Surface Microgeometry Research Articles

ШЕРОХОВАТОСТЬ ПОВЕРХНОСТИ ПРИ ОБРАБОТКЕ ПОЛИМЕРНО-АБРАЗИВНЫМИ КРУГАМИ

The PURPOSE of the paper is to determine the influence patterns of the parameters of surface machining (cutting speed, tool feed and deformation) by polymer abrasive wheels on the roughness of the machined surface and develop a mathematical model of microrelief formation of this surface. METHODS. The study involves analytical and experimental methods using the wheels of the company 3M (Minnesota Mining and Manufacturing Company) of the brands Scotch-Brite™ FS-WL, DB-WL, CF-FB of different coarseness. RESULTS AND THEIR DISCUSSION. We have developed a mathematical model of roughness formation based on the interaction of an elastic abrasive wheel cutting microrelief and a machined surface. Abrasive grains are introduced into the machined material under cutting microrelief interaction with the processed surface. The average depth of grain introduction has been determined by the set mechanical properties of the machined material and the vertical component of the cutting force taking into account lapping and elastic recovery of scratches. This depth is represented by the height of the machined surface roughness. Experimental check of the cutting speed and feed on the samples made of V95pchT2 alloy at various deformations of a wheel has shown close agreement of experimental and theoretical results. CONCLUSION. The developed theory of part surface microgeometry formation allows analytical determination of roughness by the known parameters of the tool depending on the processing modes. Having optimized the technological process, this mathematical model can be used as a restricting function for the achievement of the set optimization criterion, for example, the criterion of target economic function.

Appearance Modeling via Proxy-to-Image Alignment

Endowing 3D objects with realistic surface appearance is a challenging and time-demanding task, as real-world surfaces typically exhibit a plethora of spatially variant geometric and photometric detail. Not surprisingly, computer artists commonly use images of real-world objects as an inspiration and a reference for their digital creations. However, despite two decades of research on image-based modeling, there are still no tools available for automatically extracting the detailed appearance (microgeometry and texture) of a 3D surface from a single image. In this article, we present a novel user-assisted approach for quickly and easily extracting a nonparametric appearance model from a single photograph of a reference object. The extraction process requires a user-provided proxy, whose geometry roughly approximates that of the object in the image. Since the proxy is just a rough approximation, it is necessary to align and deform it so as to match the reference object. The main contribution of this work is a novel technique to perform such an alignment, which enables accurate joint recovery of geometric detail and reflectance. The correlations between the recovered geometry at various scales and the spatially varying reflectance constitute a nonparametric appearance model. Once extracted, the appearance model may then be applied to various 3D shapes, whose large-scale geometry may differ considerably from that of the original reference object. Thus, our approach makes it possible to construct an appearance library, allowing users to easily enrich detail-less 3D shapes with realistic geometric detail and surface texture.

Formation of the surface roughness during grinding with flap wheels after shot peening

Shot peening is widely used in forming long panels and sheaths. Due to impact by shot on the processed surface, a specific microgeometry is formed, the characteristic feature of this microgeometry are the numerous dimples as the traces of shot impact with different diameters and depths. A presence of these dimples causes deterioration of the surface roughness parameters. Therefore, after shot peening the mandatory requirement is the implementation of surface grinding with flap wheels for partial removal of the dimples. The size of the assigned allowance for grinding depends on the quality requirements of the part surface. At the same time, the depths of the remaining dimples are determined by the part surface roughness requirements. After grinding, the new surface microgeometry is formed, as a combination of micro-roughness from previous types of processing and the remained dimples in result of shot peening. In this work the microgeometry formation of surface layer of the samples after shot peen forming and subsequent grinding with flap wheels was analysed. The parameters of surface roughness were measured by the method of three-dimensional optical scanning. In the measurement result, the mathematical model of the surface micro-profile formation was formulated, the analytical dependences of the position of the center plane and the arithmetic mean deviation of profile were obtained.

Contact Stiffness of Machine Components and the Influence of the Microgeometry of the Contact Surfaces on It

The use of characteristics of the contact stiffness in the scientific literature to describe a discrete contact between machine components under normal and tangential loading has been analyzed. The application of a model of the discrete contact of rough surfaces, as well as the influence of the parameters of the contact surface microgeometry on the contact stiffness under normal and tangential loadings and shear has been studied.

Effect of Adherend Surface Microgeometry on Adhesively Bonded Joint Strength

Effect of Adherend Surface Microgeometry on Adhesively Bonded Joint Strength

Inverse wear contact problem of the friction unit

In this study, theoretical analysis for defining the function of displacements of a hub’s external contour points and microgeometry of the friction unit providing the absence of initial wear that holds to the end of running-in period, was carried out based on a rough friction surface model. A closed system of algebraic equations admitting to obtain the solution of the problem of optimal design of a friction unit depending on the geometrical and mechanical characteristics of a hub and plunger was constructed. The found function of displacements of the hub’s external contour points and microgeometry of friction surface provide wear resistance increase of friction pair. Calculations for friction units applied to the borehole sucker–rod oil pumps were considered as an example.

