Two-dimensional Surface Roughness Research Articles

An Experimental Investigation Replicating the Surface Behavior of Ground Steel Gears in Mixed Lubrication Using Twin-Disk Testing Part 1: Running-in

ABSTRACT The surface of ground gear teeth is changed during the initial period of operation through a process termed running-in. During this process asperity peaks are plastically deformed and removed to better distribute the load across the surface, resulting in modification of the surface finish. In this work the influence of pressure, slide-roll ratio, and entrainment velocity on two-dimensional surface roughness parameters is evaluated through the running-in process using a full-factorial experimental programme. Hardened steel disks are used to simulate gear tooth contacts via the use of a twin-disk rig. Results showed that all three variables strongly influence the change in surface geometry, both individually and through both two- and three-factor interactions.

Laser Texturing of Soda Lime Glass Surface for Hydrophobic Surface in Wenzel State

Glass surfaces tend to be hydrophilic when exposed to water resulting in a low water contact angle and high adhesion. Fabrication on a glass surface with low water adhesion can minimize the droplet’s adhesion conduct self-cleaning, and improve the cleanliness of the glass surface. This paper presents surface texturing of the soda-lime glass surface by laser processing three different patterns to improve water contact angle with low water adhesion on the modified glass surface. A design experiment method was developed to determine the effects of laser parameters on the glass surfaces. The laser parameters used are laser power between 0.45 and 1.05W and scanning speeds of 210, 420, and 600 mm/min. The effects of laser parameters on surface morphology, water contact angle measurement, and average surface roughness, Ra were investigated. The characterization was conducted for surface morphology, two-dimensional surface roughness profile, and water contact angle. The results show that the highest water contact angle obtained after laser texturing is up to 125.29° compared to the as-received surface with a contact angle of 32.35°. The highest water contact angle resulted from 420 mm/min scanning speed and 0.45 W of laser power, responding to the surface with a minimum range of Rax and Ray of 0.96 and 1.5 μm. These findings are significant for designing surface modification of self-cleaning glass surface applications like the automotive windscreens, and window panels for high-rise buildings.

Deterministic surface roughness effects on elastic material contact with shear thinning fluid media

Abstract The formation of lubrication films is described using the hydrodynamic lubrication theory, which is based on the Reynolds equation that includes shear thinning behaviors of lubricant. Contacting surfaces are considered to undergo elastic deformation owing to concentrated contact pressures that exceed 1.0 GPa in most engineering applications. Under the contact condition of a high load on a relatively small contact area, elastic deformation of contacting bodies directly influences the formation of the lubricated film. Elastohydrodynamic lubrication (EHL) analysis is applied to correctly analyze the lubricated contact. Under an EHL contact, the scale of the lubrication film thickness is frequently less than that of the surface roughness that results from either the manufacturing or running-in processes. In this work, surface roughness is considered in detail, and two-dimensional surface roughness is measured as that characterizing general engineering surface roughness. The deterministic method regarding the surface roughness is considered for computing EHL film formation under several contact conditions such as load, contact velocity, and elasticity of contacting materials.

Evaluation of Three-Dimensional Surface Roughness in Microgroove Based on Bidimensional Empirical Mode Decomposition.

Micromilling is an extremely important advanced manufacturing technology in the micromanufacturing industry. Compared with the traditional milling process, micromilling has stricter requirements on the surface roughness of the workpiece, and the roughness of the microcurved surface is not easy to measure. In order to more accurately characterize the curved surface morphology of the microgrooves obtained by micromilling, this paper proposes a method to extract the reference plane of the curved surface based on the bidimensional empirical mode decomposition algorithm and characterize the three-dimensional surface roughness of the curved surface. First, we synthesize the morphologies of the microgrooves by simulated non-Gaussian rough surfaces and models of textures. Second, the bidimensional empirical mode decomposition algorithm was used to extract the reference planes of the simulated microgrooves. Third, the three-dimensional roughness parameters suitable for the curved surfaces of microgrooves were selected to establish an evaluation system. The results show that the mean squared errors of the reference planes are below 1%, so bidimensional empirical mode decomposition can effectively extract reference planes, and the evaluation system of three-dimensional surface roughness proposed in this paper reflects morphological characteristics of the curved surfaces of microgrooves more thoroughly than that of two-dimensional surface roughness parameters.

