Effect Of Surface Roughness Research Articles

INFLUENCE OF SUBSTRATE SURFACE ROUGHNESS ON PUSH-OFF STRENGTH FOR FRICTION SURFACING OF LOW CARBON STEEL WITH AA6061-T6 ALUMINIUM ALLOY

Surface roughness plays an essential role in friction surfacing deposition as a smooth substrate surface polishes both consumable and substrate tools, resulting in a lack of deposition. Hence, an attempt is made to investigate the effect of substrate surface roughness while friction surfacing of AA6061-T6 coating on CR01 low carbon steel and its performance is compared through push-off strength. It is revealed that with an increase in substrate surface roughness, more rubbing action occurs between consumable tool and substrate, which results in higher heat generation and reduction in deposition thickness. The grain refinement is observed at the coating region due to dynamic recrystallisation, which results in fine grain microstructure. The substrate with Ra roughness values 1.5-2.5, 5.5-6.5 and 7.5-8.5 µm showed 26, 32 and 45 MPa push-off strength, respectively. Hence, it is inferred that the push-off strength increases substantially with an increase in the substrate surface roughness.

Performance analysis of tilting pad thrust bearing incorporating the surface roughness, texture and turbulence effect

In order to improve the lubrication performance of the friction pair, the effect of composite micro-texture on the lubrication performance of the tilting pad thrust bearing is studied. Based on the structural model of tilting pad thrust bearing considering composite micro-texture, the lubrication characteristics of thrust bearing with composite micro-texture parameters and tilting pad parameters are analyzed. At the same time, the theoretical model of tilting pad composite micro-texture bearing considering roughness and turbulence effect is established, and the performance of thrust bearing considering roughness and turbulence effect is studied. The results show that the performance of composite micro-textured bearings is better than that of single micro-textured bearings, the performance of tilting pad bearings is better than that of parallel pad bearings, and the performance of circular composite fish-shaped micro-textured tilting pad bearings is the best. The optimal bearing fulcrum position is near the inner diameter, and the optimal fulcrum circumferential inclination angle is about 27.5°. Considering the roughness and turbulence effect, the maximum pressure and bearing capacity of the bearing improves, and the friction coefficient significantly reduces.

A computational investigation of electron transport in defected Cu thin films

Interconnects are a key component of integrated circuits (IC) and play a major role in the speed and power consumption of an IC. While surface roughness is essential for ensuring adhesion to other components in an IC, it also increases electron scattering at the surface, which can dramatically increase resistivity. Barrier layers have been introduced to mitigate the effect of rough Cu surfaces, but explanations of their behavior are varied. Using a combination of density functional theory (DFT) and the non-equilibrium Green’s function technique in conjunction with DFT (NEGF-DFT), our work aims to identify key tradeoffs between surface roughness profiles and electronic performance in copper wire interconnects, and how barrier layer atoms affect conductance across the Cu surface. We find that by removing atoms from the surface, the current allowed across the film is reduced to that of a thinner pristine film, but that as the voltage is increased the defected film recovers some of the conductance of the pristine system. By replacing the vacancy with a substituent atom (Ag, Al, Au, Co, Ir, Ni, Pd, Rh, Sn, Zn, Zr) we find that conductance across the film is intimately related to the periodic table group of the substituent atom relative to Cu.

Performance of rough secant slider bearing lubricated with couple stress fluid in the presence of magnetic field

The effect of surface roughness, magnetic field, and couple stress on the performance of secant slider bearing is studied in this paper. The effectiveness of the bearing is assessed by using a couple stress liquid as the lubricant in the process. Because of microstructural impacts, couple stress fluids have distinctive rheological characteristics. These features have the potential to make a major impact on the bearing’s performance. The novel aspect of this study is that the roughness of the secant slider is taken into consideration. The modified Reynolds equation is derived using Christensen’s stochastic theory for roughness. Here, both transverse and longitudinal roughness patterns are considered. The analytical solutions are obtained for steady-state pressure, load-carrying capacity, film stiffness, and damping coefficient. The results are presented for various parameters through graphs and tables. The combined effect of the magnetic field and couple stress is significant on bearing characteristics. It is noticed that the bearing features increase with the longitudinal roughness parameter, and the reverse phenomenon is observed with the transverse roughness parameter. When a transverse roughness pattern is assumed on a secant slider bearing, characteristics like pressure, load, stiffness of the film, and damping coefficient increase significantly.

