Influence Of Surface Roughness Research Articles

Natural dentifrices: how can prolonged toothbrushing influence enamel color and surface roughness?

This study evaluated the color change (ΔE00) and surface roughness (Ra) of enamel submitted to prolonged toothbrushing with natural non-fluoride dentifrices. Five groups of bovine teeth (n=10) were brushed with a control dentifrice: (C) Colgate Total 12 – Colgate; and four natural dentifrices: (R) Restore – Jeunesse; (OG) OnGuard – doTerra; (OC) OzonCare – Philozon; and (N) Natural activated charcoal – Suavetex. Mechanical toothbrushing simulated one month (T1), six months (T2), one year (T3), and two years (T4) of product use. ΔE00 and Ra were measured before and after toothbrushing. Two-way repeated measures ANOVA and Tukey's test were performed. Dentifrice (p<0.001), toothbrushing time (p=0.004), and their interaction (p=0.031) influenced color change (ΔE00). Natural dentifrices promoted similar color change and Ra to the traditional product. After six months of simulated toothbrushing, OG promoted more color changes than N and R. Only OG and R reached ΔE00 above the acceptability threshold. OC and N dentifrices generated Ra above the limit of clinical roughness from T2. Toothbrushing with natural toothpaste for up to two years causes similar enamel color changes and roughness to the traditional product.

A bottom-up multi-physics model correlating burnishing factors to fatigue life

Burnishing is type of contact based non-metal removal finishing processes that is used to enhance the service performance of hard material like Ti-6Al-4V through modification of roughness, exerting work hardened surface layer and inducing compressive residual stress. However, the design of process aiming at anti-fatigue machining is a big challenge, since on one hand the experimental trial and errors of fatigue tests are time consuming and costly, on the other hand there is lack of predictive models that directly correlate the process factors to lifetime. Therefore, to study the fatigue behavior of burnished samples, a holistic predictive framework is required. The present study takes lead to solve the problem by developing a model which correlates the surface integrity and fatigue life of the materials processed. Here firstly the roughness, microhardness and residual stress of the burnished samples are modeled and correlated to process factors through multiphysics of burnishing. Then they were correlated to fatigue life by using stress-based approach that includes surface geometrical, mechanical and metallurgical aspects. The accuracy of developed models were compared with the series of experiments which were carried out on as-turned Ti-6Al-4V. The results revealed that the developed analytical model can predict the lifetime of the burnished samples with acceptable accuracy where the average prediction error for 16 data sets is 13.6 % within the range of 6.3 % to 22 %. The verified model was then utilized to identify the mechanism of lifetime variation and to understand how the process factors determines the fatigue life. It was obtained that the static force as a parameter contributed to loading has greatest impact on variation of fatigue life by adjusting all the surface integrity aspects i.e. roughness, microhardness and residual stress. It was also found that the main impact of feed rate on fatigue life is attributed to its influence surface roughness at high static force.

From creep to flow: Granular materials under cyclic shear

When unperturbed, granular materials form stable structures that resemble the ones of other amorphous solids like metallic or colloidal glasses. Whether or not granular materials under shear have an elastic response is not known, and also the influence of particle surface roughness on the yielding transition has so far remained elusive. Here we use X-ray tomography to determine the three-dimensional microscopic dynamics of two granular systems that have different roughness and that are driven by cyclic shear. Both systems, and for all shear amplitudes Γ considered, show a cross-over from creep to diffusive dynamics, indicating that rough granular materials have no elastic response and always yield, in stark contrast to simple glasses. For the system with small roughness, we observe a clear dynamic change at Γ ≈ 0.1, accompanied by a pronounced slowing down and dynamical heterogeneity. For the large roughness system, the dynamics evolves instead continuously as a function of Γ. We rationalize this roughness dependence using the potential energy landscape of the systems: The roughness induces to this landscape a micro-corrugation with a new length scale, whose ratio over the particle size is the relevant parameter. Our results reveal the unexpected richness in relaxation mechanisms for real granular materials.