Corrosion of Nickel-Titanium Orthodontic Archwires in Saliva and Oral Probiotic Supplements.

ObjectivesThe aim of the study was to examine how probiotic supplements affect the corrosion stability of orthodontic archwires made of nickel-titanium alloy (NiTi).Materials and MethodsNiTi archwires (0.508x0.508 and having the length of 2.5 cm) were tested. The archwires (composition Ni=50.4%, Ti=49.6%) were uncoated, nitrified and rhodium coated. Surface microgeometry was observed by using scanning electron microscope and surface roughness was measured by profilometer through these variables: roughness average, maximum height and maximum roughness depth. Corrosion was examined by electrochemical method of cyclic polarisation.ResultsRhodium coated alloy in saliva has significantly higher general corrosion in saliva than nitrified alloy and uncoated alloy, with large effect size (p=0.027; η2=0.700). In the presence of probiotics, the result was even more pronounced (p<0.001; η2=0.936). Probiotic supplement increases general and localised corrosion of rhodium coated archwire and slightly decreases general corrosion and increases localised corrosion in uncoated archwire, while in the case of nitrified archwire the probability of corrosion is very low. The differences in surface roughness between NiTi wires before corrosion are not significant. Exposure to saliva decreases roughness average in rhodium coated wire (p=0.015; η2=0.501). Media do not significantly influence surface microgeometry in nitrified and uncoated wires.ConclusionProbiotic supplement affects corrosion depending on the type of coating of the NiTi archwire. It increases general corrosion of rhodium coated wire and causes localised corrosion of uncoated and rhodium coated archwire. Probiotic supplement does not have greater influence on surface roughness compared to that of saliva.

Parameters Selection for Electropolishing Process of Products Made of Copper and Its Alloys

AbstractElectropolishing is electrochemical method used in metal working that has a vital role in production of medical apparatus, in food or electric industry. The purpose of this paper is to determine optimal current parameters and time required for conducting electropolishing process from the perspective of changes of surface microgeometry. Furthermore, effect of different types of mechanical working used before electropolishing on final surface state was evaluated by observation in changes of topography. Research was conducted on electrolytic copper and brass. Analysis of surface geometry and its parameters (Ra, Sa) was used as criterion describing efficiency of chemical electropolishing. Results of the experiment allow for current parameter optimization of electrochemical polishing process for selected non-ferrous alloys with preliminary mechanical preparation of the surface.

Combined effect of surface microgeometry and adhesion in normal and sliding contacts of elastic bodies

In this study, models are proposed to analyze the combined effect of surface microgeometry and adhesion on the load–distance dependence and energy dissipation in an approach–separation cycle, as well as on the formation and rupture of adhesive bridges during friction. The models are based on the Maugis–Dugdale approximation in normal and frictional (sliding and rolling) contacts of elastic bodies with regular surface relief. For the normal adhesive contact of surfaces with regular relief, an analytical solution, which takes into account the mutual effect of asperities, is presented. The contribution of adhesive hysteresis into the sliding and rolling friction forces is calculated for various values of nominal pressure, parameters of microgeometry, and adhesion.

An Analytical Model of Mechanistic Wear of Polymers

This paper proposes a wear model for polymers based on so-called mechanistic processes comprising both low cycle fatigue and abrasive wear mechanisms, which are prominent in polymer–metal sliding interfaces. Repeated elastic contact causes localized fatigue, whereas abrasive part is an anticipatory outcome of plastic contacts by hard metal asperities on to soft polymer surface. Further, presuming adhesive interactions in elastic–plastic contacts, asperity contact theories with necessary modifications were analyzed to assess load and separation for their subsequent use in elementary wear correlations. Both Gaussian and Weibull distributions of asperity heights were considered to include statistics of surface microgeometry. Finally, volumetric wear was written in terms of roughness parameters, material properties, and sliding distance. Validation was conducted extensively, and reliability of the formulation was achieved to a large extent. Experimental part of this work included several pin-on-disk tests using polyether ether ketone (PEEK) pins and 316L stainless steel disks. Disks with different roughness characteristics generated by polishing, turning, and milling were tested. Experimental results agreed well with predictions for the polished surface and with some deviations for other two surfaces. Further, fatigue to abrasive wear ratio was identified as an analytical tool to predict prevailing wear mechanism for polymer-metal tribo-systems. After examining the considered cases, it was both interesting and physically intuitive to observe a complete changeover in wear mechanisms following simply an alteration of roughness characteristics.

