Surface Topography Parameters Research Articles

Machine learning approach for the prediction of mixed lubrication parameters for different surface topographies of non-conformal rough contacts

PurposeThis study aims to use a machine learning (ML) model for the prediction of traction coefficient and asperity load ratio for different surface topographies of non-conformal rough contacts.Design/methodology/approachThe input data set for the ML model is generated using a mixed-lubrication model. Surface topography parameters (skewness, kurtosis and pattern ratio), rolling speed and hardness are used as input features in the multi-layer perceptron (MLP) model. The hyperparameter tuning and fivefold cross-validation are also performed to minimize the overfitting.FindingsFrom the results, it is shown that the MLP model shows excellent accuracy (R2 > 90%) on the test data set for making the prediction of mixed lubrication parameters. It is also observed that engineered rough surfaces with high negative skewness, low kurtosis and isotropic surface patterns exhibit a significant low traction coefficient. It is also concluded that the MLP model gives better accuracy in comparison to the random forest regression model based on the training and testing data sets.Originality/valueMixed lubrication parameters are predicted by developing a regression-based MLP model. The machine learning model is trained using several topography parameters, which are vital in the mixed-EHL regime because of the lack of regression-fit expressions in previous works. The accuracy of MLP with random forest models is also compared.

Comprehensive evaluation of surface parameter correlation in running-in wear process

The first wear process is running-in, which is a stage of each machine system must go through. The friction pair’s surface topography is an important feature of the running-in process. After running-in, the surface topography directly affects the performance in stable working state. The wear performance of the contact pair was focused on by mostly existing studies after a time; however, we should consider the correlation of the surface topography before and after running-in. In fact, exploration of this problem is significantly important to extend the service life of machine parts and improve the running performance. Based on the three-dimensional (3D) surface topography parameter evaluation method, in this study, experiments were designed to analyze the effect of the unworn surface topography on that after running-in, and investigated the correlation of 3D surface topography parameters. The results demonstrated that the topography characterization parameters, i.e., Sa, Sq, Sv, Sdc, Str, Sdq, and Sdr under different working conditions maintained a strong autocorrelation (the correlation coefficient of the same parameter). Moreover, the cross-correlation (the correlation coefficient between different parameters) among height parameters (Sq), hybrid parameters (Sdq, Sdr), and functional parameters (Sdc, Sk) was strong. The results of the surface roughness parameters found in this study can be used as input and output feature selection research based on working conditions and surface topography prediction after the modeling research of running-in surface topography.

Effects of flow velocity on biofilm composition and microbial molecular ecological network in reclaimed water distribution systems

The existence of biofilm on the reclaimed water pipeline seriously affects the safety of water distribution. And the flow regimes in the pipeline play a crucial role in the growth of biofilms. In this study, the biofilm composition, surface topography and bacterial community were detected under eight levels of flow velocity in the range of 0.10–1.40 m s−1. The results showed that the dry weight, the concentration of extracellular protein and extracellular polysaccharide in the biofilm reached a dynamic stable period after 640 h. The biofilm composition and surface topography of biofilm were significantly different under the different flow regimes (laminar flow belongs to [0.10, 0.19] m s−1, and turbulent flow belongs to [0.29, 1.40] m s−1). As the flow velocity range increases, the concentration of each component in the biofilm and the parameters of biofilm surface topography increased and then decreased. The flow velocity could be a strong environmental stimulus resulting in the succession of bacterial community in biofilm. As the flow velocity increased from 0.10 m s−1 to 1.40 m s−1, at the phylum level, the average relative abundance of Firmicutes mainly showed a trend of first increasing and then decreasing with the highest abundance value of 71.57% at 0.49 m s−1. The flow velocity increased from 0.10 m s−1 to 0.49 m s−1, a significant increase in microbial diversity could be detected. The increase in flow velocity promoted the proliferation of microorganisms, and the interaction between different microbial components was enhanced. At 0.49 m s−1, the function of the biofilm is complex, and the ability to resist environmental stress is the strongest. This study can effectively improve the cognition depth of biofilms under the influence of flow velocity in the reclaimed water distribution systems, and provide an important theoretical support for the safe distribution of reclaimed water.

