Surface Microtexture Research Articles

A Study on the Cavitation Effect of Elastic Material with Textured Surfaces under Fluid Lubrication Conditions

This study investigates the effect of the elastic surface micro-texture on the cavitation and lubrication characteristics of the friction pairs through theoretical and experimental research. Through numerical simulations and experiments, the influences of the elastic modulus and sliding speed on the lubrication performance of the friction pair are studied. The results show that under certain speed and load conditions, the friction coefficient of the elastic texture is smaller, and the lubrication performance is better than that of the rigid texture. Increasing the sliding speed and texture spacing properly can improve the lubrication performance of elastic friction pairs. In addition, as the elastic modulus decreases, the elastic deformation and oil film thickness increase, and the cavitation phenomenon becomes more significant. Thus, the lubrication performance of the friction pair is improved.

Machining performance of micro-pit and micro-groove composite textured tools in tungsten alloy turning

Tungsten alloys are widely used in aerospace because of their high-temperature resistance, corrosion resistance, high strength, and other excellent comprehensive properties. But tungsten alloys are typical hard-to-machining materials. Surface micro-textures can improve friction properties, such as preparing micro-textures on the surface of cutting tools for tungsten alloys, which is expected to enhance the cutting performance of tungsten alloys. Still, the relevant cutting laws need to be further studied. A combination texture of micro-pit and micro-groove was designed, and the micro-textured tool surface was prepared by laser machining. Compared with non-textured tools, micro-pit and micro-groove composite textured tools can effectively improve the processing quality of tungsten alloys. It happened because textures on the tool’s surfaces enhance machining performance by reducing the actual contact area between the tool and the chip and storing lubrication medium. At the same time, comparative experiments of micro-textured tools and non-textured tools were carried out. The results showed that when cutting W93NiFe alloys with textured and non-textured tools, the maximum reduction in resultant cutting forces with textured tools was 9%. The maximum reduction in surface roughness was 39.3%, the surface burr height of the tungsten alloy workpiece was lower, the number of surface grooves was lesser, and the surface was more flat. The research results are significant in achieving the efficient processing and high-quality manufacturing of tungsten alloys.

Effect of Micro-Texture on Cutting Performance of PCBN Cutter

The research aimed to delve into the intricate relationship between surface microtexture and the cutting performance of a PCBN cutter. In pursuit of this goal, the study implemented three distinct microtextures on the forefront of the turning tool, each of diverse forms. To comprehensively understand the impact, a 3D model was meticulously constructed for simulation purposes. Subsequently, these microtextures were translated into physical form on the tool’s exterior using laser machining, enabling the researchers to conduct real turning experiments. The experimental phase was designed with precision, maintaining consistent environmental conditions across all tests. The primary focus of these experiments was to investigate the forces generated during the turning process. Additionally, the study explored the stress distribution on the tool’s surface and evaluated the texture of the workpiece after machining. The findings revealed valuable insights into the role of microtextures in altering stress dynamics. Specifically, a tool featuring microtexture on its front exhibited a reduction in stress values, strategically shifting the stress focus from the tool’s tip to the microtexture location on the forefront. Moreover, concerning the texture of the workpiece’s surface post-machining, the tool with parallel groove microtexture demonstrated a noteworthy 21% decrease in surface roughness. The study highlighted the pivotal role of surface microtextures in shaping the performance of a lathe tool. These microtextures were identified as agents capable of modifying the immediate friction between the tool and its chip, thereby diminishing surface friction, cutting force, and post-machining surface roughness. The operational stability of lathe machining was also enhanced through these microtextures. Notably, the microtexture characterized by parallel grooves demonstrated a significant improvement in chip-guiding capacity by aligning with the chip flow direction during cutting. The presented research provided a nuanced understanding of how microtextures on a lathe tool’s surface can be strategically employed to optimize cutting performance, offering potential advancements in the field of machining technology.