Scattering analyses of arbitrary roughness from 2-D perfectly conductiveperiodic surfaces with moments method

In this paper, a periodic-MoM-based code with high accuracy performance is developed to calculate electromagnetic scattering from a periodic conductive surface in two dimensions with any degree of roughness. Firstly, the existing separate methods in the literature are reviewed step by step to compose a periodic-MoM solution for 2-D periodic surfaces. Then, the dynamic selection of optimal formulation of the periodic-MoM solutions created using these existing methods is evaluated to reduce solution time and obtain high accuracy. In this study, the performance parameters of the existing methods are investigated in solving a real 3-D scattering problem by a periodic-MoM for the first time in the literature. Eventually, a commercial EM solver with a similar numerical approach is employed for comparison, validation, and accuracy achievements of these different periodic-MoM formulations. Furthermore, an analytical solution named Floquet mode-matching method (FMMM) is developed based on the Rayleigh hypothesis for slightly rough surfaces, and the accuracy of the code is tested using this analytical solution. This study is entirely compatible with analytical solutions and gives better results than this commercial EM solver in terms of accuracy. Also, the FMMM formulation derived for comparison provides a more straightforward solution than the small perturbation method (SPM), a classical solution method, and it is adapted to two-dimensional surface roughness for the first time in this paper. However, this full-wave solution has no restriction on surface roughness, unlike the analytical solutions.

Non-contact surface roughness measurement using laser speckle technique

This paper deals with selected contact type stylus method and non-contact type machine vision method using laser speckle for components prepared by grinding of AISI 1040 steel with a variety of wheels and varied depth of cut. In this interactive study, Optical method based on statistical properties of binary images is proposed for machined surfaces. Grounded metal surfaces are used to develop a binary digitized speckle pattern by a beam of He-Ne laser light source. High end camera is used to capture the image of a speckle pattern. White to black pixels ratios is computed from the binary images using image processing toolbox in Matlab. The correlation is developed between white to black pixels ratio and measured two-dimensional surface roughness parameter. Two-dimensional surface roughness parameters are recorded using a contact-type surface profilometer. The results which opted, clearly supports that these parameters have a relationship with a degree of surface roughness. A linear relationship is observed between parameter obtained from proposed technique and measured value of surface roughness using surface profilometer. The statistical analysis represents the performance of maximum relative error in prediction of surface roughness is 9%.

Study on the three-dimensional topography of the machined surface in laser-assisted machining of Si3N4 ceramics under different material removal modes

The surface topography directly impacts the component performance. However, the two-dimensional (2D) surface roughness parameters in the previous studies have been inefficient and inadequate to describe a surface. In this study, with the help of a confocal laser scanning microscope and a scanning electron microscope, the three-dimensional (3D) topography of a machined Si3N4 surface using laser assisted machining (LAM) under different material removal modes was comprehensively characterised and compared using the standard ISO 25178–2:2012 surface texture parameters. The relationship between the 3D topography parameters and service properties was analysed. LAM is effective for machining ceramics with a high hardness and high brittleness. Different material removal modes were obtained by changing the power of the laser and were inferred by comprehensively analysing the macroscopic and microscopic topography of the chips, tool wear, and machined surface. In ductile material removal mode, the surfaces are anisotropic and cutting marks are clearly visible. Decreasing the power of the laser increases the value of the height and functions parameters. Decreasing the power of the laser also decreases the value of the hybrid and feature parameters.