Influence of Surface Roughness on Symmetric Airfoil Flow Properties and Reynolds Number

Collaborative Aircraft Design Optimization: Investigating Roughness Management of Wings to Reduce Drag and Improve Performance This study investigates the potential of roughness control of aircraft wings based on joint design optimization. By adding roughness points to specific wings, our goal is to reduce drag and improve the overall performance of the aircraft. A multi-modal design optimization (MDO) framework combining aerodynamics, modelling, and performance analysis was used in this study. We measure the effect of tissue on the boundary layer, the progression of laminar flow, and the potential for weight savings due to reduced friction. This study investigates how roughness control interacts with other design factors such as flow components or blade materials to achieve optimal performance. The ultimate goal is to create a collaborative design that uses tissue management to contribute to next-generation fuel efficiency and high performance. Keywords – CFD, Surface Roughness, Wind Tunnel, Aerodynamic Efficiency.

Ship Flow of the Ryuko-maru Calculated by the Reynolds Stress Model Using the Roughness Function at the Full Scale

The k-omega SST turbulence model is extensively employed in Reynolds-averaged Navier–Stokes (RANS)-based Computational Fluid Dynamics (CFD) calculations. However, the accuracy of the estimation of viscous resistance and companion flow distribution for full-sized vessels is not sufficient. This study conducted a computational analysis of the flow around the Ryuko-maru at model-scale and full-scale Reynolds numbers utilizing the Reynolds stress turbulence model (RSM). The obtained Reynolds stress distribution from the model-scale computation was compared against experimental measurements to assess the capability of the RSM. Furthermore, full-scale computations were performed, incorporating the influence of hull surface roughness, with the resulting wake distributions juxtaposed with the actual ship measurements. The full-scale calculation employed the sand-grain roughness function, and an optimal roughness length scale was determined by aligning the computed wake distribution with Ryuko-maru’s measured data. The results of this study will allow for the direct performance estimation of full-scale ships and contribute to the design technology of performance.

Investigation of surface roughness effects on the dynamic performance of electromagnetic nano-resonators

Here, we expose the influence of surface roughness on the dynamics of electromagnetic nano-resonators. To this end, the continuum field equations of an electromechanical nano-resonator subjected to an external magnetic flux are formulated. The developed model considers surface integrity, including surface roughness, waviness, and altered layer. Also, the influence of residual stresses of the extreme surfaces of the resonator is incorporated in the proposed model. It was revealed that the surface roughness significantly tailors the dynamic stability of the resonator, as the voltage that onsets the pull-in instability of the resonator decreases as the surface roughness increases, which thus indicates the necessity of particular calibrations of nano-resonators for surface roughness. To investigate the problem and the effect of factors such as magnetic field intensity, roughness, and beam surface thickness on the pull-in voltage, we have performed an analysis using the Taguchi method and analysis of variance. The results show that the intensity of the magnetic field has the most significant effect on pull-in voltage. Also, the more accurate results show on the resonance frequency; with the increase of the input voltage to the beam, the impact of increasing the intensity of the magnetic field and other factors increases. The rest of the paper proposes a linear and non-linear model to express the pull-in voltage according to the investigated factors.

Surface roughness characterization of additive manufactured Ti-6Al-4 V based on laser ultrasonic signal