Surface nanoroughness impacts the formation and stability of supported lipid bilayers

Solid supported lipid bilayers (SLBs) are excellent platforms for studying the biophysical properties of cell membranes, as well as versatile biomimetic films for biotechnology applications. Among the existing approaches used to form SLBs, vesicle fusion and rupture onto solid supports is the most commonly employed one owing to its straightforward procedure. SLBs are typically formed on atomically flat and very hydrophilic surfaces, overlooking the influence of roughness and topography on membrane formation and organization. As a matter of fact, lipid bilayers in vivo are corrugated at the nanoscale level, as a result of interactions with proteins, fibrils, and other components within the intracellular and extracellular environment. Fundamental studies of the effect of surface roughness on SLBs are scarce and restricted to few contributions, where nanoroughness has shown to affect lipid mobility by a 5-fold decrease and inhibit domain growth in phase-separated membranes. In this work, the impact of nanoroughness on the formation and stability of SLBs onto SiO2 surfaces with different degrees of vertical and lateral surface roughness is studied. Combining quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy with force spectroscopy (AFM-FS), it is shown that nanoroughness affects the formation of SLBs by increasing the activation energy of vesicle fusion, rupture and spreading, and weakens the stability and lateral organization of the formed SLBs.

Direct Numerical Simulation of Transitional and Turbulent Flows Over Multi-Scale Surface Roughness—Part I: Methodology and Challenges

Abstract High-fidelity simulation of transitional and turbulent flows over multi-scale surface roughness presents several challenges. For instance, the complex and irregular geometrical nature of surface roughness makes it impractical to employ conforming structured grids, commonly adopted in large-scale numerical simulations due to their high computational efficiency. One possible solution to overcome this problem is offered by immersed boundary methods, which allow wall boundary conditions to be enforced on grids that do not conform to the geometry of the solid boundary. To this end, a three-dimensional, second-order accurate boundary data immersion method (BDIM) is adopted. A novel mapping algorithm that can be applied to general three-dimensional surfaces is presented, together with a newly developed data-capturing methodology to extract and analyze on-surface flow quantities of interest. A rigorous procedure to compute gradient quantities such as the wall shear stress and the heat flux on complex non-conforming geometries is also introduced. The new framework is validated by performing a direct numerical simulation (DNS) of fully developed turbulent channel flow over sinusoidal egg-carton roughness in a minimal-span domain. For this canonical case, the averaged streamwise velocity profiles are compared against results from the literature obtained with a body-fitted grid. General guidelines on the BDIM resolution requirements for multi-scale roughness simulation are given. Momentum and energy balance methods are used to validate the calculation of the overall skin friction and heat transfer at the wall. The BDIM is then employed to investigate the effect of irregular homogeneous surface roughness on the performance of an LS-89 high-pressure turbine blade at engine-relevant conditions using DNS. This is the first application of the BDIM to realize multi-scale roughness for transitional flow in transonic conditions in the context of high-pressure turbines. The methodology adopted to generate the desired roughness distribution and to apply it to the reference blade geometry is introduced. The results are compared to the case of an equivalent smooth blade.

Investigating a method for macroscale energy extraction from random electrons movement

This paper aims to investigate a novel method for regularizing the random movements of electrons, in order to generate net movement and extract energy from the resulting electromotive force. The proposed method involves designing anisotropic conditions, focusing on exploring the effects of surface roughness on a metal wire in a two-dimensional space with the presence of a magnetic field. This paper presents a mathematical model for studying the proposed method. Furthermore, simulation results are analyzed and discussed in the context of the proposed method. By investigating the effects of surface roughness on electrons movement and voltage generation, this paper aims to contribute to the development of new methods for energy extraction from random electrons movement.