Machine learning for predicting laser ablation groove characteristics in polycrystalline diamond

This paper explores machine learning’s role in predicting laser-machined micro-groove texture on Polycrystalline Diamond (PCD) surfaces. PCD has been used for manufacturing ideal cutting insert due to its exceptional attributes, including hardness and thermal conductivity. Surface micro-texturing enhances accuracy and tool lifespan through micro-textures on tool surfaces. Laser micromachining, especially for its precision and efficiency, stands out among methods. Six regression models—Elastic Net, Random Forest, Gradient Boosting Regression, XGBoost Regression, Bayesian Regression, and Gaussian Process Regression—are used to predict groove depth and width based on laser parameters like energy, defocus, and speed. Experiments involve a nanosecond laser system and a commercial PCD tool. Results indicate both Gradient Boosting and XGBoost excel in predicting micro-groove texture. XGBoost slightly outperforms, credited to its enhancements over Gradient Boosting. This paper concludes that machine learning models, especially XGBoost and Gradient Boosting, effectively forecast micro-groove features on laser-machined PCD surfaces, offering insights for further research and practical applications in this domain.

Performance evaluation and comparison of different types of full and partial texture of hydrostatic bearings

To reveal the influence of the different types of surface microtexture on the performance of hydrostatic bearing, microtexture (square, cylindrical, and composite texture) on the inner surface of the bearing were designed. The finite element model of bearing with textures was established. Under the condition of considering the cavitation effect, the influence of the different types of microtexture on performance of the bearing is studied based on the N-S equation. The SEA9 spindle rotation error analyzer is used to determine the eccentricity of the spindle in the machining process and to verify the accuracy of the theoretical simulation. The results demonstrates that the microtexture enhances the performance of hydrostatic bearing, when the eccentricity is in the range of 0∼0.3, compared with square, cylindrica, and smooth bearing, the performance of composite texture bearing can effectively improve the load capacity and reduce the friction coefficient. When the eccentricity is larger than 0.3, the partial textured bearing is analyzed. The initial angle is 120°, the load capacity of the partial microtextured bearing are greater than full microtextured bearing and smooth bearing, which can be used to improve the performance of the bearing. The optimal combination of structural parameters for the performance of the partial composite texture is provided, which has important theoretical significance and practical value for expanding the application range of the spindle system.

Effect of microtexture morphology on the tribological properties of PI/EP-PTFE-WS2 coating under starved oil and dry sliding wear

The limited wear resistance of aluminum alloys constrained their applications and longevity. Surface microtexture combined with polymer coating technology can prolong the service life of aluminum alloy materials under extreme conditions of aerospace. A370 aluminum specimens were textured with three types of microtexture surfaces including circular pits, rectangular grooves and cross grids. A PI/EP-PTFE/WS2 coating was designed and prepared on the surfaces of these textures by liquid spraying to improve the tribological properties of A370 aluminum under starved oil and dry sliding wear. The influences of different micro-texture morphology on the tribological performances of these coatings were experimented. The results indicated that the surface qualities of the micro-textures are improved by coating deposition on their surfaces. The friction coefficients of the coated surfaces on all micro-texture are effectively reduced under the relatively stable wear stage compared to the sample without micro-texture coating. The coating on the pitted texture exhibits superior performance in friction tests, reducing average coefficients and wear rate by 13.58% and 35.34% in dry sliding wear, and by 16.18% and 83.98% under the starved oil lubrication compared to the non-textured substrate, respectively. This is followed by the coating on cross-mesh texture and the rectangular groove texture. The reason is that the pitted texture facilitates the local stress release of coating during the process of coating deposition due to its smaller spacing between pits and higher density of pits per unit area. The bearing capacity of the pitted texture is highest and its deformation is the lowest. The wear debris created in the friction process is more easily accumulated in the pit units, which results in a reduction in wear.

