as a function of the load, depth of cut and distance between the micro-textures.
Effect of Surface Texture on the Sliding Pair Lubrication Efficiency
Lubricants
The paper presents certain problems related to the lubrication of textured surfaces. It was noted that for a specific load, the lubrication effectiveness will depend on the shape, size and mutual distribution of the texture’s elements. Proposals for determining the lubrication irregularity parameters were presented for textures with a rectangular mesh and round recesses. The experimental part presents the laser texturing methodology, tribological testing methodology and preliminary test results where the significant role of the relationship between the trajectory of motion and the texture mesh was demonstrated.