An Analysis of the Surface Geometric Structure and Geometric Accuracy of Cylindrical Gear Teeth Manufactured with the Direct Metal Laser Sintering (DMLS) Method

This paper presents findings concerning the accuracy of the geometry of cylindrical spur gear teeth manufactured with the direct metal laser sintering (DMLS) method. In addition, the results of the evaluation of the tooth surface geometric structure are presented in the form of selected two-dimensional and three-dimensional surface roughness parameters. An analysis of the accuracy of the fabricated gear teeth was performed after gear sand-blasting and gear tooth milling processes. Surface roughness was measured before and after sand-blasting and gear tooth milling. The test gear wheel was manufactured from GP1 high-chromium stainless steel on an EOS M270 machine.

The effect of milling parameters on surface integrity in high-speed milling of ultrahigh strength steel

Ultrahigh strength steel with high specific strength, high thermal strength, good corrosion resistance and other characteristics are widely used in aerospace field. However, these characteristics coupled with its poor thermal conductivity, making it hard to machine, and causes high cutting temperature, serious tool wear can adversely affect the machined surface integrity, ultimately affecting the fatigue performance of the machined part. Therefore, the research on the machined surface integrity of ultrahigh strength steel has very important theoretical significance and engineering application value. The effect of milling parameters on surface integrity in high speed milling of 16Co14Ni10Cr2Mo ultrahigh strength steel is studied. The results show that the influence of milling speed and feed per tooth on two-dimensional and three-dimensional surface roughness is significant, but the milling depth has little effect. Surface roughness increases with milling speed and feed per tooth. The surface residual stresses are in the state of tensile stress, and the surface residual stresses increase with the milling speed, the feed per tooth and the milling depth. The influence of feed per tooth on residual stresses is the most significant. Surface microhardness decreases with milling speed and feed per tooth, but increases with milling depth.

Slip as the basic mechanism for formation of deformation relief structural elements

The experimental results of investigation of the nickel single crystal surface morphology after compression deformation are presented. The quasi-periodic character of the deformation profile, common for shear deformation of different types of relief structural elements, is found. It is demonstrated that the morphological manifestation of these structural elements is determined by local shear systems along octahedral planes. The regularities of the deformation structure in these regions defining the material extrusion and intrusion regions and the specific features of disorientation accumulation are established. If reorientation of local regions takes part in the relief element formation, along with octahedral slip, much stronger growth of the surface area is observed. The possibility of application of two-dimensional and three-dimensional surface roughness parameters for description of deformation relief is considered.

Scale growth of structures in the turbulent boundary layer with a rod-roughened wall

Direct numerical simulation of a turbulent boundary layer over a rod-roughened wall is performed with a long streamwise domain to examine the streamwise-scale growth mechanism of streamwise velocity fluctuating structures in the presence of two-dimensional (2-D) surface roughness. An instantaneous analysis shows that there is a slightly larger population of long structures with a small helix angle (spanwise inclinations relative to streamwise) and a large spanwise width over the rough-wall compared to that over a smooth-wall. Further inspection of time-evolving instantaneous fields clearly exhibits that adjacent long structures combine to form a longer structure through a spanwise merging process over the rough-wall; moreover, spanwise merging for streamwise scale growth is expected to occur frequently over the rough-wall due to the large spanwise scales generated by the 2-D roughness. Finally, we examine the influence of a large width and a small helix angle of the structures over the rough-wall with regard to spatial two-point correlation. The results show that these factors can increase the streamwise coherence of the structures in a statistical sense.

A vehicle-borne and line-structure laser based two-dimensional surface roughness measurement instrument

Surface roughness is the description of surface irregularity and micro topographic randomness. It is an important factor affecting soil microwave radiation. Since both the microwave radiometer and radar detector measure a plane, using 3D data to calculate the 2D surface roughness will get better results. In this paper, we present a line-structure laser based vehicle-borne 2D surface roughness measurement instrument which can measure a much bigger size and thus bring higher accuracy and greater capability. Meanwhile, the portability is not affected since it is carried around by a vehicle. The precision test and field test showed that the maximum average relative error is only 1.3%. We also implemented a graphics processing unit version of the data processing program, which reduced the runtime to 540 seconds from 45,393 seconds on central processing unit.