A brief note on entire fracture surface topography parameters for 18Ni300 maraging steel produced by LB-PBF after LCF

The concept of entire fracture surface investigation is helpful in explaining fatigue phenomena. In this paper, this method has been applied for 18Ni300 maraging steel using a 3D measurement system. Before post-mortem analysis, the specimens produced by laser beam powder bed fusion (LB-PBF) were tested under low-cycle fatigue (LCF) for eight strain amplitudes in the interval 0.3% to 1.0%. The attention was placed on the relationship between the fatigue features, represented by the strain level and the fatigue life as well as the fracture surface topography evaluated in the form of areal, volume and fractal dimension parameters. It was found that fatigue life predictions calculated using the core material volume Vmc, obtained with the entire fracture surface method were within a scatter band with factors of ±1.5. The present results can be useful for the analysis of damaged structural elements exposed to LCF, especially for materials produced by additive manufacturing (AM). The outcomes of this brief note are important for the development of other fractographic methods and validation of fatigue life evaluation procedures.

Impact of light polarization on angle-resolved light scattering from gloss scale

The gloss scale is a set of coated paper samples with different surface roughness allowing for appearance variation from high gloss to mat. Nowadays, the gloss scale is widely used as a reference on visual appearance of glossy and mat surfaces. This work provides for angle resolved analysis of light scattering from gloss scales as well as the analysis of the surface topography parameters relevant for the analysis of light-scattering experiments: RMS-roughness σ, auto-correlation function and power spectrum density, correlation length ℓ c and surface slopes. The angle–resolved measurements of light scattered in reflection within the half–space are performed at 4 angles of incidence, while measurements within the incidence plane are made at 17 angles of incidence and under non–polarized, s–and p–polarized illumination. The polarization of incident light has a significant impact on both the specular and the diffused components of scattered light. Brewster scattering angle is especially well observed for black mat surfaces. Qualitative and quantitative analysis of measured scattered light is made with Rayleigh-Rice and Kirchhoff models applied to statistically representative analysis of surface topography.

An analysis of surface texture and wetting behavior for metal alloys produced by laser-powder bed fusion

The surface wetting behavior and its relationship with surface morphology of 3D-printed metal parts have attracted considerable attention, in large part due to the applicability of these components in fluid-related fields. In this study, the laser powder bed fusion (L-PBF) method was adopted to fabricate metal alloy parts with various materials, surface orientations, printing strategies and post-processing methods. The surface morphology and wettability of the fabricated parts were evaluated. By applying surface topography parameters, Sa, Spc and Sdr, the topographical distinctions between surfaces with various printing parameters were determined. Although both upskin and downskin surfaces are susceptible to spattered droplets and attachment of satellite particles, the results showed that more satellite particles were fused to the downskin surfaces due to greater reheating of underlying downskin surfaces, which resulted in the increased surface roughness of downskin surfaces. Post-processing methods including stress relief and EDM fluid had little effect on the surface topography, while the stress relief increased the surface hydrophobicity and EDM fluid increased the hydrophilicity. Moreover, the unusual surface superhydrophilicity was discovered on the downskin of 4340 and 316L parts. This work paves the way to systematically study the effect of materials, printing parameters, and post-processing methods on surface topography and wettability of the metal alloy made using L-PBF.

Elastic–plastic cylindrical rolling contact fatigue mechanism evolution and life prediction considering random surface topography

This paper proposes a semi-analytical fatigue life prediction method for the evolution of elastic–plastic cylindrical rolling contact fatigue mechanism under random surface topography, and reveals the evolution process of three contact fatigue mechanisms under high load conditions: micro-pitting, surface-originated pitting (SOP), and subsurface-originated spalling (SOS). Firstly, an elastic–plastic line contact model of random rough surface is proposed to analyze the contact condition between rolling elements considering random surface topography. Subsequently, a contact pressure spatial distribution model of rough surface is established, which can fully reflect the variation law of pressure distribution in the elastic–plastic stage. Finally, a semi-analytical life prediction (SALP) method is developed by combining the newly proposed analytical model with finite element method to illustrate the evolution process of the contact fatigue mechanism. The prediction accuracy of the SALP method is verified by comparing the results with those of the finite element method. Furthermore, the influence of random surface topography parameters (root mean square of roughness δ, correlation length λ) on contact fatigue life is further discussed, which helps to provide theoretical support for good surface process control for high-load rolling elements.