Additive manufacturing (AM), especially AM for metals, has become the most promising processing technique in recent years and is widely applied across several industries. Laser ultrasonic testing (LUT) has appeared as a potential method for identifying defects in additive manufactured components, but the rough surface of the additive manufactured component affects the ultrasonic signal. Analyzing the influence of surface roughness on ultrasonic signals and characterizing surface roughness through ultrasonic signals can improve the accuracy of defect detection and monitor the working conditions in the processing, which is a great significance for enhancing the quality of additive manufactured products. In this study, the influence of additive manufactured rough surface with different Ra on the ultrasonic signal has been analyzed. A novel simulation approach for the rough surface was provided, and the created surfaces with different Ra were applied to modeling. The results indicate that when the surface roughness increases, the ultrasonic signals suffer strong diffuse reflection, and the signal energy decreases. When the Ra is small, the surface of the specimen is close to smooth, the reflection of energy is enhanced, and part of the signals are reflected, so the signal energy is slightly lower. The ultrasonic signal of all models has been denoised and reconstructed based on the variational mode decomposition (VMD), and the analytical expression between the reconstructed signal energy and Ra was derived. The laser ultrasonic experiments were further designed for exciting signals from different Ra specimens, and the analytical expression relating reconstructed signals to Ra was also obtained, then the surface roughness of two specimens with unknown Ra was calculated by ultrasonic signals. A new method to obtain the roughness Ra of the additive manufactured components by ultrasonic signal is developed.

The effect of shot peening on the contact fatigue performance of C40 steel gears after laser surface melting

In this paper, shot peening (SP) was employed as a post-processing technique for the laser surface melted (LSMed) gear. The aim was to improve the contact fatigue performance of laser surface melting+shot peened (LSMSPed) gears. The microstructure, surface roughness, residual stress, microhardness of C40 steel gears before and after SP treatment were characterized using scanning electron microscopy, x-ray diffraction stress analyzer, contour measuring instrument, and hardness tester. Fatigue test of gear was carried out with a Forschungsstelle für Zahnräder und Getriebebau (FZG) testing machine. Following the laser surface melting (LSM) treatment, a molten layer was observed on the gear teeth surface. The experimental results indicated that SP induced a hardened layer with a certain thickness and plastic deformation on the surface of LSMed gears. Importantly, as the SP parameters increased, there’s a corresponding reduction in both the average grain diameter and the maximum grain diameter. The reduction was most pronounced when the shot diameter reached its maximum value. It’s worth noting that once the optimal threshold for SP parameters is surpassed, the residual compressive stress and microhardness on the LSMSPed gear surface do not exhibit a continuous growth trend. Furthermore, the rise in SP parameters resulted in a gradual increase in the surface roughness of LSMSPed gears, albeit to varying degrees. In light of the combined effects of grain refinement, residual compressive stress, microhardness, and surface roughness, the contact fatigue performance of LSMSPed gears improved with increasing SP parameters. Notably, when comparing the contact fatigue life of LSMed gears with that of LSMSPed gears, we observed a substantial enhancement. However, it’s essential to highlight that when the shot diameter reaches its maximum value, the contact fatigue life of the LSMSPed gear, somewhat unexpectedly, decreased. It emphasized to a certain extent the influence of surface roughness on the contact fatigue performance of LSMSP gears.

Highly transparent and highly hydrophobic coating for outdoor camera window glass: Fabrication, transparency, and hydrophobicity

Highly transparent, superhydrophobic coatings are highly desirable for maintaining long-lasting clarity for outdoor camera windows. In this study, the authors present a simple approach to create a wide–range anti-reflective and highly hydrophobic layer on a glass surface. This is accomplished through a hydrothermal alkali etching process combined with a dip-coating process using 1H, 1H, 2H, 2H-Perfluorooctyltrimethoxysilane (POTS). The sample, etched for 20 hours and modified by POTS, exhibiting an average transmittance of 96.5%, a water contact angle (WCA) of 140o and a sliding angle (SA) of 40o. The results of the water spray experiment indicate this surface exhibits excellent water repellent performance, preventing water droplets larger than 0.01 mm in size. The relationship between optical transmittance and etching depth was thoroughly studied, revealing that an etched depth ranging from 200 nm to 600 nm yields optimal wide-spectrum anti-reflective properties. Furthermore, the influence of surface roughness on apparent WCA and SA was investigated. It was found that root mean square (RMS) roughness can be an effective factor to predict the apparent WCA of a surface, while both the RMS roughness and morphological structure affect the SA.

