Standard Roughness Parameters Research Articles

Criteria for Evaluating the Tribological Effectiveness of 3D Roughness on Friction Surfaces

A new technique for finishing the surfaces of friction pairs has been proposed, which, in combination with the original test method, has shown a significant influence of the initial roughness configuration (surface texture) on friction and wear. Two types of finishing processing of the shaft friction surfaces were compared, and it was found that the friction and wear coefficients differ by more than 2–5 and 2–4 times, respectively. Based on a new methodology for analyzing standard roughness parameters, the tribological efficiency criteria (in the sense of reducing friction and wear) are proposed for the initial state of the friction surface of a radial plane sliding bearing shaft relative to the friction direction, which is consistent with its frictional characteristics. Comparison of the laboratory test results with the surface tribological efficiency criteria showed that these criteria are very promising for controlling existing technologies and optimizing new technologies for friction surface finishing in various friction systems.

Characterization of Micro-Threaded Stem Taper Surfaces of Cementless Hip Endoprostheses.

We investigated micro-threaded stem taper surface and its impact on premature failures, aseptic loosening, and infection in cementless hip endoprostheses. Our study focused on the fretting, and crevice corrosion of micro-threaded tapers, as well as the characterization of the microstructure and surface properties of two new and three retrieved Zweymüller stem tapers. The retrieved samples were selected and examined based on the head-stem taper interface being the sole source of modularity with a metallic component, specifically between the Ti alloy taper stem and the ceramic head. To determine the surface chemistry and microstructures of both new and retrieved hip endoprostheses stem taper titanium alloy, scanning -electron microscopy (SEM) was employed for morphological and microstructural analyses. Energy dispersive spectroscopy (EDS) was utilized for characterizing chemical element distribution, and electron backscattered diffraction (EBSD) was used for phase analysis. The roughness of the micro-threated stem tapers from different manufacturers was investigated using an optical profilometer, with standard roughness parameters Ra (average surface roughness) and Rz (mean peak to valley height of the roughness profile) being measured. Electrochemical studies revealed no fretting corrosion in retrieved stem tapers with ceramic heads. Consequently, three retrieved tapers and two new ones for comparison underwent potentiodynamic measurements in Hank's solution to determine the corrosion rate of new and retrieved stem taper surfaces. The results showed a low corrosion rate for both new and prematurely failed retrieved samples due to aseptic loosening. However, the corrosion rate was higher in infected and low-grade infected tapers. In conclusion, our study suggests that using ceramic heads reduces taper corrosion and subsequently decreases the incidence of premature failures in total hip arthroplasty.

Adapting Shot Peening for Surface Texturing Using Customized Additive Manufactured Shots

Surface textures in engineering materials not only affect the reflective properties and aesthetics but if properly designed can modulate surface‐related properties such as wettability, fatigue, wear, corrosion, and scratch resistance. Herein, a new surface texturing method is introduced based on the conventional shot peening process. Custom shots are designed, and their surface texturing capability is investigated on acrylonitrile butadiene styrene (ABS) polymer substrates. A finite‐element model is developed to bombard the substrate using AISI 316 stainless steel customized shots. The generated unique textures are compared qualitatively by visual examination and quantitatively using the standard surface roughness parameters. As a proof of concept, preliminary experiments are performed using a candidate custom shot and a spherical shot to treat the ABS sheets. The results highlight the high potential of the shot peening technique paired with additive manufacturing for customizing the peening media to be used for surface texturing polymeric materials.