A numerical study on the impact of lubricant rheology and surface topography on heavily loaded non-conformal contacts

The increasing requirement of high-power density (power throughput/ weight) in modern day machines lead to thin film lubrication condition in various machine components (rolling element bearings, gears, cams, etc,) due to severe loading conditions. Surface roughness features and lubricant rheology plays a vital role in thin film lubrication, and significantly affects the lubrication performance and lifetime of machine components. The present work demonstrates surface topography and lubricant rheology effects on the traction coefficient for heavily loaded non-conformal contacts. The load-sharing concept considering elastic-plastic deformation of asperities, and Carreau shear-thinning rheological model is employed to describe the dry rough contacts and non-Newtonian behavior of lubricant. An influence of surface topography parameters such as roughness, skewness, kurtosis, and pattern ratio on the traction coefficient is discussed. From results, it is found that among different surface topographies, negatively skewed surfaces having isotropic surface pattern exhibit minimum traction coefficient. The load share function and the critical rolling speed are determined for various surface topographies which provides further insights into the surface topography effect on traction coefficient. The findings of present study are noteworthy as they provide a theoretical basis for an assessment of the lubrication performance of heavily loaded non-conformal contacts.

Fatigue life estimation of TMT reinforcing steel bar considering pitting corrosion and high temperature impacted surface topography

Surface topography of steel changes considerably when subjected to pitting corrosion and high temperature leading to a reduction in its fatigue life. Based on experiments, including microstructural studies and employing multiple linear regression methods, prediction models for surface topographic feature parameters such as arithmetic mean height, total height, ten-point height, profile mean spacing as a function of pitting severity, corrosion level severity, and temperature are developed. Using identical parameters, prediction models for surface topographic feature variable in stress concentration factor and defect size parameter are also developed. Further, a framework for estimating high-cycle fatigue life is proposed, incorporating the developed models. The proposed framework is validated by comparing the fatigue life estimated by incorporating the developed models with experimental data from the literature.

Experimental Investigation of Tribology-Related Topography Parameters of Hard-Turned and Ground 16MnCr5 Surfaces

Several surface topography parameters are available for the quantification of tribological properties of machined surfaces. Although these parameters and their influences are widely studied, there are contradictory findings due to the nature of the topography parameters, i.e., the behavior of different materials and cutting tool interactions lead to relatively varying numerical results. A comprehensive study of these interactions can contribute to more exact industrial machining applications. In this study, tribology-related 3D topography parameters of hard-machined (hard-turned and ground) surfaces were analyzed. The machining experiments were carried out based on a detailed design of the experiment; the analyzed material was case-hardened low-carbon content steel, which is widely used for automotive, industrial components such as bearings or gears. From the topography data, response function, correlation, and relative deviation analyses were carried out for the analyzed topography parameters, and tribology maps were created to support the selection of optimal cutting parameter values.

The Influence of Osteon Orientation on Surface Topography Parameters after Machining of Cortical Bone Tissue.

Mechanical processing of cortical bone tissue is one of the most common surgical procedures. A critical issue accompanying this processing is the condition of the surface layer, which can stimulate tissue growth and serve as a drug carrier. A comparison of the surface condition before and after orthogonal and abrasive processing was conducted to validate the influence of bone tissue's processing mechanism and orthotropic properties on the surface topography. A cutting tool with a defined geometry and a custom-made abrasive tool was used. The bone samples were cut in three directions, depending on the orientation of the osteons. The cutting forces, acoustic emission, and surface topography were measured. The level of isotropy and the topography of the grooves showed statistical differences relative to the anisotropy directions. After orthogonal processing, the surface topography parameter Ra was determined from 1.38 ± 0.17 μm to 2.82 ± 0.32. In the case of abrasive processing, no correlation was found between the orientation of osteons and topographical properties. The average groove density for abrasive machining was below 1004 ± 0.7, and for orthogonal, it was above 1156 ± 58. Due to the positive properties of the developed bone surface, it is advisable to cut in the transverse direction and parallel to the axis of the osteons.

The correlation of fractal dimension to fracture surface slope for fatigue crack initiation analysis under bending-torsion loading in high-strength steels

In this study, the fractal dimension of fatigue fracture surfaces is investigated in order to find an alternative failure loading indicator. Some of many metrological factors are generalized by reducing the fracture surface structure to one factor and develop an entire fracture surface procedure by analyzing the impact of surface slope and calculation resolution. Three notched geometries are studied under cyclic bending-torsion: 34CrNiMo6 high-strength steel bars with transverse blind holes; (ii) 34CrNiMo6 high-strength steel bars with lateral U-shaped notches; and (iii) 18Ni300 maraging steel hollow bars with transverse holes produced by selective laser melting. The surface topographies of fatigue fractures were measured with an optical profilometer. The bending-torsion ratio, maximum local von Mises equivalent stress and the number of cycles to crack initiation are examined using the fractal dimension. Moreover, a comparison was also made for conventional surface topography parameters such as root mean square height and void volume. A fatigue crack initiation model based on surface topography and loading conditions is proposed. The model relies on the product of the maximum local von Mises equivalent stress and the fractal dimension divided by the root mean square height to void volume ratio. The results show that the fracture plane geometry, expressed by the fractal dimension Df, can facilitate the estimation of post-failure loading history. In particular, the analysis based on the enclosing boxes method (EBM) is more accurate when it is used as an extra-fine resolution without any plane leveling.