Faraday rotation stimulated optical rotation quasi-phase-matching technique to radiate highly efficient elliptically polarized second harmonic

Faraday rotation stimulated optical rotation quasi-phase-matching technique to radiate highly efficient elliptically polarized second harmonic

Influence of Surface Roughness on Durability of New-Old Concrete Interface

The bond zone between old and new concrete is greatly affected by environmental factors. This study investigates the impact of surface roughness on durability using as-cast surface (CS), drilled holes surface (DS), and grooved surface (GS). After a 28-day water-curing, specimens undergo a 5% NaCl solution immersion for 30 and 60 days; exposure to temperatures of 200 ℃ and 500 ℃; and a water permeability test. Slant shear and splitting tensile tests assess durability. Results show that CS exhibits the greatest decrease in resistance to sodium chloride solution and temperature, while DS and GS show less pronounced effects. At 500 ℃, CS and DS specimens fail, whereas GS retains 50% and 75% of its shear and tensile strengths, respectively. GS has the lowest water permeability (7 × 10-11 m/s), followed by DS (1.2 × 10-10) and CS (1.5 × 10-10). Overall, surface roughness enhances durability and mitigates environmental effects.

Influence of surface roughness and tensile bond strength in clay hollow block-paste adhesion

Influence of surface roughness and tensile bond strength in clay hollow block-paste adhesion

Superior interface adhesion and protective mechanism of room-temperature-curable polymer composite coating on engineering substrates with lower roughness

In view of the technology bottleneck of the adhesion failure of traditional functional protective coatings on the smoother surface of precise parts served in the marine atmosphere, a room-temperature-curable fluoropolymer/polyurethane (denoted as RFP) polymer composite coating of 20–30 μm is prepared on the metal substrates. Static pull-off and dynamic friction test methods are used to evaluate the interface adhesion of the coating. The coating shows superior adhesive strength of 18–24 MPa on a variety of metal substrates with a wide range of surface roughness (Ra = 0.1–1.6 μm). The friction coefficient of the coating surface is about 0.05–0.08, and the wear life is up to 9–12 km/μm. Furthermore, the adhesion strength of the coating remains 12–14 MPa after 1600 h of salt spray while the wear life of the coating keeps 3–9 km/μm after 720 h of salt spray. The influences of surface roughness (Ra), surface free energy (γOxide), surface potential (φOxide) of the metal substrates and the bonding force at substrate-coating interface on the adhesive energy (Eadh.) are discussed, and the mechanism of "physical-chemical-surface" synergetic enhanced interface adhesion is proposed. The RFP coating is used as the intermediate layer for traditional PU and EP coatings to improve their adhesion on smooth aluminum substrate from 1.39 MPa to 17.5 MPa (increased by 1260 %). Thus, the polymer coating has the potential to provide technical support for the development of long-term anticorrosive coating technology for precision components of marine high-tech equipment.

The case study of the surface roughness influence at additively manufactured ejector and orifice plate and its impact on fluid flow

ABSTRACT Energy consumption and economic growth are strongly linked. In connection, great emphasis is nowadays placed on the accuracy and efficiency of machines and measuring equipment. This study compares the effect of surface roughness on airflow through a gas ejector and a centric orifice plate. Both devices are made from the same material but using two different methods of manufacturing, conventional and additive manufacturing. The study compares, experimentally and with numerical simulation, the subcritical ejector by adjusting the distance between the nozzle outlet and the mixing chamber outlet in the range of 16.9 mm, during the primary inlet pressure control from 10 to 50 kPa. The orifice is evaluated experimentally for different pressures from 0.6 to 7 bar(g). The study evaluates the level of substitutability of conventionally manufactured devices by those produced using the additive method. At design condition, the additively manufactured ejector exhibits a 12.97% lower ejection coefficient, i.e. lower effectivity. After control optimization, the decrease is reduced to 11.66%. For the additively manufactured orifice, the measured value of the pressure difference at nominal parameters deviated by 2.17%. In the case of the orifice, substitution is possible, assuming the calibration, but the orifice has a higher-pressure loss.