Assessment of gas turbine engine airfoil surface microstructure

We propose a new approach to the assessment of surface roughness of gas turbine engine airfoil after polishing. The micro-geometry of the blade surfaces was investigated with the use of an electrooptical system on the basis of computing the average amplitude of the variable component of the autocorrelation function obtained as a result of computer processing of the surface video images. The use of the electrooptical method of assessing the surface micro-geometry of compressor blades and turbine blades makes it possible to construct the fields of surface roughness and stress concentration factor, as well as to analyze the technology of finishing treatment in more depth.

Surface microgeometry of structural-steel samples after diamond burnishing

The influence of diamond burnishing on the surface microgeometry of 30ХГСН2А-ВД structural alloy steel is considered. Empirical formulas are presented for the surface roughness as a function of the burnishing parameters.

Minimization of the thermal state of the hub of a friction pair

ABSTRACTTheoretical analysis for defining the function of displacements of a hub’s external contour points and the microgeometry of the friction surface, ensuring minimization of the thermal state of the hub of a friction pair, is performed based on the model of rough friction surfaces and minimax criterion. A closed system of algebraic equations is constructed, allowing the solution to the problem of the optimal design of the friction pair to be obtained, depending on geometric and thermophysical characteristics of the hub and plunger. The resulting functions of displacements of the hub’s external contour points and microgeometry of the friction surface ensure the increased serviceability of the friction pair.

Automated control of component surface microgeometry using graphic images of the profiles

Automated control of component surface microgeometry using graphic images of the profiles

Effect of the Method for Treatment of the Functional Surface of a Piezoelectric Vibration Sensor on its Sensitivity

The investigation has been performed for the possibilities to improve the operating characteristics of aviation vibration sensors without increasing the cost price of their manufacture due to optimization of the microgeometry of functional surfaces. The goal of investigation is to develop a set of procedures for modernisation of the process of manufacture of parts for the vibration sensor providing the optimum microgeometry of their functional surfaces. The investigation has been carried out with the use of computer simulation method and experimentally. The microgeometry of functional surfaces has been described by means of graphical criteria. The Taguchi method has been used for planning full-scale experiments on machining of functional surfaces. The computer model of the vibration sensor design has been developed allowing to evaluate the effect of deviation of the relative position of functional surfaces of the sensor on its functional characteristics, the experimental and design data have been compared. As a result of investigation, the relationship between process factors and sensitivity of the vibration sensor has been identified and described, the optimum process parameters of treatment at manufacturing the functional surface, which provide its best sensitivity, have been determined.

Fractal microgeometry of original and hydgrogen-charged graphene multilayer films surface: research by the low-temperature sorption of nitrogen method

Changes in the surface microgeometry of multilayer graphene films, as a result of hydrogen adsorption (1% mass.), have been examined by the method of low-temperature fractal sorption of nitrogen. It is established that hydrogen atmosphere treatment leads to the significant development of graphene surface and lowers the first layer heat adsorption from 289 down to 260J/kg. There have been found out as well the overall mesopores concentration growth and pore size distribution function broadening. At that, the surface fractal dimension value has grown from 2,52 up to 2,67, which is to give us an evidence of the surface chaotization as a result of hydrogen withdrawal into the atmosphere and the graphene surface erosion.

A comparative study of methods for treating the end effects in surface finish measurement

Surfaces in engineering can be considered as a weighted overlapping of various sinusoidal components which can be separated by their wavelength. The study of the influence of surface micro-geometry on the functional behavior of the pieces requires the separation of these components. This separation is carried out by applying filtering techniques to the digitized values representing the considered profile or surface. Most widespread filtering techniques, such as the Gaussian filtering, are based on a convolution between the points of the surface with a weighting function. While convolution is being performed, those points near to the ends of the sample length have not enough information to rightly perform the convolution and the phenomenon known as end effect appears consequently. The present work makes a comparative analysis between different criteria proposed by the ISO standards to reduce the impact caused by the appearance of the end effects.

The impact of microgeometry pistons with a stepped bearing surface for the friction loss of the internal combustion engine

This paper present the results of experimental piston friction losses on stepped bearing surface microgeometry obtained on the test rig. This test rig is equipped with special temperature control system, which provides better stability to temperature than in standard systems. The results of station tests was discussed. Tests was analyzed depending the moment caused by the friction on the oil temperature in the oil sump. Specified conclusions allow to assess the impact of the stepped profile of the pistons bearing surface microgeometry for different values of engine speed and the oil temperature at the friction losses in the main kinematic engine node which is piston-cylinder.

Surface microgeometry after selective laser sintering of metal powder

A multifactorial model is proposed for the surface microgeometry after selective laser sintering of metal powder. The dependence of the microgeometry on the following dominant factors is established: the laser power, the speed of the laser beam, and the scanning increment.

Functional surface microgeometry providing the desired performance of an aircraft vibration sensor

Functional surface microgeometry providing the desired performance of an aircraft vibration sensor