Scale-dependent wetting behavior of bioinspired lubricants on electrical discharge machined Ti6Al4V surfaces

The relationships between the geometric features of material surfaces and topographically related phenomena, such as wetting, change with the scale of observation. In these studies, multiscale analyzes allow characterizing the relationships between electrical discharge machining parameters, complex surface topographic structures and contact angles. Importantly, it was possible to indicate the best scales for observing the phenomena of lubricant flow on electro-discharged surfaces and to identify key geometric parameters of the surface affecting the contact angle. This paper proposes scale-dependent contact angle analyzes of electro-discharge machined Ti6Al4V alloy for biomedical implant applications. Liquids imitating synovial fluid in joints were used as lubricants. The research focuses on comparing the impact of discharge energy on surface microtexture, chemical composition, contact angle and surface free energy. The analysis of the lubrication behavior on micro-textured surfaces in contact mechanics co-determines the tribological properties. The research results confirm the effectiveness of modeling the specific wettability of implant surfaces with bioinspired lubricants.

Influence of micro-texture radial depth variations on the tribological and vibration characteristics of rolling bearings under starved lubrication

Surface micro-texturing involves creating microscopic pits or textures, serving as lubricant reservoirs to enhance lubrication distribution, potentially reducing friction and wear. This study specifically delves into the influence of varied depth patterns of pits on the operational performance of textured rolling bearings under severe lubrication conditions. Five distinct patterns with a fixed pit diameter (250 µm) and different depth variations (concave, decreasing, increasing, convex, and horizontal) were introduced on the shaft rings of cylindrical roller thrust bearings using the laser marking method. Wear tests were conducted under starved lubrication condition. Wear loss and signal analysis highlight the profound effect of depth variations, whereby bearings with shallow pits near the outer side of their working surfaces exhibit longer lubrication times, improved tribological performance, and enhanced vibration characteristics. Notably, the convex pattern stands out for providing comprehensive and favorable tribological and vibration properties. This research contributes valuable insights for the optimal design of micro-textures for rolling bearings, paving the way for enhanced efficiency and reliability in mechanical systems.

Predicting droplet detachment force: Young-Dupré Model Fails, Young-Laplace Model Prevails

Liquid droplets hanging from solid surfaces are commonplace, but their physics is complex. Examples include dew or raindrops hanging onto wires or droplets accumulating onto a cover placed over warm food or windshields. In these scenarios, determining the force of detachment is crucial to rationally design technologies. Despite much research, a quantitative theoretical framework for detachment force remains elusive. In response, we interrogated the elemental droplet–surface system via comprehensive laboratory and computational experiments. The results reveal that the Young–Laplace equation can be utilized to accurately predict the droplet detachment force. When challenged against experiments with liquids of varying properties and droplet sizes, detaching from smooth and microtextured surfaces of wetting and non-wetting chemical make-ups, the predictions were in an excellent quantitative agreement. This study advances the current understanding of droplet physics and will contribute to the rational development of technologies.

Performance analysis of columnar convex-concave compound microtexture thrust bearing

PurposeThis study aims to enhance the lubrication performance of thrust bearings. The influence of columnar convex–concave compound microtexture on bearing performance is investigatedDesign/methodology/approachBased on the compound microtexture model of thrust bearings, considering surface roughness and turbulent effect, the variation of lubrication characteristics with the change in the compound microtexture parameters is studied.FindingsThe results indicate that, compared with circular microtexture, the maximum pressure of compound microtexture of thrust bearings increases by 7.42%. Optimal bearing performance is achieved when the internal microtexture depth is 0.02 mm. Turbulent flow states and surface roughness lead to a reduction in the optimal depth. The maximum pressure and load-carrying capacity of the bearing decrease as the initial angle increases, whereas the friction coefficient increases with the increase in the initial angle. The lubrication performance is best for bearings with a circumferential parallel arrangement of microtexture.Originality/valueThe novel composite microtexture with columnar convex-concave is proposed, and the computational model of thrust bearings is set. The influence of surface roughness and turbulent flow on the bearing performance should be considered for better conforming with engineering practice. The effect of microtexture depth, arrangement method and distribution position on the lubrication performance of the compound microtexture thrust bearing is investigated, which is of great significance for improving tribology, thrust bearings and surface microtexture theory.