Influence of surface roughness on the fluid flow in microchannel

Surface roughness is a crucial factor of fluid flow in microfluidic channels. Most of the existing studies focus on the effect of regular microstructured surfaces on fluid flow, while researchs about the impact of random rough surfaces on fluid flow remains limited. Therefore, in this study, a random rough surface model and two microstructured surface models were established, and the effects surface roughness on the fluid flow at Wenzel state and Cassie-Baxter state were studied using COMSOL multi-physics simulation software. Our findings reveal that both the flow velocity and the fluid flow rate at the microchannel outlet decreases with the surface roughness increases. Notably, the flow rate and velocity of the fluid flow at Cassie-Baxter state is higher than that of fluid flow at Wenzel state.

Improvement of Methods and Devices for Multi-Parameter High-Voltage Testing of Dielectric Coatings

Currently, the high voltage testing method is widely used to detect pinholes and porosity defects in dielectric coatings. However, most modern coatings also have requirements for the minimum allowable coating thickness. Conducting tolerance tests on the thickness of dielectric coatings concurrently along with monitoring integrity within a single technological process appears promising. Additionally, mitigating the impact of various interfering parameters is crucial. This paper conducts a theoretical and experimental examination of spark formation processes in both gas and dielectrics. This analysis takes place during the identification of both through and non-through defects in dielectric coatings on conductive substrates. The principles of selecting the test voltage for the investigated dielectric coatings, considering the need to detect both through defects and inadmissible thinning, are theoretically and experimentally justified. It is suggested to utilize a probabilistic approach for evaluating the detectability of the mentioned defects. It is demonstrated that, when the dielectric strength of the coating is known, it is feasible to identify both through and non-through defects in coatings with a calculated probability under a specified test voltage. The conditions of occurrence of partial discharges in the process of testing are investigated, and measures to suppress their influence on the inspection results are proposed. The influence of the substrate surface roughness on the magnitude of the breakdown voltage during testing is considered.

Multi-axis CNC finishing and surface roughness prediction of TC11 titanium alloy open integral micro impeller

The titanium alloy open integral micro impeller has a strong material strength and high removal rate in the field of multi-axis CNC machining. The flow channel is tiny and the blades are thin and highly twisted. It is difficult to control the surface accuracy and prone to overcutting and undercutting. The NX2212 software post-processing module plans two distinct blade finishing process routes and verifies them using virtual machine tool simulation, taking into account the technical challenges of micro impeller machining. Following verification, the tool path machining code is imported into MATLAB for data fitting. The workpiece surface working condition is determined based on the simulation findings, the blade surface roughness value is calculated, and a physical simulation model of blade finishing is created in the finite element analysis software. The outcomes demonstrate how well the “segmented and sub-regional cutting” processing method may raise blade accuracy. The leading and trailing edges of the blade both had surface roughness increases of 4.86% and 4.19%. The surface morphology of the micro impeller is measured using a white light interferometer, and it is CNC machined using two distinct process methods. The findings demonstrate that there is a significant difference between the value calculated by the finite element analysis software and the surface roughness value measured experimentally which together make up less than 5%. An investigation of the impact of cutting parameters on the surface roughness of micro-structure components is carried out using a three factor, three-level BBD experiment that is founded on the second-order response surface method. The findings indicate that the feed per tooth influences surface roughness more significantly than cutting depth and cutting speed for a reasonable range of cutting parameters; Surface roughness will rise with lower or higher cutting speeds; Raising the feed per tooth and the cutting speed simultaneously may reduce surface roughness; Surface roughness can be accurately predicted and controlled using the second-order response surface method.