Quantification of Mesoscale Deformation-Induced Surface Roughness in α-Titanium

The phenomenon of mesoscale deformation-induced surface roughening in titanium polycrystals is examined experimentally and numerically. The evolution of the surface morphology under uniaxial tension is analyzed in terms of the standard and ad hoc roughness parameters and the fractal dimension. The statistical estimates are compared to the grain-scale stress-strain fields in order to reveal an interrelation between the in-plane plastic strains and out-of-plane surface displacements. A strong correlation with a determination coefficient of 0.99 is revealed between the dimensionless roughness parameter Rd and the corresponding in-plane plastic strain. The standard roughness parameters Ra and RRMS are shown to correlate linearly with the in-plane strains, but only for moderate tensile deformation, which is due to filtering out low-frequency components in the surface profiles. The fractal dimension DF changes with the subsection strains in a sawtooth fashion, with an abrupt drop in the neck region. The descent portions of the DF dependences are supposedly related to the appearance of low-frequency components in the structure of the surface profiles.

A Surface Skewness and Kurtosis Integrated Stress Concentration Factor Model

Abstract Surface skewness and kurtosis are two crucial topography property indexes that greatly influence the functional performance of the machined surface. This paper proposes a modified model of stress concentration factor (SCF), which integrates these two surface texture parameters with the well-known standard surface roughness parameters (Arola's model). The relative weight of positive and negative heights of the surface is considered to describe the influence of the shape of the peaks and valleys on the stress concentration of the surface profile for the first time, meanwhile, without losing the effect of the standard surface roughness parameters. The performance of the modified model is studied by comparing it with the other two models involving various aspects of the functional performance of machined surfaces, including fatigue life, wear resistance, fretting crack nucleation, and initiation behaviors, as well as the surface bearing capability. The results indicate that by accounting for the surface skewness and kurtosis parameters, the modified model is more suitable for evaluating the SCF of machined surfaces, appropriately describing the correlation between surface texture and fatigue life and achieving a good prediction of fatigue life compared with the experimental results.

Nanotopography Evaluation of NiTi Alloy Exposed to Artificial Saliva and Different Mouthwashes.

Nitinol (NiTi) alloy is a widely used material for the production of orthodontic archwires. Its corrosion behavior in conditions that exist in the oral cavity still remains a great characterization challenge. The motivation behind this work is to reveal the influence of commercially available mouthwashes on NiTi orthodontic archwires by performing non-electrochemical corrosion tests and quantifying the changes in the nanotopography of commercially available NiTi orthodontic wires. In this study, we examined the behavior of NiTi alloy archwires exposed for 21.5 days to different corrosive media: artificial saliva, Eludril®, Aquafresh®, and Listerine®. The corrosion was characterized by contact mode atomic force microscopy (AFM) before and after the corrosion tests. A novel analysis methodology was developed to obtain insight into locations of material gain or material loss based on standard surface roughness parameters Sa, Sdr, Ssk, and S10z. The developed methodology revealed that fluoride-containing mouthwashes (Aquafresh® and Listerine®) dominantly cause material loss, while chloride-containing mouthwash (Eludril®) can cause both material loss and material gain. The sample exposed to artificial saliva did not display significant changes in any parameter.

Influence of surface modification on droplet mobility during dropwise condensation

AbstractA two‐step surface fabrication technique is used to modify the wetting characteristics of copper sheets for heat transfer application. It consists of oxygen plasma treatment that results in the formation of surface nanostructures, and a post‐functionalization process using self‐assembled monolayers. The copper samples are characterized by contact angle measurements, scanning electron microscopy, and atomic force microscopy. Results show that surface roughness, described using hybrid and functional roughness parameters, varies with irradiation power. The plasma‐treated copper samples become superhydrophobic with water contact angles ranging from 150° to 160° after the post‐functionalization. Condensation experiments are conducted to explore the influence of surface wettability on condensate formation. Results show that droplets formed on the superhydrophobic copper sheets are smaller and more mobile with sweep events that are 9x more frequent compared to those on untreated copper sheets. Sweep events are shown to be influenced by surface porosity, which is defined using standard roughness parameters. It is demonstrated that higher surface porosity results to higher sweep interval.