Influence of the Size of Measurement Area Determined by Smooth-Rough Crossover Scale and Mean Profile Element Spacing on Topography Parameters of Samples Produced with Additive Methods

Surface topography measurements are becoming more and more popular and complement the 2D analysis of surface texture. The selection of the measurement area is not yet included in the standards, and the size of this area affects the values of the determined parameters. The article presents the results of research on determining the measurement area based on the smooth-rough crossover scale (SCR) and mean profile element spacing (Rsm) parameters. The tests focused on measuring the surface topography of random and directional types of polymer parts produced by various additive manufacturing techniques. The measurements were conducted using the focus variation method. Surface topography parameters were determined for large evaluation areas determined based on the cut-off filter length Lc and for small areas defined based on the SCR and Rsm parameters. The values of parameters determined from large areas constituted the reference values to which the values determined from small areas were compared. In the case of random-type samples, it was shown that the values of the parameters calculated from smaller areas determined based on the SCR significantly differed from the reference values. For both types of samples, determination of the evaluation area based on the Rsm yielded good results. In most cases, the greatest differences between the values of parameters calculated for small and large areas were noted for the Ssk and Smr1 parameters. Based on the test results, it could be advantageous to replace the measurement of a larger area with the measurement of several smaller areas located at different places on the sample.

ANALYSIS OF SELECTED FUNCTION-DEFINING 2D SURFACE ROUGHNESS PARAMETERS IN TANGENTIAL TURNING

Among other, more frequently analysed surface topography parameters, the function-defining parameters must be analysed in different machining procedures to outline their application possibilities. These values are the core roughness, the reduced peak height, the reduced valley depth, the skewness, and the kurtosis of the roughness profiles. Tangential turning is a promising machining procedure, which can produce ground-like surfaces with twist-free properties by defined cutting edged tools. The achievable productivity is also very high. Therefore, in this paper, these roughness parameters were analysed from 2D roughness profiles measured on surfaces machined by tangential turning.

Fractographic-fractal dimension correlation with crack initiation and fatigue life for notched aluminium alloys under bending load

In this study, fatigue fracture surfaces of aluminium alloy 2017-T4 notched specimens were investigated under cyclic bending to find an alternative failure loading index.. The surface topographies were measured on the entire fracture area with an optical profilometer for different loading conditions. Fatigue crack initiation life Ni and total fatigue life Nf were examined using standard surface topography parameters (such as, root mean square height Sq, arithmetical mean height Sa, maximum height Sz) and non-standard surface topography parameters (such as, fractal dimension Df). Fatigue life assessment was successfully performed by combining both fracture surface topography and stress state features. The results show that the fracture plane geometry, expressed by the fractographic-fractal dimension, can facilitate the estimation of post-failure loading history.

Investigation of Selected Surface Topography Parameters and Deformation during Milling of Vertical Thin-Walled Structures from Titanium Alloy Ti6Al4V.

Thin-walled elements are widely used in the aerospace industry, where the aim is to reduce the process time and the weight of the structure while ensuring the sufficient quality of the finished product. Quality is determined by geometric structure parameters and dimensional and shape accuracy. The main problem encountered during the milling of thin-walled elements is the deformation of the product. Despite the various methods available for measuring deformation, more are still being developed. This paper presents selected surface topography parameters and deformation of vertical thin-walled elements during an experiment under controlled cutting conditions for samples from titanium alloy Ti6Al4V. Constant parameters of feed (f), cutting speed (Vc,) and tool diameter (D) were used. Samples were milled using a tool for general-purpose and a tool for high-performance machining, as well as two different machining approaches: with greater involvement of face milling, and cylindrical milling with a constant material removal rate (MRR). For samples with vertical thin walls, the parameters of waviness (Wa, Wz,) and roughness (Ra, Rz) were measured using a contact profilometer in the selected areas on both processed sides. Deformations were determined in selected cross-sections perpendicular and parallel to the bottom of the sample using GOM measurement (GOM-Global Optical Measurement). The experiment showed the possibility of measuring deformations and deflection arrows of thin-walled elements proceeded from titanium alloy using GOM measurement. Differences in selected surface topography parameters and deformations were observed for the machining methods used with an increased cross-section of the cut layer. A sample with a deviation of 0.08 mm from the assumed shape was obtained.