Processing and cytocompatibility of Cu-doped and undoped fluoride-containing bioactive glasses

Sintered or additive-manufactured bioactive glass (BG) scaffolds are highly interesting for bone replacement applications. However, crystallization often limits the high-temperature processability of bioactive glasses (BGs). Thus, the BG composition must combine high bioactivity and processability. In this study, three BGs with nominal molar (%) compositions 54.6SiO2-1.7P2O3-22.1CaO-6.0Na2O-7.9K2O-7.7MgO (13–93), 44.8SiO2-2.5P2O3-36.5CaO-6.6Na2O-6.6K2O-3.0CaF2 (F3) and 44.8SiO2-2.5P2O3-35.5CaO-6.6Na2O-6.6K2O-3.0CaF2-1.0CuO (F3–Cu) were investigated. The dissolution and ion release kinetics were investigated on milled glass powder and crystallized particles (500–600 μm). All glasses showed the precipitation of hydroxyapatite (HAp) crystals after 7 days of immersion in simulated body fluid. No significant differences in ion release from glass and crystalline samples were detected. The influence of surface roughness on cytocompatibility and growth of pre-osteoblast cells (MC3T3-E1) was investigated on sintered and polished BG pellets. Results showed that sintered BG pellets were cytocompatible, and cells were seen to be well attached and spread on the surface after 5 days of incubation. The results showed an inverse relation of cell viability with the surface roughness of pellets, and cells were seen to attach and spread along the direction of scratches.

Selective ion permeation enables reduced combined gypsum-organic fouling of loose nanofiltration membranes

During the long-term operation of NF membranes, the occurrence of combined gypsum-organic fouling is a significant challenge. While numerous studies have focused on enhancing the fouling resistance of NF through various methods (e.g., antiscalants, pretreatment), there has been limited exploration into the correlation between its structural looseness and fouling resistance. Herein, we conducted an experimental study to evaluate the correlation by employing three NF membranes with different looseness degrees: a custom-developed loosely structured NF membrane (CLNF), the moderately loose NF270, and the tightly structured NF90. Our findings indicated that NF membranes with loose polyamide structure exhibited superior fouling resistance to gypsum scaling and combined gypsum-organic fouling, induced by model organic matters like bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA). After applying SA-coating to calibrate the surface properties of the membranes to exclude the influence of surface roughness, hydrophilicity, and functional groups, our study attributed the difference in fouling resistance to variations in ionic selectivity stemming from membrane looseness. Specifically, the primary advantage of looser polyamide NF membranes lies in enhanced Ca2+ permeation, which not only reduces the “egg-box” effect and surface foulant accumulation but also diminishes cake-enhanced concentration polarization, effectively mitigating gypsum-organic fouling. In real water testing scenarios, the enhanced fouling resistance of loose NF membranes was further affirmed. This research underscored the unexpected benefit of loose NF membranes in terms of fouling resistance, providing a novel insight for future application.

A mechanically consistent unified formulation for fluid-porous-structure-contact interaction

Fluid–structure interaction with contact poses profound mathematical and numerical challenges, particularly when considering realistic contact scenarios and the influence of surface roughness. Computationally, contact introduces challenges in altering the fluid domain topology and preserving stress balance. This work introduces a new mathematical framework for a unified continuum description of fluid-porous-structure-contact interaction (FPSCI), leveraging the Navier–Stokes–Brinkman (NSB) equations to incorporate porous effects within the surface asperities in the contact region. Our approach maintains mechanical consistency during contact, circumventing issues associated with contact models and complex interface coupling conditions, allowing for the modeling of tangential creeping flows due to surface roughness. The unified continuum and variational multiscale formulation ensure robustness by enabling stable and unified integration of fluid, porous, and solid sub-problems. Computational efficiency and ease of implementation – key advantages of our approach – are demonstrated by solving two benchmark problems of a falling ball and an idealized heart valve. This research has broad implications for fields reliant on accurate fluid–structure interactions and promising advancements in modeling and numerical simulation techniques.