Analysis of Circular Saw Tooth Marks Profile on Material Machined Surface After Filtering with Fast Fourier Transform (FFT)

The article presents theoretical analysis of machined surface roughness after sawing on circular saw and implementation of fast Fourier transform (FFT) as a possible simple filtering method for filtering out just the saw blade and saw tooth influence on the surface roughness. Surface roughness profile is represented as a signal that can be obtained as a sum of complex periodic signals that represent theoretical profile of tooth marks and lateral movement of tooth due to saw lateral movement and signals that represent structural roughness of wood combined with machining roughness, represented as a Gaussian noise. The application of FFT based filtering on such a signal can be effectively used to extract the main frequency components due to tool influence on total surface signal and the time domain of filtered signals display can then be obtained by use of the inverse Fourier transform. In order to test the theoretical assumptions, the machining tests in sawing of solid oak wood (Quercus robur L.) and medium density fiberboard (MDF) was conducted. Machined surface roughness was measured and analyzed in accordance with theoretical assumptions. It was concluded that a combination of discrete Fourier transform of surface roughness profile and standard roughness parameters can give a more complete representation of machined surface roughness after sawing with circular saws and that filtering of surface roughness profile signal with FFT filter can be used as a simple and effective method in quantifying tool influence on machined surface roughness after sawing on circular saw in varying machining conditions and on different workpiece material.

Fatigue behavior and modeling of additively manufactured IN718: The effect of surface treatments and surface measurement techniques

• Effect of five surface treatments on surface topography of LB-PBF IN718 was studied. • Surface measurements using optical microscopy and X-ray CT (XCT) were compared. • Surface profiles were constructed from XCT images by curving-fitting edge detection. • The effect of surface roughness was more significant in high cycle fatigue regime. • A modified fatigue notch factor model correlated surface parameters with fatigue life. In this study, the effect of various surface treatments, including sand-blasting, drag-finishing, turning, grinding, and grinding + drag-finishing, on surface roughness and fatigue properties of laser beam powder bed fused Inconel 718 was examined. The surface roughness values obtained from two surface measurement techniques, i.e., optical microscopy and X-ray computed tomography, were compared. Both surface measurement techniques consistently indicated that all surface treatments led to improvements in surface roughness, although optical microscopy was influenced by surface glares and overestimated the surface roughness values of drag-finished specimens. Accordingly, all surface treatments also led to improvement in fatigue resistance with sand-blasting and drag-finishing yielding the least while grinding + drag-finishing causing the most. Notably, only the cracks of grinding + drag-finished specimens initiated from crystallographic facets while those in other conditions were surface initiated. Furthermore, by treating the surface valleys as micro notches, an effective fatigue notch factor model using a hybrid surface roughness metric that incorporates several standard surface roughness parameters was shown to correlate the fatigue lives of 94 % of specimens with various surface conditions within a scatter band of three.

Surface roughness parameter and modeling for fatigue behavior of additive manufactured parts: A non-destructive data-driven approach

Metallic additive manufacturing produces undesired surface roughness due to the nature of the layer-by-layer fabrication process. As-built surface roughness can accelerate surface crack initiation and result in an early fatigue failure under cyclic loading. Therefore, the effect of surface roughness on the structural integrity of additive manufactured parts needs to be characterized before they can be used in fatigue-critical applications. In this study, the surface roughness of Ti-6Al-4V specimens fabricated by a laser beam powder bed fusion system is characterized, using a non-destructive data-driven approach, and correlated with their fatigue performance. Using a data-intensive surface topographical investigation, standard surface roughness parameters with statistical robustness are generated. The results confirm that conventional standard surface roughness parameters cannot appropriately represent the correlation between surface roughness and fatigue lives. Accordingly, a hybrid surface roughness parameter consisting of the maximum valley depth (Rv/Sv), the skewness (Rsk/Ssk), and the kurtosis (Rku/Sku) of the profiled lines/areas is suggested to explain the fatigue behavior. The proposed hybrid surface roughness parameter is validated by vertically fabricated flat specimens and diagonally built cylindrical dog-bone specimens to investigate the effect of design and build orientation. Moreover, a fatigue prediction model which considers the surface roughness as a micro-notch has been modified using the proposed hybrid surface roughness parameter and the part’s layer thickness and validated against experimental data.