Enhancing the reliability of laser welded-brazed aluminum/stainless steel joints via laser-chemical hybrid surface texturing

Surface microtexture is a promising technique for enhancing the quality of heterogeneous joints. This study developed a novel surface texturing method to improve the reliability of laser welded-brazed aluminum/stainless steel joints. The method combined laser etching and chemical etching to create high-quality multi-scale surfaces with large grooves and small wrinkles. The designed microtexture promoted atomic transfer and induced the generation of nanoscale η-Fe2(Al,Si)5 phases during the welding-brazing process. It reduced the spreading activation energy along the groove direction, which enlarged the joining area. It also optimized the strain-stress distribution to enhance the deformation tolerance of the bonding interface throughout the structural strengthening mechanism. Through the synergistic regulation, the joint achieved a maximum line load of 495.9 N/mm, which was 61 % higher than the untextured joint of 307.5 N/mm. The joint performance reached 95 % of the Al/Al lap joint (519.3 N/mm) with the same welding parameters. This study provided new insights into the high-quality joining of aluminum/steel systems or other heterogeneous materials.

Spontaneously formed cellulose-based random micro-textured film for light extraction in organic light-emitting diodes

This study utilized cellulose-based external light extraction films to enhance the outcoupling efficiency of organic light-emitting diodes (OLEDs). These films were created through a straightforward fabrication employing the biopolymers hydroxyethyl cellulose (HEC) and tannic acid (TA). We observed that the hydrogen bonding between HEC and TA could spontaneously generate a random microtextured surface on the HEC: TA films. Furthermore, the surface morphology of the HECTA film can be adjusted by varying the TA content. When applying the HECTA films as an external light-extraction layer for OLEDs, we noticed a remarkable improvement in the external quantum efficiency and current efficiency of the OLEDs up to 54% compared to those without the HECTA film. Additionally, the HECTA film displayed an outstanding ability to absorb ultraviolet light. Therefore, it is anticipated that the HECTA film can significantly contribute to prolonging the stability of OLEDs.

Interfacial heat transfer and melt-front evolution at a Fractal Cantor structured interface under various PCM melting conditions

With the aim to investigate heat transfer characteristics of PCM on micro-textured hot surface, this study numerically investigates the heat transfer process of PCM at fractal Cantor structured surfaces using the total enthalpy-based lattice Boltzmann method, which is partly validated by experimental testing. The thermal slip length and liquid velocity distribution are assessed as evaluation criteria. Results show that Fractal Cantor structure can significantly stimulate localized thermal convection, thereby reducing the average thermal slip length from 0.3 mm to approximately 0.14 mm. When the Fourier number exceeds 0.1, both thermal conduction and convection should be considered within the melted layer. With the fractal level increasing, a more uniform melt-front evolution can be observed, consequently, minimizing the total melting time by 500 s with the fractal level of 3. Elevating Ste and gravity can significantly increase the flow rate of liquid PCM by augmenting superheat degree and buoyancy effect, thereby enhancing convective heat transfer strength and reducing thermal slip length. According to the orthogonal design, though the fractal level demonstrates minimal range values for both maximum velocity and Rayleigh number, it elevates the sensitivity to the variation of boundary conditions. Ste yields the most significant enhancement in heat transfer performance.

