Surface Texture Design Research Articles

Effect of Square Texture on Tribological Properties of Nano-SiO2/POB-PTFE Composites

In order to study the seal design problem of piston rings in Stirling engine, on the basis of filling PTFE with Nano-SiO2 and POB and preparing the GCr15 contact surface with square texture by HM20-I laser marking machine, experiments were carried out on LSR-2M wear tester by indirect weighing and in-situ observation methods. Optical microscope (OM) and scanning electron microscope (SEM) were used to observe the evolution of Nano-SiO2/POB-PTFE composites’ transfer film on contact surface. The results showed that the square texture would shorten the running-in and transitionary periods of the composites’ tribological process, accelerate into the stationary period. The formation process of the composites’ transfer film on the square textured contact surface was also different from smooth contact surface. Although the square texture would increase wear rate, its ability to store wear debris is more conducive to the formation of reliable, uniform and continuous transfer film with a same friction direction. Obviously, reasonable design of surface texture can effectively improve the wear resistance of sealing parts made of filling modified PTFE composites, thus providing theoretical guidance for the seal design of Stirling engine piston ring.

Water vapor condensation on binary mixed substrates: A molecular dynamics study

Sophisticated and expensive surface texture design and manufacturing are commonly needed to achieve efficient surfaces with enhanced condensation performances. The high nucleation rate and high droplet removal capacity of a substrate surface acquire trade-off, whose mechanisms have not explicitly been comprehended. Based on the assumption that hydrophilic spots would improve nucleation while a hydrophobic surface can facilitate droplet removal rate, this work studied the nucleation and departure processes on a binary mixed substrate with randomly distributed hydrophilic atoms, with homogeneous substrates being as comparison references. The molecular dynamics simulation results showed that the wettability of the binary mixed substrate could be estimated by the form of the Cassie equation. Unlike the randomly nucleated clusters on a homogeneous substrate, the surface energy analysis verifies that the clusters tend to form on the areas with enriched hydrophilic atoms on a binary mixed substrate. Conversely, the droplets also tend to stick on the hydrophilic areas to deteriorate droplet removal efficiency. Combined with a probability analysis by the Monte Carlo method and MD simulation, a moderated ratio(rm = 25% in this work) was shown to furnish better nucleation properties with minimal deterioration in departure properties than the mono-wettability substrate with the same contact angle.

Towards understanding and controlling of the surface texture pattern in 5-axis ball-end milling using fast texture simulation

Surface texture is critical for the functionality of industrial parts. This work aims to effectively control the surface texture by applying the phase difference angle between adjacent cutting passes using 5-axis ball-end milling. Because the texture pattern is complicated and is formed by combining feed-interval and step-interval scallops, we propose a level-contour-based fast simulation method to effectively generate the surface texture by inputting the phase difference angle with tilt and lead angles of the cutter. After clarifying the influence of these three parameters on the texture pattern, the desired texture was controlled by modifying the tool path according to the simulated phase difference angle. As a result, the milled surface texture corresponded well with the simulation. The details of the cutting features were efficiently and comprehensively simulated. The mechanism underlying the sudden change in the texture ridge direction was clarified as the major-minor ridge transition when the phase difference angle increased to a certain level, wherein the surface roughness could be decreased because the rearrangement of the cutting region reduced the scallop height. The proposed fast simulation method was also applied to the optimization process with a case study to demonstrate the benefits it can bring to the surface texture design and control.

Emerging Intercalation Cathode Materials for Multivalent Metal‐Ion Batteries: Status and Challenges

Multivalent metal‐ion (Mg2+, Zn2+, Ca2+, Al3+) batteries emerge as promising alternatives to current lithium‐ion batteries (LIBs) for grid‐scale energy storage applications because of their high safety and low cost. The bright prospect of these batteries encourages increasing research interests in recent years, hence inspirational achievements have been made over the years. Like in LIB, cathode is the most important component that determines the performance of multivalent metal‐ion batteries. Nevertheless, the development of cathode materials still faces realistic challenges, including sluggish solid‐state diffusion and slow desolvation process at the cathode/electrolyte interface. Herein, recent progresses in intercalation cathode materials for multivalent metal‐ion batteries, including vanadium and manganese oxides and their derivatives, chalcogenides, polyanions frameworks, carbon materials, MOFs (or COFs) and Mxenes are summarized. The discussions focus on the rational design and engineering of structure, morphology, and surface texture of these cathodes with the aim of revealing the material design principles for multivalent metal‐ion storage. We hope this critical review will provide the readers with a clear understanding of current status and future research directions of intercalation cathodes for multivalent metal‐ion batteries.