Two-dimensional evaluation of 3D needled Cf/SiC composite fiber bundle surface

The variations of fiber bundle surface microstructure have direct influence on the material performance, especially the friction and wear properties. Therefore, fiber bundle is the smallest evaluation unit of Cf/SiC composite surface. However, due to the anisotropy and inhomogeneity of Cf/SiC composite, it is difficult to evaluate the surface characteristics. Researchers think that two-dimensional evaluation is not suitable for the composites surface assessment any more because of its complex composition and varied surface structure. In this paper, a novel method is introduced for the evaluation of 3D needled Cf/SiC composite fiber bundle surface. On the level of Cf/SiC composite fiber bundle surface, two-dimensional evaluation method is adopted, with which the fiber bundle surface quality can be quantitatively evaluated by the two-dimensional surface roughness Ra. As long as the extracted surface profiles averagely distributed on Cf/SiC composite fiber bundle surface, with appropriate sampling length and sampling number, the mean value of Ra can estimate the whole surface roughness, thus reflecting the roughness degree of surface accurately. This study not only benefits the detection of 3D needled Cf/SiC composite fiber bundle surface quality, and lays a foundation on the evaluation of material functional features in further. And it corresponds to the convenient application in engineering practice.

Unveiling the mechanisms of dressed-photon–phonon etching based on hierarchical surface roughness measure

Dressed-photon–phonon (DPP) etching is a disruptive technology in planarizing material surfaces because it completely eliminates mechanical contact processes. However, adequate metrics for evaluating the surface roughness and the underlying physical mechanisms are still not well understood. Here, we propose a two-dimensional hierarchical surface roughness measure, inspired by the Allan variance, that represents the effectiveness of DPP etching while conserving the original two-dimensional surface topology. Also, we build a simple physical model of DPP etching that agrees well with the experimental observations, which clearly shows the involvement of the intrinsic hierarchical properties of dressed photons, or optical near-fields, in the surface processing.

Comparisons of microcellular polylactic acid parts injection molded with supercritical nitrogen and expandable thermoplastic microspheres: Surface roughness, tensile properties, and morphology

Microcellular injection molding is capable of fabricating light weight, dimensionally stable plastic parts while using less material and energy. Two kinds of blowing agents, namely, supercritical nitrogen and expandable thermoplastic microspheres, were employed to produce foamed polylactic acid parts. The surface characteristics were evaluated with a two-dimensional surface roughness analyzer and a three-dimensional white-light interferometer surface profiler. Through surface roughness comparisons, injection molded American Society for Testing Material tensile test bars with expandable thermoplastic microspheres exhibited better surface quality than their supercritical nitrogen counterparts. The tensile properties of injection molded polylactic acid tensile bars with nitrogen and expandable thermoplastic microspheres at various weight concentrations were investigated. The results showed that the polylactic acid/nitrogen parts possessed a better Young’s modulus and tensile strength. The microstructure on the fractured cross-sectional surfaces was characterized using a scanning electron microscope. As reflected by the testing results, the cell microstructure – such as cell size and cell density, and multi-layered structure with a foamed core sandwiched by skin layers – played an important role in the surface quality and mechanical properties. In addition, while an appropriate expandable thermoplastic microspheres content had a positive effect on the cell microstructure and weight reduction, too high of a concentration of expandable thermoplastic microspheres adversely affected the tensile properties and surface roughness of the microcellular polylactic acid tensile test bars.