Evaluating the Homogeneity of Surface Features Induced by Impact-Based Surface Treatments.

Impact surface treatments are well-known for their efficiency in enhancing the mechanical properties of metallic materials, especially under cyclic loadings. These processes, which encompass a wide range of surface treatments based on repetitive impacts of tools of various types, induce surface plastic deformation, compressive residual stresses, and grain refinement alter the surface roughness as a side effect. Thus, it is essential to have suitable indexes to quantify the surface features caused by the typically random nature of these treatments. Herein, we evaluated the rationality of using standard roughness parameters for describing the morphological characteristics of surfaces treated by shot peening as a representative and widely used treatment of the category. A detailed numerical model of the peening process was developed. The output data were elaborated to extract the surface roughness parameters following the standard procedures. The results revealed the validity of the surface roughness parameters to describe the topography of material treated with adequate surface coverage, also highlighting the necessity to use a set of parameters rather than the common practice of relying on single parameters. Not considering a comprehensive set of amplitude and spacing parameters can result in significant, inconsistent, and misleading results while comparing the performance of surfaces.

The influence of the pavement surface texture on the Pendulum Test Value

The article deals with the problem of finding a relation between surface texture and skid resistance represented by the Pendulum Test Value. For the texture measurements was used a new device that can capture surface irregularities up to the microtexture level. Besides Pendulum Test Values were also evaluated standard roughness parameters as well as the Mean Profile Depth widely used for pavement surface macrotexture evaluation. The texture parameters were evaluated for both macro- and micro-texture of all tested surfaces. Two groups of surfaces were measured. The first group, represented by reference surfaces with known parameters, was used for evaluation of the reliability of new device as well as for determining the relation between microtexture and pendulum test value. The second group was represented by asphalt mixture specimens designed to create various surfaces with different parameters of both macrotexture and microtexture. The obtained results show that there is no unambiguous direct relation between the size of irregularities and skid resistance. That means that high values of both macro and microtexture won’t have to necessarily mean a high level of friction. The proper size and proportion of both parts in their optimal combination are needed.

Surface finishing by laser re-melting applied to robotized laser metal deposition

Low surface quality of as-deposited laser metal deposition (LMD) parts is one of the main drawbacks of this additive manufacturing technology that prevents direct use without the implementation of costly and time consuming post-processes. An in-process surface finishing operation without the need of auxiliary equipment is highly appealing to overcome such issues. For this reason, laser re-melting performed with the same laser equipment used for the deposition process is a promising technology capable of redistributing the deposited material onto a smoother surface. Combined with a robotic manipulation system used for both the LMD and laser re-melting phases, complex geometries can potentially be produced in near net-shape conditions. An important issue concerning development of this process development regards the use of standardized roughness and waviness parameters, which can fail to address the texture specific to the LMD process. Indeed, the laser re-melting process can produce new texture formation under non-optimal conditions. Hence, an analysis of the surface topography in the frequency domain along with the standard surface roughness and waviness parameters would be more appropriate. In this work, laser re-melting is applied to AISI 316L thin walled structures right after the deposition process. An experimental campaign aimed at finding the process parameters and re-melting strategy capable of improving the surface quality was carried out. Areal surface profile measurements were used for characterizing the effect of the process parameters. The surface power spectrum on the S-F surface was calculated to point out the presence of periodical components in the surface structure and a transfer function calculation was performed to define the surface quality improvement in the frequency domain compared to the LMD as-deposited surface. The acquired surface areal data was assessed at two different spatial frequency regions corresponding to the S-L and L-F surfaces. The arithmetic average of the filtered surface areal data was used to calculate Sa, SF and Sa, LF analogously to the average roughness and waviness parameters of linear measurements respectively. Results showed, in the optimized conditions, a reduction of up to 79% in Sa, SF corresponding to the roughness related frequency range. On the other hand, the Sa, LF parameter corresponding to the waviness realted frequency range was reduced up to 58% due to the low effectiveness of laser re-melting in reducing the amplitude of the lowest frequency components. The overall improvement in terms of process capability was evaluated as mean ± 3 times the sample standard deviation values (µ±3σ). The average surface roughness Sa, SF could be reduced from 10.35±0.42 µm to 1.92±0.11 µm and average surface waviness Sa, LF from 9.57±0.48 µm to 4.04±0.20 µm.

