Influence Of Surface Texture Research Articles

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

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.

Role of surface textures on tribological behaviour of HSS

Surface contact area is one of the most influential factors for increase in friction that leads to wear. Reducing surface contact area by producing textures on the surface leads to a drastic reduction in wear rate. This method is very effective in high speed steel which is used for machining in dry conditions while its effectiveness can be further increased by the application of lubricants. This research paper presents the investigation on wear behaviour of HSS using pin-on-disc dry sliding wear test method under different textured conditions. The tribological parameters like wear rate, wear resistance, material loss and co-efficient of friction were evaluated for textured and non-textured conditions. Micro dimple areal texture and micro linear grinding texture were produced on the HSS surface and the results obtained were compared with non-textured HSS surface to study the influence of surface texture on tribological properties.

Bionic Design of Koch Snowflake Surface Texture and Its Effects on Air Frictional Noise of High Speed Train

In order to reduce the air frictional noise at the air-carriage interface of high speed train, a Koch type snowflake surface structure is designed to simulate the fractal structure of snowflake and analyzed with the theory of computational fluid dynamics(CFD) and the method of bionic design for the surface of high speed train. The compressible N-S equation is solved using unstructured hybrid grid and k ?? model and the noise distribution is solved based on broadband noise source. Simulation results demonstrate that the air frictional noise is greatly reduced because of the secondary vortex generated in the Koch snowflake like surface structure. A kind of multi scale surface structure consists of Koch snowflake cells on two scales and a sort of compound surface texture combining cells of Koch snowflake and circular dents are designed in order to further explore the influence of surface texture on the decrease of the noise of high speed train; that multi scale surface texture is better than single texture but compound surface texture is worse than the better one of the single texture in reduction of the air frictional noise, which provide an effective guidance for the study of reducing the air frictional noise of high speed train.

Photometric properties of Mars soils analogs

We have measured the bidirectional reflectance of analogs of dry, wet, and frozen Martian soils over a wide range of phase angles in the visible spectral range. All samples were produced from two geologic samples: the standard JSC Mars‐1 soil simulant and Hawaiian basaltic sand. In a first step, experiments were conducted with the dry samples to investigate the effects of surface texture. Comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures. In a second step, water was introduced to produce wet and frozen samples and their photometry investigated. Optical microscope images of the samples provided information about their microtexture. Liquid water, even in relatively low amount, resulted in the disappearance of the backscattering peak and the appearance of a forward‐scattering peak whose intensity increases with the amount of water. Specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample. Icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice. We discuss the implications of these measurements in terms of the expected photometric behavior of the Martian surface, from equatorial to circum‐polar regions. In particular, we propose some simple photometric criteria to improve the identification of wet and/or icy soils from multiple observations under different geometries.

Parasitic absorption in the rear reflector of a silicon solar cell: Simulation and measurement of the sub-bandgap reflectance for common dielectric/metal reflectors

The rear side of a silicon solar cell is often designed to minimize surface recombination, series resistance, and cost, but not necessarily parasitic absorption. We present a comprehensive study of parasitic absorption in the metal layer of solar cells with dielectric/metal rear reflectors. The sub-bandgap reflectance of a solar cell or test structure is proposed as an experimentally accessible probe of parasitic absorption, and it is correlated with short-circuit current density. The influence of surface texture, dielectric refractive index and thickness, and metal refractive index on sub-bandgap reflectance-and thus current is then both calculated and measured. From the results, we formulate design rules that promote optimum infrared response in a wide variety of silicon solar cells. (C) 2013 Elsevier B.V. All rights reserved.

Influence of surface texture on tribological performance of AlCrN nanocomposite coated titanium alloy surfaces

The modification of surface layer of machine elements used for engineering applications requires modern tools and techniques for improving its functional aspect and enhanced life. In this study, modification of surface layer was done by combining laser texturing and filling the textured surface by hard wear-resistant coating. This study aimed at investigating the friction and wear behavior of nano aluminum chromium nitride (AlCrN) composite coating over modified titanium alloy (Ti6Al4V) surfaces under dry sliding contact condition. The surface of as-received titanium alloy substrate was lapped and laser surface texturing was performed on the lapped surface. Magnetron-sputtered physical vapor deposition technique was preferred for coating. Scanning electron microscope, energy dispersive X-ray and microhardness tests were performed to characterize the coating. Further, to evaluate the bonding strength of coating against modified surfaces, scratch tests were performed by a scratch tester. Using pin-on-disc tribometer, the coated samples were subjected to tribological investigation for dry sliding contact conditions. The effect of normal load on friction and wear characteristics were examined and discussed. The performance of these coatings on textured and lapped surfaces was compared. Critical parameters such as variation in coefficient of friction and specific wear rate were reported. The influence of textured surface on coating performance was discussed.