Study of surface topography parameters during shot peening process and their influence on the paint coating of adhesion

Study of surface topography parameters during shot peening process and their influence on the paint coating of adhesion

Performance of Surface Topography Systems in Scoliosis Management: A Narrative Review

ABSTRACT Introduction The aesthetic appearance of the torso is the foremost concern of scoliotic patients, which, if not addressed, could adversely affect their life quality. The Cobb angle limitation in describing three-dimensional (3D) deformities of the spine and its associated ionizing radiation motivated clinicians to implement noninvasive surface topography (ST) methods for monitoring scoliosis. This study aimed to review the accuracy of the most commonly used ST systems and their ST parameters in predicting and monitoring scoliosis. Materials and Methods The scientific databases were used to search for the studies considering the validity and reliability of different ST methods published in English from 1970 to July 2020. Results Of 221 found publications, 41 journal publications were evaluated for this review. The accuracy of ST methods was affected by light source quality, acquisition time, and postural sway. Some ST parameters resulted in a high correlation with radiographic measurements and classified scoliosis deformities into mild, moderate, and severe. Some ST parameters may not effectively predict the Cobb angle but could monitor curve progression accurately. Representing spine deformities in the lumbar section and subjects with higher body mass index was associated with more significant errors due to thicker soft tissues around the spine. Conclusions According to the present review, ST systems could complement radiography measurements and provide valuable insights into different aspects of internal and external deformity; however, they have not reached a state that can replace radiography in the management of scoliosis. Clinical Relevance The present study helps clinicians choose the most appropriate ST methods for predicting and monitoring scoliotic curves and torso asymmetry evaluations.

Influence of Antibacterial Coating and Mechanical and Chemical Treatment on the Surface Properties of PA12 Parts Manufactured with SLS and MJF Techniques in the Context of Medical Applications

Additive manufacturing (AM) is a rapidly growing branch of manufacturing techniques used, among others, in the medical industry. New machines and materials and additional processing methods are improved or developed. Due to the dynamic development of post-processing and its relative novelty, it has not yet been widely described in the literature. This study focuses on the surface topography (parameters Sa, Sz, Sdq, Sds, Str, Sdr) of biocompatible polyamide 12 (PA12) samples made by selective laser sintering (SLS) and multi jet fusion (MJF). The surfaces of the samples were modified by commercial methods: four types of smoothing treatments (two mechanical and two chemical), and two antibacterial coatings. The smoothing treatment decreased the values of all analyzed topography parameters. On average, the Sa of the SLS samples was 33% higher than that of the MJF samples. After mechanical treatment, Sa decreased by 42% and after chemical treatment by 80%. The reduction in Sdq and Sdr is reflected in a higher surface gloss. One antibacterial coating did not significantly modify the surface topography. The other coating had a smoothing effect on the surface. The results of the study can help in the development of manufacturing methodologies for parts made of PA12, e.g., in the medical industry.

Experimental study on the cytocompatibility of milling surface of poly-ether-ether-ketone (PEEK)

Poly-ether-ether-ketone (PEEK) is widely used in biomedical science because of its biocompatibility. However, the material is biologically inert. Many works have showed the potentiality of surface modification technique to enhance its biological performance, such as surface coating and impregnating bioactive materials into its substrate. Even so, these techniques are low efficiency or inapplicable in processing parts with complex structure. This thesis presents an experimental work of milling for the surface modification of PEEK, and its impact on the biological response is addressed. First, the influence of milling parameters on machined surface topography features is discussed based on the Taguchi method and end milling experiments. And then, the effect of the machined surface topography on the viability of fibroblasts is investigated by using cells from a mouse fibroblast L929 and the agar overlay test, MTT test. The experimental result indicated that there is a certain surface topography (characterized by Ssk = 0.011), which ensures the highest possible cells viability, but a significant decrease of L929 viability started with the surface roughness of Sa = 1.18 μm. The axial and radial depths of cut are the two most critical factors to affect surface topography parameters. It is concluded that the milling process significantly affects surface topography of PEEK, which in turn influences the L929 viability.