A temporospatial histomorphometric analysis of bone density adjacent to acid-etched self-tapping dental implants with an external hexagon connection in the female baboon.

To characterize osseointegration as the percent of bone-implant contact (%BIC) along the surface (0.0mm) as well as at surface profiles 0.5mm and 1.0mm lateral to the implant, determining any differences between early occlusally loaded and non-loaded implants. In ten adult female baboons, 120 dental implants were randomly placed in opposing mandibular and maxillary locations. Eighty sites had two groups of healing (no load) of either 1 (n = 40) or 2 (n = 40) months leading to 3months of functional loading. These sites received full acid-etched surface implants. The 40 control implants represented healing only periods (no load) for 1 (n = 10), 2 (n = 10), 4 (n = 10), and 5 (n = 10) months. These implants were of a vertically split surface texture design (acid-etched and machined). Block sections and photomicrographs were obtained. Blinded histometric analyses determined the %BIC via a superimposed template. The unloaded groups (1, 2, and 4months) had higher %BIC compared to the 5-month group (p < 0.0001). The loaded groups exhibited mean bone densities of 59.2% and 55.5% (1-month healing at 0.5mm and 1.0mm, respectively) and 61.0% and 57.1% (2-month healing at 0.5mm and 1.0mm, respectively) with no significant difference between healing time (p = 0.4118). There was a lateral increase in %BIC in the loaded compared to unloaded groups. The decrease in bone densities at the 5-month unloaded group suggests that there is a critical earlier time period when dental implants should be placed into functional load.

Study on surface texture patterns for improving tribological performance of bioimplants

A new surface texturing design was proposed for improving the tribological performance of bioimplants. Theoretical analysis was conducted to reveal the positive impact of round corner patterns. Experimental results indicated that round corner would significantly reduce the chance of interlocking phenomenon. Orthogonal experiments suggest that triangle pattern with 200 μm side length, 8–10 μm depth, 10% area density and square-distribution mode turns to be most effective in improving tribological performance of textured bioimplants, showing a 50% reduction in friction coefficient and 44.9% reduction in wear rate than that of polished samples. Working mechanisms of surface texturing in bioimplants were also comprehensively studied. It was confirmed that the extra lifting pressure provided by hydrodynamic effect was less than 1% of the ambient pressure. Further investigations proved that the negligible role of hydrodynamic pressure in the textured bioimplants was due to the low viscosity and slow sliding speed. On the other hand, the capacity to trap particles and second lubrication effect were found to be the main working mechanisms. • Interlocking effect could be the failure mechanism for some patten designs in bioimplants. • Only the patterns with round-corner should be adopted in the bioimplants. • Area density is the most influential pattern parameter while the distribution mode is the least one. • Capacity to trap particles and second lubrication effect are the main working mechanisms for textured bioimplants.

A Design of Partial Textured Surface on Gear Washers for Reducing Friction and Wear under Low Speed and Heavy Load Conditions.

This paper presents the effort to reduce friction and wear of gear washers under low-speed and heavy-load conditions by designing the arrangement of surface textures. The influence of distributional parameters of textures on load-bearing capacity and friction coefficient of gear washers are studied numerically to obtain a preferable surface texturing design. Then, experimental tests were carried out to plot the Stribeck curves of the obtained texture arrangement compared with bare surface and another unoptimizable texture distribution arrangement to facilitate the verification of the simulation results. Theoretical predictions illustrate that the annular gear washers with partial surface texturing provide lower friction coefficients than bare washers. Textures having a sector angle of 20°, a coverage angle of 12°, a circumferential number of 8, and a radial number of 6 are selected as the final optimal surface texture distribution design. Experimental results confirm that the obtained texture arrangement moves the Stribeck curve towards the lower left, indicating thickening of oil film thickness and reduction in friction coefficient. In addition, the weight loss caused by wear is also reduced by the optimized texture design.