Influence of surface texturing and hard chromium coating on the wear of steels used in cold rolling mill rolls

The present work analyzed the wear behavior of surface modifications often used in cold rolling mill rolls. Different surface modifications were carried out on samples produced from a fragment of a rolling mill roll: i) shot blasting texturing using steel spheres (T); ii) chromium plating (C); iii) shot blasting texturing with subsequent hard chrome plating (TC); iv) and hard chrome plating with subsequent shot blasting texturing (CT). Before the surface modifications the samples were heat treated and ground on both faces. Sliding wear tests were performed using a reciprocating movement of a ball over flat configuration under a load of 9.8N. Abrasive wear tests used a free ball microabrasion tester with SiO2 abrasive particles. Surface texturing increased Sq, Sdq and Spk and reduced Sbi of the uncoated samples, i.e., the surface became rougher, whereas hard chrome coating after texturing did not alter much the surface topography, although a slight decrease of Spk and a slight increase of Sbi of the samples were detected i.e., a slight smoothening of the textured surfaces occurred due to chromium plating. The results of the reciprocating tests showed, after running in, average friction coefficients of 0.38±0.01 for all the samples tested, evidencing no significant change in the coefficient of friction as a function of surface modification. Surface texturing increased the sliding wear of the counterbodies when compared with that obtained by the sample without modification (WM) by 70% for 1h tests and by 35% for 10h tests. When the surface was textured before chromium plating, the wear rate of the counterbody did not increase in relation to the C sample for the 1h test, but was the highest for 10h tests, with an increase of 200% in relation to the C sample. On the other hand, chromium plating increased the wear rate of the specimens, for conditions either with or without previous texturing. The addition of the hard chromium coating promoted the formation of a tribolayer on the counterbody consisting of chromium and oxygen. For the samples without hard chrome coating, the tribolayer consisted of iron and oxygen and it was located on the specimen surface. The results of microabrasion showed that, for the uncoated samples, surface texturing increased abrasion resistance (24%). The reduction was higher (67%) for the coated samples, but previous texturing of the coated samples increased abrasion (54%) when compared with the coated samples.

S112033 火砕流堆積物を用いた歯面仕上げ法の開発に関する基礎研究 : 浸炭焼入れ鋼の面圧強さに及ぼす表面性状の影響([S112-03]伝動装置の基礎と応用(3))

In order to prevent environmental pollution in the manufacturing process and to obtain high load-carrying capacity of the power transmission gears, the tooth surface-finishing methods using volcanic-ashes were investigated. First, case-carburized test rollers were finished by cylindrical grinding machine. Secondly, the ground surfaces were finished by using volcanic-ashes. Third, the influence of surface texture on surface durability of test rollers was examined using a 2-roller-type fatigue testing machine. For test rollers with finished surface, the following results are obtained under the heavy load conditions: The surface temperature occurred by friction is low. During running, the amount of wear and the number of pits decrease. From these considerations, it is found that the surface finished by use of volcanic-ashes containing various chemical compositions is smoother than ground surface. Furthermore, in the case of the alloy steel of the same quality and same process of case-carburizing, surface durability of case-carburized gears is improved by using volcanic-ashes.