Research on Machinability of Dry Cutting 7075 Aluminum Alloy with TiN Coating Micro-Texture Turning Tool

This document suggests a cutting technique for coating the surface of micro-textured structural tools, aiming to tackle the challenges in machining aluminium alloy materials that are hard to machine and simple to soften and stain at elevated temperatures. Initially, considering the varied conditions of cutting dosage during the process caused by diverse forces, the favored parameters for cutting are; next, creating two distinct phases of the micro-texture for application on the tool’s surface, conducting cutting simulation tests with the previously mentioned ideal parameters to evaluate these micro-texture structures in enhancing tool efficiency; ultimately, the focus is on the optimal surface coating of the micro-texture tool to examine how the coating material enhances at the tool’s cutting temperature. Studies have shown that the effectiveness of concave elliptical micro-textured tools in decreasing cutting force and temperature is markedly superior to that of convex elliptical micro-textured tools; experiments revealed that applying a coating to the concave elliptical micro-textured surface of the tool markedly enhances the friction level of both the cutting tool’s front surface and the workpiece’s cutting layer in dry cutting scenarios, thereby decreasing the cutting temperature and chip damage, markedly enhancing the aluminium alloy material’s ability to heat stain the tool.

Effect of surface peak-valley features on the fluid flow performance in rough contact interface

In this work, two kinds of microtextured surfaces with different surface peak-valley features, namely positively skewed surface with micropillar array and negatively skewed surface with micropit array, are prepared to explore the effect of peak-valley features on the fluid flow performance in rough contact interface. The distribution and connectivity of microchannels is analyzed, and the physical mechanism of peak-valley features inducing different fluid flow processes is also derived through constructing a kinetic model of fluid spreading. It is found that when the surface skewness Ssk > 0, the positively skewed surface forms the void regions with better connectivity in the interface compared with the negatively skewed surface (Ssk < 0), despite both the surfaces having nearly the same roughness (Sa ∼ 3.6 mm). The formed microchannels are defined as crossed open microchannel and semi-closed microchannel, respectively, and the feature length of the microchannel decreases with the increase in load. The quantitative results of fluid flow demonstrate that the liquid has a better spreading and flow ability in the contact interface of the positively skewed surface. Even under the same microchannel feature length (nearly 48 mm), the fluid spread area ratio of the positively skewed surface has an order of magnitude higher than that of the negatively skewed surface. The mechanism of different flow characteristics induced by surface peak-valley features is believed as the variation of the microchannel shape, leading to the change in the capillary pressure at the meniscus. We believe the present work would lay a theoretical foundation for regulating the microscopic flow behavior in the contact interface.

Construction of irregular and high-density microtexture on ultra-thin 304 austenitic stainless steel strip via laser surface treatment to improve steel/epoxy resin adhesive bonding properties

Ultra-thin steel strip can be used in composite materials to create high-performance and low-deadweight components for the aerospace industry. The present study used a laser to create surface microtextures on 304 austenitic ultra-thin stainless steel (SS) strips to improve their adhesion to epoxy resin. Modification was conducted at various laser power levels, resulting in ring-like textures of various qualities. The strips were bonded to epoxy resin at single-lap joints, which were then strength-tested. The bonding mechanisms were investigated via analyses of microstructure, surface chemical composition and interfacial failure modes. The laser power level affected the density and distinctiveness of the ring-like structures. The optimal level of 40 W produced a bond with a shear strength of 14.43 MPa. Bonding is enhanced by the interlocking effect of the texture, improved wettability between the steel and epoxy resin, and –C–O=C polar bonds. Lower and higher power levels provided weaker textures. In summary, irregular laser surface treatment can optimize the shear strength of SS–epoxy-resin joints, allowing the fabrication of stronger componentry.

Enhancing soot oxidation using microtextured surfaces

Biomass combustion provides energy needs for millions of people worldwide. However, soot accumulation on the combustors’ walls significantly reduces heat transfer efficiency. Herein, we demonstrate how microtextured surfaces minimize soot accumulation by enhancing soot oxidation. We investigate soot layers from the combustion of paraffin wax as a model for wood-based soot, and find that randomly microtextured glass obtained by sandblasting shows a 71% reduction in the time taken to oxidize 90% of surface soot coverage when compared to smooth glass at 530 °C. We also study grooved microtextures fabricated via laser ablation and find that grooves with widths between 15 and 50 µm enhance soot oxidation, while the expedited advantage is lost when the groove width is 85 µm. X-ray photoelectron spectroscopy validates the superior extent of soot removal on microtextures down to a sub-nanometer length-scale. The high density of sharp features such as peaks and edges on microtextures, and the conformality of the soot layer to the microtextures contribute to increased soot oxidation. We also demonstrate enhanced soot oxidation on microtextured stainless steel, the principal material of construction in biomass combustors. Microtextured surfaces that facilitate soot oxidation upon contact could significantly improve performance and longevity in various combustion applications.