About turbulence statistics in the outer part of a boundary layer developing over two-dimensional surface roughness

The influence of surface roughness on a high Reynolds number turbulent boundary layer is investigated in the light of Townsend's wall similarity hypothesis. There is conflicting information in the literature about the effect of surface roughness on the flow structure in the outer layer. Flows over roughness consisting of spanwise rods appear to show unusually strong interaction between the wall and the wake region. It has been suggested that flows which show strong modifications in the outer layer suffer from lack of scale separation between the roughness scale and the largest scale given by the boundary layer thickness. One of the flows which have documented significant roughness effects across the entire layer is the boundary layer developing over roughness made up of spanwise aligned square bars. Here we compare one such flow taken at relatively low Reynolds number with measurements for a boundary layer which develops at much higher Reynolds number. The high Reynolds number (Reθ = 32 600) assures that the range of scale is wide, while at the same time the size of the roughness elements is sufficiently large for the flow to be fully rough. Both sets of data are compared to a smooth wall reference boundary layer and from probability distributions, the quadrant contributions to the shear stress and triple correlation profiles, we show that the outer layer changes are significantly reduced when increasing the Reynolds number and thereby the range of scales. In this case the wall perturbation of the flow is shown to be much smaller than reported in other experiments using the same geometry. Here we find that the modifications in the turbulent structure are limited to about five times the roughness scale. This is in accordance with the wall similarity hypothesis.

A Study on how Grinding Technology Parameters Affect the Surface Texture Formation of Marine Diesel Engine Crankshafts

New technology has been developed to permit repair work on one of the main and most important components of shipboard diesel engines—the crankshaft—without removing it from engine. It is no longer necessary to dismantle the whole engine and as such, this innovative technology significantly reduces repair costs. However, the impact of this novel grinding technology on the surface roughness parameters is not yet clear and requires additional scientific analysis. Machining technology and cutting regimes, as well as the material of the tool being used, all have a direct impact on the surface texture and consequently on the quality of the repair as a whole. Therefore, to realise this innovation, it is necessary to carry out additional research into the impact of grinding technology parameters on the surface formation of the crankshaft main and crankpin bearings (journals). Current roughness research is usually restricted to two-dimensional surface roughness parameters—simple profile analysis. Nevertheless, in practice any surface has three dimensions, which give it a characteristic texture. It is therefore also necessary to create a new theoretical 3-D surface model for crankshaft bearings surfaces. This will allow us to analyse the full-scale impact of technological grinding regimes on the actual three-dimensional surface. This study revealed that optimal 3-D surface roughness (texture) parameters for crankshafts depend upon: the mean arithmetical deviation of the surface, RaT, and two perpendicular surface spacing parameters between the peaks Sm1 and Sm2. Multifactorial research shows individual significance of each technological regime and overall impact on the 3-D parameter RaT, Sm1 and Sm2. The approach and methodology adopted for the experiments enabled us to identify the optimal and most appropriate grinding technology parameters.

Effects of irregular two-dimensional and three-dimensional surface roughness in turbulent channel flows

Wall-resolved Large Eddy Simulation of fully developed turbulent channel flows over two different rough surfaces is performed to investigate on the effects of irregular 2D and 3D roughness on the turbulence. The two geometries are obtained through the superimposition of sinusoidal functions having random amplitudes and different wave lengths. In the 2D configuration the irregular shape in the longitudinal direction is replicated in the transverse one, while in the 3D case the sinusoidal functions are generated both in streamwise and spanwise directions. Both channel walls are roughened in such a way as to obtain surfaces with statistically equivalent roughness height, but different shapes. In order to compare the turbulence properties over the two rough walls and to analyse the differences with a smooth wall, the simulations are performed at the same Reynolds number Reτ=395. The same mean roughness height h=0.05δ (δ the half channel height) is used for the rough walls.The roughness function obtained with the 3D roughness is larger than in the 2D case, although the two walls share the same mean height. Thus, the considered irregular 3D roughness is more effective in reducing the flow velocity with respect to the 2D roughness, coherently with the literature results that identified a clear dependence of the roughness function on the effective slope (see Napoli et al. (2008)), higher in the generated 3D rough wall. The analysis of higher-order statistics shows that the effects of the roughness, independently on its two- or three-dimensional shape, are mainly confined in the inner region, supporting the Townsend’s wall similarity hypothesis. The tendency towards the isotropization is investigated through the ratio between the resolved Reynolds stress components, putting in light that the 3D irregular rough wall induces an higher reduction of the anisotropy, with respect to the 2D case.