Molecular dynamics simulation of lubricated contact between textured surfaces

AbstractIn this contribution, the friction at atomical scale has been investigated by using molecular dynamics (MD) simulations. This work surves as a preliminary study on the influence of surface texture on the friction at atomic scale, where simple rectangular grooves are added to the contact surface. Our results suggest definite dependence of the friction on the orientation of the grooves, which decreases as the velocity increases. For a given velocity, an optimal direction of sliding which gives the minimum averaged friction coefficient can be identified. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analysis of Strain Rates and Microstructural Evaluation during Metal Forming: Role of Surface Texture and Friction

The surface texture of a die plays an important role in friction during metal forming. In the present study, unidirectional and random surface finishes were produced on hardened steel plate surfaces. To understand the influence of surface texture on friction, experiments were conducted using Al-Mg alloy pins that slid against steel plates of different surface textures. In the sliding experiments, a high coefficient of friction was observed when the pins slid perpendicular to the unidirectional grinding marks and low friction occurred when the pins slid on the random surfaces. Finite element simulations were performed using the measured friction values to understand the stress and strain evolutions in the deforming material using dies with various friction. The numerical results showed that the states of stress and strain rates are strongly influenced by the friction at the interface and hence would influence the final material microstructure. To substantiate the numerical results, laboratory compression tests were conducted. Different surface textures were obtained in order to experience different friction values at different locations. A large variation in the microstructure at these locations was observed during experiments, verifying that surface texture and die friction significantly influence fundamental material formation behavior.

Water Vapor Emission From Rigid Mesoporous Materials during the Constant Drying Rate Period

It has long been thought that the evaporation rate from mesoporous materials during the constant drying rate period (CDRP) is equal to that of a free-water surface, due to the presence of a liquid film covering the surface of the material. In this article we review several early articles and demonstrate that the experimental scrutiny this hypothesis has received is insufficient. Further, we report a set of evaporative drying experiments on eight building materials whose results also do not confirm such hypothesis. Indeed, the drying rate during the CDRP is not equal either among the tested materials or between these and the free-water surfaces. To explain the differences in drying rate, we have looked at the influence of surface texture and porosity. We have concluded that surface texture, which could increase the effective surface area of the materials, did not have a relevant effect on the CDRP drying rate. However, we have found a good correlation between the CDRP drying rate and capillary porosity. This is consistent with the hypothesis that drying occurs at the pore level during the CDRP. Further, it contradicts the suggestion that there is a film of water covering the surface of the materials during this period.

The lubricant retaining effect of micro-dimples on the sliding surface of PDMS

The frictional behavior of elastomers is characterized by compliance of asperities, special surface chemistry, and wetting properties. The objective of this paper is to investigate the coupled influence of surface texture and wettability on the lubrication of an elastomer contact. Patterns of micro-dimples were fabricated on disks of a polymer material, PDMS. An oxygen plasma treatment was used to hydrophilize the disk surfaces. Friction tests of the disks sliding against a spherical pin of PDMS were carried out. The experimental results indicate that the effect of surface texture is different for PDMS with different wetting properties.

Influence of surface texture on the defect‐induced breakdown behavior of multicrystalline silicon solar cells

ABSTRACTThe defect‐induced diode breakdown behavior in multicrystalline silicon solar cells, which is located at recombination active crystal defects, is influenced by the surface texturization because the wet chemical treatment selectively etches grain boundaries and dislocations, resulting in etch pits. On textured surfaces, the defect‐induced breakdown voltage is decreased, and the slope of the local reverse I–V characteristics in breakdown is steeper. We find that the local defect‐induced breakdown voltage correlates with the depth of the etch pits. It is suggested that the enhanced electric field in the space charge region at the tip could be superimposed by an electric field around metallic precipitates because of the internal Schottky contact formation with the surrounding silicon. The combined electric field could be responsible for the dependence of the defect‐induced breakdown behavior on the surface texture. Copyright © 2012 John Wiley & Sons, Ltd.

Influence of Surface Texture on Lubrication Performance of Hydrodynamic Journal Bearing

A finite-difference numerical model is used to study the influence of surface texture on lubrication performance of hydrodynamic journal bearing. Reynolds equation is adopted to calculate the bearing load carrying capacity, friction force and friction coefficient under different width-diameter ratio, different eccentricity ratio and different texture location. Results show that partial texture along the circumferential direction on the bearing with small width-diameter ratio will increase bearing performance appreciably. Partial texture along the axial direction will decrease friction coefficient effectively, especially at the film inlet zone or the position of film pressure trending to zero.