High performance computation of a lagrangian approach for turbulent flow investigations around cylinders with different surfaces

The Discrete Vortex Method finds application in engineering contexts, primarily for the estimation of hydrodynamic forces in fluid-structure interaction within a two-dimensional domain. In recent years, this method has been extended with solutions that incorporate turbulence and rough surface effects. This paper reports advancements resulting from parallel programming using OpenMP, enabling the implementation of Lagrangian methods that were previously computationally intensive. Additionally, partial results of investigations into the control of vortex shedding by changing the roughness of the body are also presented.

Sliding motion of highly deformed droplets on smooth and rough surfaces: Shape oscillation, chaotic breakage, corner shape, and pearling

The sliding behavior of droplets on smooth and rough surfaces with various surface wettabilities is investigated by many-body dissipative particle dynamics simulations. On a smooth surface, as the driving force (Bo) increases, the droplet shape and velocity (Cac) before breakage can be classified into four distinct regimes: (I) nearly spherical cap with Cac∝Bo; (II) oval shape with negative deviation from the linear relation; (III) elongated shape without a neck, where Cac decreases with increasing Bo; and (IV) oscillation of an elongated shape with fluctuating sliding velocity. On rough surfaces, corner-shaped droplets, which are absent on a smooth surface, can be observed. A further increase in Bo leads to the formation of cusp and pearling. Different from pinching-off on rough surfaces, which produces a cascade of smaller droplets through groove-induced shedding, chaotic breakage of a droplet on a smooth surface is caused by an unsteady flow field. Finally, a universal linear relationship between the sliding velocity based on the surface velocity (Cas) and the modified driving force (Bo**) is derived to take into account the effects of surface wettability and roughness.

The bending-torsional vibration characteristics of gear transmission under the effect of tooth surface roughness

The bending-torsional vibration characteristics of gear transmission under the effect of tooth surface roughness

A Comprehensive Study on the Effects of Surface Roughness on Power Consumption and Heat Transfer Performance in Novel In-Tube Condensation r123yf Refrigerant Systems

This study investigates the impact of surface roughness on the condensation Heat Transfer Coefficient (HTC) of R123yf refrigerant in a uniquely designed test rig with pre-condenser and post-condenser for quality regulation. In mining industries, the mining equipment consumes more amount to power for the Air Conditioning system. To reduce the power consumption of copper metal inside the surface morphology needs to be changed. Experiments were conducted in a 750 mm long, 8.4 mm internal diameter copper tube, with regard to mass flux varying from 150 kg.m-2.s-1 to 300 kg.m-2.s-1, refrigerant quality varying from 0.3 to 0.8, and saturated temperature from 35°C to 45°C. The impact of varying surface roughness (1.5 μm, 2.5μm, 3.4 μm, and 6.7 μm) on HTC was examined. The plane tube condensation experimental results agreed with M M Shah's heat transfer coefficient correlations, with a 20% absolute mean deviation. It was observed that increasing surface roughness enhanced the HTC. The optimal surface roughness was determined to be 3.4 μm, as it resulted in a significant increase in HTC (26.25%) with a moderate rise in power consumption (15.40%). Higher surface roughness led to a drastic increase in power consumption, making it less desirable for practical applications. Through a systematic analysis of the experimental data, this study identifies the critical trade-off between surface roughness and power consumption, providing guidance for the design of energy-efficient condensation heat transfer systems using R123yf refrigerant. By pinpointing an optimal surface roughness for copper tubes used in refrigeration, this study offers a pragmatic solution for enhancing the efficiency of air conditioning systems in mining equipment, a sector notorious for high energy expenditures. The findings indicate a direct application in mining operations where equipment cooling demands contribute significantly to energy consumption. Implementing the recommended surface modifications can lead to substantial energy savings, thereby reducing operational costs and improving the sustainability of mining activities. Furthermore, the adaptation of R123yf refrigerant systems with optimized surface roughness could serve as a model for energy conservation measures across various facets of the mining industry..