A Lubrication Equation Incorporating Two-Dimensional Roughness Effects, With Emphasis on the Patterned Data Islands of a Recording Disk

Current industrial applications require a consideration of two-dimensional surface roughness effects in design and optimization of fluid bearings. Although the influence of striated surface roughness on fluid lubrication is now at a fairly mature level of understanding, the knowledge and understanding of two-dimensional roughness effects is not nearly at the same level as that achieved over the past several decades for one-dimensional striations. The subject of this paper includes the formulation of a practical “roughness averaged” lubrication equation that is appropriate for two-dimensional surface roughness and applicable over a wide range of Knudsen numbers. After derivation by multiple-scale analysis, the resulting lubrication equation is specialized to treat the patterned data islands located on a storage medium as a two-dimensional roughness pattern, and then used to determine the effect of this roughness on the air-bearing interface between recording head slider and disk. The roughness averaged lubrication equation is solved numerically by a variable-grid finite-difference algorithm, and computed results are included for several bearing geometries.

Study on evaluation of RB-SiC aspherical mirror high frequency surface quality fabricated with fixed abrasive technology

The issue of the letter is focused on the RB-SiC aspherical mirror high frequency surface quality which is fabricated with the different type fixed abrasive pellets. The two-dimensional (2D) surface roughness of the mirror is simulated and experimented. The errors between the simulation and the experiment are 5.97%, 3.19%, 3.59%, 37.37% using W1.5, W3.5, W5, W7 pellets respectively. The error emerging reason is analyzed in detail after the comparison. Also the fractal theory is applied on the analysis of the optical mirror surface fabricated with the fixed abrasive technology. The analysis result shows that the good surface quality of the RB-SiC mirror can be obtained quickly with being polished with the fixed abrasive technology. So the fixed abrasive technology is very suitable for the fast optical surfacing, especially can obtain good surface roughness fast in the stage of grinding mirror which is not suitable for being tested with interferometer. OCIS codes: 220.0220, 220.4000, 220.4610, 220.5450. doi: 10.3788/COL201210.S22201. Generally, the surface error, the ripple and the surface roughness should be tested quantificationally when a SiC mirror is finished. The mirror surface quality is evaluated through the parameters tested. The surface error which is also called low frequency error is studied for decades [1 3] . So the surface error is not in the letter’s extension, it is focused on the high frequency error of the SiC mirror fabricated with the fixed abrasive technology, which is studied through several different methods. The existence of the high frequency error on the mirror will increase the scattering energy, decreasing the effective energy entering the camera, then the image quality will be decreased. So we should understand exactly what factor and which stage leads to the increase of the high frequency error on the mirror in the fabrication. In the most situation, the study is only focused on the method of testing the high frequency error, but the theoretical study on the high frequency error is seldom. The starting point of the letter is simulating the microcosmic formation the high frequency error in the fabrication process. And also the mirror surface fabricated with pellets is analyzed and evaluated using the fractal theory for the first time. Because of the complexity of simulating the fabrication process of SiC mirror with diamond abrasive actually, the following important assumption is made: the final mirror surface is formed by the indentation into the SiC mirror with the still diamond particles. In the fabrication of the SiC material, the size and depth of the indentation formed by the diamond particles are totally different. So we are on the assumption that the position distribution of the indentations is uniform, the size of the indentations are in Gaussian distribution, the depth is � [4]