Surface-Induced Self-Assembly of Dipeptides onto Nanotextured Surfaces

There is an increasing interest for the utilization of biomolecules for fabricating novel nanostructures due to their ability for specific molecular recognition, biocompatibility, and ease of availability. Among these molecules, diphenylalanine (Phe-Phe) dipeptide is considered as one of the simplest molecules that can generate a family of self-assembly based nanostructures. The properties of the substrate surface, on which the self-assembly process of these peptides occurs, play a critical role. Herein, we demonstrated the influence of surface texture and functionality on the self-assembly of Phe-Phe dipeptides using smooth silicon surfaces, anodized aluminum oxide (AAO) membranes, and poly(chloro-p-xylylene) (PPX) films having columnar and helical morphologies. We found that helical PPX films, AAO, and silicon surfaces induce similar self-assembly processes and the surface hydrophobicity has a direct influence for the final dipeptide structure whether being in an aggregated tubular form or creating a thin film that covers the substrate surface. Moreover, the dye staining data indicates that the surface charge properties and hence the mechanism of the self-assembly process are different for tubular structures as opposed to the peptidic film. We believe that our results may contribute to the control of surface-induced self-assembly of peptide molecules and this control can potentially allow the fabrication of novel peptide based materials with desired morphologies and unique functionalities for different technological applications.

Influence of Surface Texturing on the Electrical and Optical Properties of Aluminum Doped Zinc Oxide Thin Films

An aluminum doped zinc oxide (AZO) film for front contacts of thin film solar cells, in this work, were deposited by r.f. magnetron sputtering, and then etched in diluted hydrochloric acid solution for different times. Effects of surface texturing on the electro-optical properties of AZO films were investigated. Also, to clarify the light trapping of textured AZO film, amorphous silicon thin film solar cells were fabricated on the textured AZO/glass substrate and the performance of solar cells were studied. After texturing, the spectral haze at the visible range of 400 ~750 nm increased substantially with the etching time, without a change in the resistivity. The conversion efficiency of amorphous Si solar cells with textured AZO film as a front electrode was improved by the increase of short-circuit current density (<TEX>$J_{sc}$</TEX>), compared to cell with flat AZO films.

Numerical investigation on the influence of surface texture on the performance of hydrodynamic journal bearing

Many researchers have adopted various techniques for improving the performance characteristics of journal bearing. Apart from other parameters, incorporation of different forms of surface texture (sinusoidal, dimple, spherical etc.) on bearing or shaft also helps to increase the load carrying capacity and reduce the friction coefficient etc. in the journal bearing. Present study investigates the influence of different forms of surface texture on finite journal bearing which has been considered in the form of negative texture (micro cavities) at different locations of bearing surface. The Governing equations are solved numerically through finite difference approach for analysis of texture effects on bearing characteristics. It has been observed that the presence of micro cavities at different locations of bearing surface help in enhancing the bearing performance. It has also been found that the negative half wave texture enhances the bearing performance more in comparison to full wave texture on bearing surface.

An optimum design model for textured surface with elliptical-shape dimples under hydrodynamic lubrication

The influence of surface texture in the form of the elliptical-shape dimples with various depths, diameters, area ratios and different operation parameters on friction coefficient has been investigated under conditions of hydrodynamic lubrication. The results show that, the larger the optimum diameter, the larger the corresponding optimum depth becomes; the optimum area ratio is not bound up with the texture parameters and operating parameters; the optimum depth increased while the optimum diameter decreased as the velocity became larger and the load became smaller. A model for the optimum design of textured surface was built and then validated by the experiments.

9I-16 表面テクスチャリングを施した人工関節表面がトライボロジー特性に与える影響(GS-3 医療システムとデバイス)

9I-16 表面テクスチャリングを施した人工関節表面がトライボロジー特性に与える影響(GS-3 医療システムとデバイス)

The Influence of Surface Texture on Rolling-Contact Fatigue of PEEK Bearings in Water

The effect of machining conditions on the rolling contact fatigue (RCF) strength of PEEK polymer bearings was investigated. RCF tests were carried out by using bearings machined by different conditions. The surface profile and roughness were observed before and after testing by laser confocal microscope. Pitting and cracking were associated with the different initial surface conditions. From the obtained results, we found that the RCF strength of machined surfaces decreases when the surface becomes rougher.