The effect of thickness and surface roughness on the absorption coefficient (α) of Aluminum (Al)

Noise is an essential factor in determining various interior elements and machinery, especially those made of metal. The noise level generated by metal is caused by the low level of sound attenuation factor, known as the absorption coefficient (alpha, α) of the metal. Aluminum (Al) metal has the characteristics of corrosion resistance, lightweight, attractive color, and ease of form, so it is popular as a material for various households, machinery, and industrial machinery. This study explains the effect of surface roughness (0.05, 0.12, and 0.15 Ra) and thickness (2, 4, and 6 mm) of Al specimens on the measurement values of absorption coefficient (α). The measurements result show that the average value of α is relatively stable by variations in surface roughness and thickness within the low to medium frequency range (200-800 Hz). Although in general there are increased α values for the high-frequency ranges (1000-1200 Hz), the lowest average of α value occurs in the specimen with the highest surface roughness of Ra 25. Thus, even though the variation in thickness has no significant effect on the α value, the higher surface roughness of Al will reduce the value of the absorption coefficient (α) resulting in higher noise generated.

Study of calcium carbonate scaling on steel using a high salinity brine simulating a pre-salt produced water

In Brazilian pre-salt production, high carbon dioxide (CO2) levels in the associated gas, high salinity in the water, and high levels of calcium ions cause problems related to corrosion and scale. In practice, the scaling process already begins in the formation and near the wellbore region. However, this work has addressed this issue only on a steel surface, representing what can occur in oil production tubings and equipment since the build-up of these products in the internal walls can also impact the production flow guarantee. Parameters related to the substrate and the environment can influence calcium carbonate (CaCO3) precipitation mechanisms. In this study, the effect of steel surface roughness on calcium carbonate scaling experiments has been studied in a high salinity brine containing sodium bicarbonate (NaHCO3) and calcium chloride (CaCl2), simulating pre-salt produced water and under flow conditions. The scaling tests were carried out with a set-up composed of a peristaltic pump to recirculate the test solution through a flow cell. The scale build-up was analysed by using techniques such as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersion X-ray Spectroscopy (EDS). For tests carried out in 3 h, the smoother surfaces had lower adhesion of calcium carbonate than surfaces with higher roughness. Lepidocrocite and rokuehnite, which are corrosion products, were formed in the substrates with higher roughness values, promoting aragonite formation. This work demonstrates that roughness influences calcium carbonate scale formation under flow conditions, besides affecting the calcium carbonate polymorphs associated with the corrosion process.

Uncovering the Effect of Physical Conditions and Surface Roughness on the Maximum Spreading Factor of Impinging Droplets Using a Supervised Artificial Neural Network Model

Uncovering the Effect of Physical Conditions and Surface Roughness on the Maximum Spreading Factor of Impinging Droplets Using a Supervised Artificial Neural Network Model

Fatigue Life and Impact Toughness of PBF-LB Manufactured Ti6Al4V and the Effect of Heat Treatment

While additive manufacturing of metals has been rapidly growing industry for the past decade, the quality and the fatigue properties of the materials are still not very well known. In this study, we focus on the laser powder bed fusion (PBF-LB) manufactured Ti6Al4V. The as built material was compared to the heat treated counterpart by microstructural analysis, and the mechanical properties, impact toughness and the fatigue strength were determined. Bending fatigue testing was conducted for both as built and polished material to reveal the effect of surface roughness. The results showed that the heat treatment and the resulting microstructural change is crucial for the material properties and the material showed very brittle behaviour without it. According to the results, the surface quality plays also an important role in the fatigue life of the material, especially if no heat treatment is used.

Surface Roughness Effects on Magnetic Properties and Switching Mechanism in Iron Nanowires

Nanowires fabricated with experimental techniques are never perfect and possess structural imperfections. The effect of the resulting surface roughness on magnetic properties of iron nanowires has been simulated here with the use of numerical technique involving atomistic-resolved software Vampire. A two-regime or a power-law decrease in the coercive field has been found for the roughness amplitude up to 30% of the perfect radius of the wire. The roughness of the surface of the side face of cylindrical wire makes the ends of the cylinder inequivalent as far as the switching mechanism is concerned. As a result, the switching becomes dominated by a transverse domain wall arising at one specific end only. Both the coercive field and the switching mechanism are essential in designing magnetic devices, e.g., for memory storage.