Influence of micro-nano surface texture on the hydrophobicity and corrosion resistance of a Ti6Al4V alloy surface

PurposeThe purpose of this paper is to study the effect of micro-nano surface texture on the corrosion resistance of a titanium alloy and investigate the correlation between corrosion resistance and hydrophobicity.Design/methodology/approachThe surface of the Ti6Al4V alloy was modified by laser processing and anodizing to fabricate micro-pits, nanotubes and micro-nano surface textures. Afterward, the surface morphology, hydrophobicity and polarization curve of the samples were analyzed by cold field scanning electron microscopy, contact angle measurement instruments and a multi-channel electrochemical workstation.FindingsThe micro-nano surface texture can enhance the hydrophobicity of the Ti6Al4V surface, which may lead to better drag reduction to ease the friction of implants in vivo. Nevertheless, no correlation existed between surface hydrophobicity and corrosion resistance; the corrosion resistance of samples with nanotubes and high-density samples with micro-nano surface texture was extremely enhanced, indicating the similar corrosion resistance of the two.Research limitations/implicationsThe mechanism of micro-dimples on the corrosion resistance of the micro-nano surface texture was not studied.Practical implicationsThe density of micro-pits needs to be optimized to guarantee excellent corrosion resistance in the design of the micro-nano surface texture; otherwise, it will not fulfill the requirement of surface modification.Originality/valueThe influence of the micro-nano surface texture on the corrosion resistance, as well as the relationship between hydrophobicity and corrosion resistance of the titanium alloy surface, were systematically investigated for the first time. These conclusions offer new knowledge.

Optimal design of surface texture in meso scale air journal bearing

Meso scale air journal bearing has widespread application in miniaturized systems and there is a strong need to improve its tribological performance. Although surface texturing can improve its performance, very few studies have addressed this issue. Therefore, this paper investigates the influence of texture geometrical parameters on the tribological performance of meso scale air journal bearing. A numerical study is carried out in a thin-film model of the COMSOL 5.2 package. The effect of texture geometrical parameters viz. position, depth, orientation, and slender ratio on tribological characteristics such as load-carrying capacity and friction coefficient is first analyzed by response surface methodology based Box-Behnken design. Further, a multi-objective optimization study is carried out using grey relational analysis. For the optimum design, textured air bearing has obtained 12.15% more load carrying capacity, and 19.65% lesser friction coefficient than the plane air bearing. For this improvement, texture depth and orientation are found to be the most and the least significant parameters, respectively. Also, at variable bearing parameters such as eccentricity ratio and rotational speed the optimum textured bearing performed better than the regularly textured bearings.

Analysis of convection heat transfer on multiscale rough superhydrophobic and liquid infused surfaces

Multiscale rough superhydrophobic or slippery liquid infused porous surfaces have gained much interest in recent years for their improved transport phenomena properties. While there have been several studies on drag reduction and condensation on non-wetting surfaces, convection heat transfer that is important in many thermal and thermochemical applications has not been addressed systematically. This article utilizes a fractal description of rough surface topographies to develop analytical models for the Nusselt number and the thermal hydraulic factor for fluid flow and heat transfer inside a cylinder with non-wetting surfaces. For air-infused superhydrophobic surfaces, the model considers the dynamic stability of the air/fluid interface in the asperities. Using the analytical formulations and the stability criteria, systematic studies are presented on the effects of the fractal surface parameters, cylinder radius and Reynolds number on the convective heat transfer characteristics, from which surface texture design maps are developed for maximizing the convection heat transfer. It is shown that multiscale non-wetting surfaces are most effective in the range of lower Reynolds number and small cylinder radius for achieving the best convective heat transfer and thermal hydraulic performance. Applying the models to actual non-wetting surface topographies fabricated using electrodeposition and chemical etching, it is shown that contrary to prevailing notion, superhydrophobicity, characterized by the highest contact angles, does not always lead to the maximum convective heat transfer performance, and that under certain fluid flow conditions, hydrophobic surfaces may offer a greater thermal performance.

Investigation on the adhesive contact and electrical performance for triboelectric nanogenerator considering polymer viscoelasticity