Determination of an Objective Criterion for the Assessment of the Feasibility of an Instrumented Indentation Test on Rough Surfaces.

The influence of roughness on the results of indentation testing was investigated using a semianalytical model. This model used simulated surfaces that were described using three standard roughness parameters: the root-mean-square deviation Sq, the wavelength (or cut-off of Gaussian high-pass filter), and the fractal dimension. It was shown that Sq had the largest effect on the determination of the macrohardness, while the surface wavelength and fractal dimension had negligible effects at the scale of investigation. The error of determination of the macrohardness rose with the increase of the ratio Sq/hmax where hmax was the maximum indentation depth: Sq/hmax ratios lower than 0.02 were required to obtain a systematic error of the macrohardness lower than 5%, whatever the examined material mechanical properties (in elasticity and plasticity).

Development of virtual roughness comparators

The surface roughness is inspected visually or by the contact profiling method. In both cases, actual roughness comparators with the preset roughness parameters (Ra) are used. The reference surface is created by various technological impacts. Technological processes are influenced by random factors; therefore, the reference surface has the deviations of the Ra parameter from the declared value. We suggest to control the roughness based on its image. In this case, the data available is not enough to determine the standard roughness parameters. We introduce the rough surface parameter ζ, which uses the standard parameters Ra and Rz.We studied five images of roughness comparators made on glass using a New View 7300 white light interferometer. We determined the nominal value of the roughness parameter ζ for each roughness comparator and for each line of the rough surface images of 5 comparators. We considered the images of the reference surfaces as an indirect measurement of microrelief heights. We generated a reference rough surface based on the image of the actual surface of the roughness comparator. We used Spearman correlation coefficient to identify the most characteristic fragments of the reference rough surface. The virtual rough surface comparator created by us allows to increase the objectivity of visual control of rough surfaces and measure the similarity of the target and the reference rough surfaces.

Surface roughness of heat treated and untreated beech (Fagus sylvatica L.) wood after sanding

The effect of sanding, as the last operation before finishing, on the quality of heat treated wood surfaces has been insufficiently explored and explained. This paper compared the effects of sanding with three commonly used sanding grit sizes P60, P100, and P150 on the surface roughness values of beech (Fagus sylvatica L.) wood. The wood samples were treated by the ThermoWood process at 200 °C for 2.5 h. A large range of standard roughness parameters (Ra, Rq, Rv, Rt, RSm, Rsk, Rk, Rpk, and Rvk) and two waviness parameters (Wa, and Wt) were included in the analysis, as well as environmental scanning electron microscope (ESEM) images of the sanded surfaces. The results showed that the heat treatment slightly increased the surface roughness and decreased the wood surface waviness after sanding. All roughness and waviness parameters increased with increasing sanding mean grit diameters by following a strong linear correlation. The processing roughness was closely approximated by the parameter Rk. For both, treated and untreated beech, sanding had a tendency to obscure (in magnitude and number) wood anatomical details in the measured data. However, the influence of wood anatomy in the valleys domain increased as the grit size became finer.