Numerical investigate of the effects of surface roughness on local scour around pipeline under steady current condition

A two-dimensional numerical model was developed to investigate the effects of the surface roughness on local scour around pipeline based on Naiver-Stokes equations. Both suspended load and bedload transport are considered for the sand motion equation. Present numerical model is verified accurately for simulating local scour around pipeline. The numerical results show that the surface roughness has a significant effect on the process of local scour, i.e. forces, Shields parameter and scour depth. For rough pipeline, the average value of the drag force coefficient on the pipeline, the RMS value of the lift coefficient, the scour depth and the scour width all decrease rapidly with increasing roughness and then change slowly.

The influence of surface roughness on postcritical flow over circular cylinders revisited

This work investigates the effect of surface roughness on cylinder flows in the postcritical regime and reexamines whether the roughness Reynolds number ( $Re_{k_s}$ ) primarily governs the aerodynamic behaviour. It has been motivated by limitations of many previous investigations, containing occasionally contradictory findings. In particular, many past studies were conducted with relatively high blockage ratios and low cylinder aspect ratios. Both of these factors appear to have non-negligible effects on flow behaviour, and particularly fluctuating quantities such as the standard deviation of the lift coefficient. This study employs a 5 % blockage ratio and a span-to-diameter ratio of 10. Cylinders of different relative surface roughness ratios ( $k_s/D$ ), ranging from $1.1\times 10^{-3}$ to $3\times 10^{-3}$ , were investigated at Reynolds numbers up to $6.8 \times 10^5$ and $Re_{k_s}$ up to 2200. It is found that the base pressure coefficient, drag coefficient, Strouhal number, spanwise correlation length of lift and the standard deviation of the lift coefficient are well described by $Re_{k_s}$ in postcritical flows. However, roughness does have an effect on the minimum surface pressure coefficient (near separation) that does not collapse with $Re_{k_s}$ . The universal Strouhal number proposed by Bearman (Annu. Rev. Fluid Mech., vol. 16, 1984, pp. 195–222) appears to be nearly constant over the range of $Re_{k_s}$ studied, spanning the subcritical through postcritical regimes. Frequencies in the separating shear layers are found to be an order of magnitude lower than the power law predictions for separating shear layers of smooth cylinders.

The roles of surface temperature and roughness in droplet splashing

In this work, the effects of surface temperature and surface roughness on the splashing phenomena of droplet impact are experimentally investigated. The transition temperature, TTr, from the deposition regime to the rebound regime is determined on various rough surfaces. It is found that TTr decreases with increasing surface roughness. Furthermore, the critical splash number, Kc, above which droplet splash takes place, exhibits distinct dependences on the surface temperature when the surface temperature is increased across the transition temperature. Below TTr, Kc increases as the surface temperature is raised, and the increasing rate decreases as the surface roughness is increased. Above TTr, however, Kc decreases abruptly and becomes insensitive to both surface roughness and temperature. Theoretical analysis is carried out to elucidate the observations. The results in this work provide useful information for diverse industrial processes involving droplet splashing phenomena.

Effect of roughness, contact pressure and lubrication on the onset of galling of the 6082 aluminium alloy in cold forming, a numerical approach

The effect of surface roughness, contact pressure and lubrication on the onset of galling of aluminum 6082-T6 is studied with a pin-on-plate tribometer. The design of experiments involves pins with mean arithmetic roughness Ra equaled to 0.2, 0.35 and 0.6 μm, normal loads ranging from 5 to 600 N, and 4 different lubrications: without lubricant, with MoS2 dry lubricant, with pure mineral oil and with a highly chlorinated paraffin oil. Tests are performed at room temperature and are repeated three times. Experimental results show the great sensitivity of the onset of galling to the roughness and the beneficial effect of dry and liquid lubricants. The occurrence of galling is study by optical micrographs, by the analyses of the coefficient of friction, and by the use of finite element simulations. It comes that the variation of the coefficient of friction is not self-sufficient to detect the onset of galling. The finite element computations involves Wilson’s lubrication model and Xue’s damage model. Galling is assumed when finite elements near the contact area reach the critical damage Dc. This numerical approach leads to a good prediction of the onset of galling for the tests performed under constant normal load. For tests performed with increasing normal loads and various lubricants, the numerical prediction overestimate the sliding length before galling occurs.