The triboelectric nanogenerator (TENG) is a new mechanical energy harvesting technology in which the typical viscoelastic material polydimethylsiloxane (PDMS) is widely used. Micro-/nano-textures are often fabricated on the PDMS surface to enhance the electrical performance of TENG. As the contact region decreases to micro/nano scale, the adhesive forces become dominant. However, there is still a lack of contact mechanics model considering both material viscoelasticity and the adhesive forces to guide the surface texture design. In this paper, the explicit data-fitting formulas based on the fractional derivative Zener model are firstly derived to identify the viscoelastic constitutive parameters, which can not only avoid the influence of the initial contact point, but also ensure the accurate conversion between the creep compliance and the relaxation modulus function. Then a viscoelastic-adhesive contact model based on the fitted constitutive parameters is established, and the numerical algorithms such as bi-conjugate stabilized (Bi-CGSTAB) method and fast Fourier transform (FFT) technique are employed to analyze the effects of material viscoelasticity and texture sizes on the contact and electrical performance. It is shown that, compared with results from the elastic-adhesive contact model, the contact area ratio based on the viscoelastic-adhesive contact model is significantly larger, which is much closer to the experimental results. Among the selected sizes of pyramid texture, the higher electrical performance can be obtained from the textures with a smaller pitch and a larger width under the heavier applied load. This study can provide a theoretical reference for the design of viscoelastic surface texture of TENG.

Hydrodynamic Performance of Positive Surface Textured Patterns under Mixed Lubrication

It is proved that the optimal design of surface textures (positive or negative) improve the lubrication performance by generating extra hydrodynamic pressure at the interface of the sliding pairs. In the present work, the effect of various positive surface textures on hydrodynamic performance of parallel sliding contact under mixed lubrication is researched. The modified Reynolds equation and asperity contact model are solved simultaneously to assess the hydrodynamic pressure and minimum film thickness for different shape of textures. The results depict that elliptical shaped texture generate high hydrodynamic pressure as well as minimum film thickness at the conjunction than the other texture shapes.

Optimization tool based on multi-objective adaptive surrogate modeling for surface texture design of slipper bearing in axial piston pump

A novel multiobjective adaptive surrogate model is employed for the prediction of full-film lubrication performance of surface texture profile for thrust bearings in axial piston pumps. At present, a surface texture optimization design of thrust bearing in axial piston pump has not been provided based on a unique design solutions. In this study, multi-objective adaptive surrogate-based optimization (MO-ASMO) algorithm was used for solving both the mechanical and volumetric losses performance design of surface texture. The non-dominated sorting genetic algorithm (NSGA-II) formed part of the developed multi-objective optimization model, having three competing design objectives which mainly include load capacity, friction torque and leakage rate. A comparative study of two models with accuracy analysis of each case was performed. The results show that the MO-ASMO has the best performance among the different surrogate models. Comparing with the NSGA-II model, the improvement of the leakage rate and the load carrying force made by MO-ASMO are higher about 16.12% and 3.67%, respectively. In other words, multi-objective optimization is capable of enhancing textured slipper bearing performance using MO-ASMO method. The optimal texture radius and texture depth are chosen to minimize the leakage rate and texture bearing capacity.

Finite Element Modelling and Experimental Validation of Scratches on Textured Polymer Surfaces.

Surface texturing is a common modification method for altering the surface properties of a material. Predicting the response of a textured surface to scratching is significant in surface texturing and material design. In this study, scratches on a thermoplastic material with textured surface are simulated and experimentally tested. The effect of texture on scratch resistance, surface visual appearance, surface deformation and material damage are investigated. Bruise spot scratches on textured surfaces are found at low scratch forces (<3 N) and their size at different scratch forces is approximately the same. There is a critical point between the bruise spot damage and the texture pattern damage caused by continuous scratching. Scratch resistance coefficients and an indentation depth-force pattern are revealed for two textured surfaces. A texture named “Texture CB” exhibits high effectiveness in enhancing scratch visibility resistance and can increase the scratch resistance by more than 40% at low scratch forces. The simulation method and the analysis of the power spectral density of the textured surface enable an accurate prediction of scratches.

Wettability Control on YW2 Cemented Carbide Surface by Femtosecond Laser Irradiation

The surface wettability control of cemented carbide tools is beneficial to the improvement of tool life and surface quality of workpieces in wet cutting. To clarify the correlation between the surface topography and wettability, squared microdimples are fabricated on the cemented carbide surface using a femtosecond laser. The dependencies of the side length, the depth, and the distribution density of squared microdimples on the surface topography and contact angle are studied. As the average laser power, and the number of scanning passes, increase, both the side length and depth of the squared microdimples increase. The contact angle decreases from hydrophilic to superhydrophilic. Moreover, the roughness height parameters have a great influence on the surface wettability, the larger the surface arithmetic average height, the smaller the kurtosis, the larger the skewness, and the better the hydrophilicity. The results of the scanning electron microscope (SEM) and energy‐dispersive spectrometer (EDS) reflect that the changes in the micro–nano protrusions, carbon, and oxygen elements cause deviation between the calculated contact angle and the actual contact angle. The friction coefficient of textured tools is lower than that of untextured tools at high sliding speed. Reasonable design of surface texture accurately controls surface wettability.