Application of image edge detection methods for precise estimation of the standard surface roughness parameters: Polypropylene/ethylene-propylene-diene-monomer blend as a case study

Material surface roughness is an important property in different fields of science and its precise measurement is still a serious concern. Roughness measurement is commonly implemented using stylus profilometer. Although it suffers from some drawbacks such as low speed and destructive nature. Optical methods, such as machine vision coupled with image texture analysis have shown promising capability for noncontact/nondestructive roughness measurement. In the present study, a roughness evaluation method is proposed based on image edge detection algorithms. The method was applied to investigate the surface roughness of polypropylene/ethylene-propylene-diene-monomer (PP/EPDM) blend as an important engineering plastic. Different roughness patterns were created on PP/EPDM sheets employing hot press processing. Images of the roughened samples were captured with 10 different resolutions. In the proposed method, the performance of five different edge detectors including Roberts, Prewitt, Sobel, Laplacian of Gaussian (LoG), and Canny were examined. The results showed that LoG method in the images with 200 dpi resolution effectively evaluates PP/EPDM surface roughness. Linear correlation coefficients (R2) between LoG results and Stylus profilometry results was greater than 0.98. Moreover, some mathematical models were developed for evaluation of the roughness parameters based on LoG edge frequency. The models’ results showed 6.7% deviation from stylus profilometry results in the worst case. The proposed method can be used as a feasible solution for roughness evaluation of polymeric materials in online inspections.

Vision-based surface roughness evaluation system for end milling

ABSTRACTThis paper presents a vision-based surface roughness evaluation system for end-milled metals, addressing digital reconstruction and calibration of inspected surfaces, and quantitative and qualitative evaluation of surface texture. Specimens with different levels of surface roughness are machined, and a comparison between stylus-based and vision-based measurements is performed while using standard roughness parameters. The vison-based results vary among 9% and 11% compared to the stylus-based ones, which is a minor error to trade-off for faster measurements. Furthermore, surface texture evaluation is performed by detecting the generated cusp lines and tool marks on the machined surface. The tool marks’ distribution is analysed in order to determine whether the machining is performed under optimal cutting conditions. Results show that under optimal cutting conditions, the detected tool marks are normally distributed along the feed direction and the distance between two consecutive tool marks does not vary significantly. Based on the proposed methods software is implemented that enables the three-dimensional reconstruction, calibration and evaluation of the inspected surface.

Formation features and AFM studies of the silicon-chitosan-containing glycerohydrogel surface

Hybrid glycerohydrogels based on silicon tetraglycerolate and chitosan were produced by means of one-pot sol-gel synthesis. The influence of the component composition (the concentration of the template and precursor), the low-molecular-weight accelerator (NaCl), and the conditions of the process (pH, temperature) on the gelling duration was estimated. The glycerohydrogel surface microrelief was visualized by AFM in the semi-contact mode and the standard roughness parameters were calculated. The silicon-chitosan-containing glycerohydrogels were established to have a complex surface relief. Their solid sol-gel matrix is characterized by a uniform distribution of elements of the inorganic phase and a developed microporous structure with amorphous-crystalline ordering. The scale of the surface irregularities, as well as their structural and morphological features and the crystallinity degree of the solid sol-gel matrix, are determined by the template/precursor weight ratio and the molecular weight of the polymer.

Metrological Aspects of Surface Topographies Produced by Different Machining Operations Regarding Their Potential Functionality

AbstractThis paper presents a comprehensive methodology for measuring and characterizing the surface topographies on machined steel parts produced by precision machining operations. The performed case studies concern a wide spectrum of topographic features of surfaces with different geometrical structures but the same values of the arithmetic mean height Sa. The tested machining operations included hard turning operations performed with CBN tools, grinding operations with Al2O3ceramic and CBN wheels and superfinish using ceramic stones. As a result, several characteristic surface textures with the Sa roughness parameter value of about 0.2 μm were thoroughly characterized and compared regarding their potential functional capabilities. Apart from the standard 2D and 3D roughness parameters, the fractal, motif and frequency parameters were taken in the consideration.