Breast implant surface topography triggers a chronic-like inflammatory response.

Breast implants are extensively employed for both reconstructive and esthetic purposes. However, the safety of breast implants with textured surfaces has been questioned, owing to a potential correlation with anaplastic large-cell lymphoma and the recurrence of breast cancer. This study investigates the immune response elicited by different prosthetic surfaces, focusing on the comparison between macrotextured and microtextured breast implants. Through the analysis of intraoperatively harvested periprosthetic fluids and cell culture experiments on surface replicas, we demonstrate that macrotextured surfaces elicit a more pronounced chronic-like activation of leucocytes and an increased release of inflammatory cytokines, in contrast to microtextured surfaces. In addition, in vitro fluorescent imaging of leucocytes revealed an accumulation of lymphocytes within the cavities of the macrotextured surfaces, indicating that the physical entrapment of these cells may contribute to their activation. These findings suggest that the topography of implant surfaces plays a significant role in promoting a chronic-like inflammatory environment, which could be a contributing factor in the development of lymphomas associated with a wide range of implantable devices.

Capillary Wicking on Heliamphora minor-Mimicking Mesoscopic Trichomes Array.

Liquid spontaneously spreads on rough lyophilic surfaces, and this is driven by capillarity and defined as capillary wicking. Extensive studies on microtextured surfaces have been applied to microfluidics and their corresponding manufacturing. However, the imbibition at mesoscale roughness has seldom been studied due to lacking fabrication techniques. Inspired by the South American pitcher plant Heliamphora minor, which wicks water on its pubescent inside wall for lubrication and drainage, we implemented 3D printing to fabricate a mimetic mesoscopic trichomes array and investigated the high-flux capillary wicking process. Unlike a uniformly thick climbing film on a microtextured surface, the interval filling of millimeter-long and submillimeter-pitched trichomes creates a film of non-uniform thickness. Different from the viscous dissipation that dominated the spreading on microtextured surfaces, we unveiled an inertia-dominated transition regime with mesoscopic wicking dynamics and constructed a scaling law such that the height grows to 2/3 the power of time for various conditions. Finally, we examined the mass transportation inside the non-uniformly thick film, mimicking a plant nutrition supply method, and realized an open system siphon in the film, with the flux saturation condition experimentally determined. This work explores capillary wicking in mesoscopic structures and has potential applications in the design of low-cost high-flux open fluidics.

Simulation and analysis of micro-textured rough curved surface based on fractal characterization method

PurposeMicro-texture is processed on the surface to reduce the friction of the contact surface, and its application is more and more extensive. The purpose of this paper is to create a texture function model to study the influence of surface parameters on the accuracy of the simulated surface so that it can more accurately reflect the characteristics of the real micro-textured surface.Design/methodology/approachThe microstructure function model of rough surfaces is established based on fractal geometry and polar coordinate theory. The offset angle θ is introduced into the fractal geometry function to make the surface asperity normal perpendicular to the tangent of the surface. The 2D and 3D contour surfaces of the surface groove texture are analyzed by MATLAB simulation. The effects of fractal parameters (D and G) and texture parameter h on the curvature of the surface micro-texture model were studied.FindingsThis paper more accurately characterizes the textured 3D curved surface, especially the surface curvature. The scale coefficient G significantly affects curvature, and the influence of fractal dimension D and texture parameters on curvature can be ignored.Originality/valueThe micro-texture model of the rough surface was successfully established, and the range of fractal parameters was determined. It provides a new method for the study of surface micro-texture tribology.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-09-2023-0298/