A comparative study on different textured and untextured tools performance in turning process

ABSTRACT In the turning process, surface quality and tool life significantly depend on the surface texture design, tool geometry, process parameters, and cooling environment. Further, cutting velocity (v) and feed rate (f) have a proportional relationship with productivity. In the past, few attempts were made in turning of AISI 304 under cryogenic, dry, and combination of cryo-MQL conditions with conventional (without texture) tools. In the present research work, different microgroove angles 90° (T-1), 45° (T-2), and 60° (T-3) to the main cutting edge of the tool was prepared on the rake face of the PVD coated tungsten carbide tools, and performed experiments on AISI 304 SS under MQL cooling technique at varying ‘v’ and ‘f’ conditions, respectively. Further, experimental results were compared with untextured tools under MQL and wet cooling, respectively. From the results, the T-1 tool with MQL significantly reduced the surface roughness (Ra), tool wear (Vb), and cutting zone temperature (Tt) when compared to the T-2 tool with MQL, T-3 with MQL, untextured tool with MQL, and untextured tool with wet cooling, respectively, at varying ‘v’ and ‘f’ conditions.

An optimization research on groove textures of a journal bearing using particle swarm optimization algorithm

This study aims to optimize the distributions of groove textures in a journal bearing to reduce its friction coefficient. Firstly, A lubrication model of a groove textured journal bearing is established, and the finite difference and overrelaxation iterative methods are used to numerically solve the model. Then, the friction coefficient is adopted as the fitness function and the groove lengths are optimized by particle swarm optimization (PSO) algorithm to evolve the optimal distributions. Furthermore, the effects of eccentricity ratios and rotary speeds on optimal distributions of groove textures are also discussed. The numerical results show the optimal distributions of groove textures are like trapeziums under different eccentricity ratios and rotary speeds, and the trapeziums become slenderer with increasing of eccentricity ratios. It is also found that the reductions of friction coefficients by optimal groove textures are more significant under lower eccentricity ratios. Briefly, this study may provide guidance on surface texture design to improve the tribological performance of journal bearings.

Surface texture design method using mechanoreceptor stress in finger as evaluation function

Surface texture design method using mechanoreceptor stress in finger as evaluation function

Parametrically designed surface topography on CAD models of additively manufactured lattice structures for improved design validation

Additively Manufactured (AM) lattice structures of the laser powder bed fusion (LPBF) process generally have different surface geometries depending on the overhang angle and location. This means that the design validation stage is often challenging, considering it is based on an ideal Computer Aided Design (CAD) model that is not truly representative, since the AM part will be different in terms of dimensional accuracy and surface finish. Previous studies have relied on the design of surface textures that are independent of the overhang angle, or techniques based on directly using X-ray Computed Tomography (XCT) data. In this paper, a new technique for designing surface texture on the CAD of lattices has been investigated and correlated with areal surface roughness parameters. After extracting areal surface parameters from the XCT data of the lattice, the method allowed for the design of this surface texture on the part CAD taking in consideration if its up skin or down skin, without using XCT data as the main input. By applying this method, it is possible to obtain a lattice CAD model with a designed surface texture and geometry that is more representative of the actual AM lattice. The mean deviation between the CAD model with the designed surface and the XCT was a third of the one between the XCT and the initial CAD. The proposed method allows for designing and replicating LPBF AM surfaces on the CAD of a lattice, taking into consideration the dimensional deviation caused by AM surfaces, especially on overhangs. Assuming that an LPBF AM process is stable and produces approximately the same AM surface, this method can be used to predict the geometry of a lattice, providing a cost-effective and efficient methodology that minimizes the time needed for design validation.

Numerical analysis and optimization of rectangular texture for gas foil thrust bearing

Accurate surface texture design is of great significance to improve the performances of gas bearings. In this article, the finite difference method and Newton’s method were combined to obtain the oil film pressure distribution, and the effect of rectangular groove on the lubrication performance was analyzed by changing representative texture parameters. The results show that the performances were more affected by the rectangular texture size compared with the distribution and the bottom shape of texture. The increasing of the surface texture number can only enhance the stability of the bearing. The bearing can provide 30% more bearing capacity by choosing larger size, radial arrangement and plane bottom. These results and analysis can provide technical reference for the bearing texture design.