Surface Microgeometry Research Articles

Experimental investigation and numerical analysis of material removal efficiency using abrasive microaggregates in grinding processes of Ti6Al4V

Reducing plastic interactions between abrasive grains and the material being processed improves grinding efficiency and lowers energy consumption. Widening the cutting zone with abrasive grains enhances chip formation and reduces lateral material displacement. This can be achieved by using abrasive microaggregates.The paper presents an experimental analysis of grinding with modified wheels containing abrasive microaggregates. It examines how these microaggregates impact the grinding wheel's surface microgeometry and material removal efficiency. The study measured changes in the number, surface area, volume, and spacing of active contact areas on the grinding wheel active surface. A comparative analysis using the Shos indicator showed that abrasive microaggregates promote the formation of active areas with wide cutting edges perpendicular to the cutting direction.Finite element method simulations confirmed that abrasive microaggregates enhance material removal by widening the micro-cutting zone and increasing lateral resistance, which reduces the formation of flashes along the cutting path. The study also assessed how these surface features impact the roughness of the ground surface. A comparative analysis of roughness parameters showed a statistically significant reduction in surface, volume, hybrid, and functional parameters when using grinding wheels with abrasive microaggregates. This analysis was conducted using bootstrap statistical hypothesis tests.

Features of Increasing the Wear Resistance of 90CrSi Tool Steel Surface under Various Electrophysical Parameters of Plasma Electrolytic Treatment

The paper investigates the feasibility of plasma electrolytic treatment (PET) of 90CrSi tool steel to enhance hardness and wear resistance. The influence of electrophysical parameters of PET (polarity of the active electrode, chemical-thermal treatment, and polishing modes) on the composition, structure, morphology, and tribological properties of the surface was studied. Tribological tests were carried out under dry friction conditions according to the shaft-bushing scheme with fixation of the friction coefficient and temperature in the friction contact zone, measurements of surface microgeometry parameters, morphological analysis of friction tracks, and weight wear. The formation of a surface hardened to 1110–1120 HV due to the formation of quenched martensite is shown. Features of nitrogen diffusion during anodic PET and cathodic PET were revealed, and diffusion coefficients were calculated. The wear resistance of the surface of 90CrSi steel increased by 5–9 times after anodic PET followed by polishing, by 16 times after cathodic PET, and up to 32 times after subsequent polishing. It is shown that in all cases, the violation of frictional bonds occurs through the plastic displacement of the material, and the wear mechanism is fatigue wear during dry friction and plastic contact.

A mechano-regulation model to design and optimize the surface microgeometry of titanium textured devices for biomedical applications

In a technological context where, thanks to the additive manufacturing techniques, even sophisticated geometries as well as surfaces with specific micrometric features can be realized, we propose a mechano-regulation algorithm to determine the optimal microgeometric parameters of the surface of textured titanium devices for biomedical applications. A poroelastic finite element model was developed including a portion of bone, a portion of a textured titanium device and a layer of granulation tissue separating the bone from the device and occupying the space between them. The algorithm, implemented in the Matlab environment, determines the optimal values of the root mean square and the correlation length that the device surface must possess to maximize bone formation in the gap between the bone and the device. For low levels of compression load acting on the bone, the algorithm predicts low values of root mean square and high values of correlation length. Conversely, high levels of load require high values of root mean square and low values of correlation length. The optimal microgeometrical parameters were determined for various thickness values of the granulation tissue layer. Interestingly, the predictions of the proposed computational model are consistent with the experimental results reported in the literature. The proposed algorithm shows promise as a valuable tool for addressing the demands of precision medicine. In this approach, the device or prosthesis is no longer designed solely based on statistical averages but is tailored to each patient's unique anthropometric characteristics, as well as considerations related to their metabolism, sex, age, and more.

Comparison of Friction Properties of GI Steel Plates with Various Surface Treatments

This article presents the improved properties of GI (hot-dip galvanized) steel plates in combination with a special permanent surface treatment. The substrate used was hot-dip galvanized deep-drawn steel sheets of grade DX56D + Z. Subsequently, various surface treatments were applied to their surface. The coefficient of friction of the metal sheets without surface treatment, with a temporary surface treatment called passivation, and a thin organic coating (TOC) based on hydroxyl resins dissolved in water, Ti and Cr3+ were determined by a cup test. The surface quality and corrosion resistance of all tested samples were also determined by exposing them for up to 288 h in an atmosphere of neutral salt spray. The surface microgeometry parameters Ra, RPc and Rz(I), which have a significant influence on the pressing process itself, were also determined. The TOC deposited on the Zn substrate was the only one to exhibit excellent lubrication and anticorrosion properties, resulting in the lowest surface microgeometry values owing to the uniform and continuous layer of the thin organic coating compared to the GI substrate and passivation surface treatment, respectively.

FEATURES OF THE FORMATION OF THE NANOSTRUCTURAL STATE OF THE SURFACE LAYER OF STEEL PARTS DURING PROCESSING AND OPERATION

Considered patterns of formation of the nanostructural state of the surface layer of machine parts during friction under conditions of complex dynamic loading. The results of the complex assessment of the state of the surface layer of samples after friction continuous indentation and scanning methods indenter, an analysis of changes in the work function of the electron from the surface of the samples. Shown that during the friction of steel surfaces, an increase in transverse slippage contributes to the formation of a more uniform surface layer. This decreases its strength, wear resistance, and a more uniform surface microgeometry. This is accompanied by a decrease in the magnitude and spread of the electron work function over the surface. The relationship between the nanostructural state of a polished surface and roughness and reflectivity is presented.

A Study of 2D Roughness Periodical Profiles on a Flat Surface Generated by Milling with a Ball Nose End Mill.

This paper presents a study of 2D roughness profiles on a flat surface generated on a steel workpiece by ball nose end milling with linear equidistant tool paths (pick-intervals). The exploration of the milled surface with a surface roughness tester (on the pick and feed directions) produces 2D roughness profiles that usually have periodic evolutions. These evolutions can be considered as time-dependent signals, which can be described as a sum of sinusoidal components (the wavelength of each component is considered as a period). In order to obtain a good approximate description of these sinusoidal components, two suitable signal processing techniques are used in this work: the first technique provides a direct mathematical (analytical) description and is based on computer-aided curve (signal) fitting (more accurate); the second technique (synthetic, less accurate, providing an indirect and incomplete description) is based on the spectrum generated by fast Fourier transform. This study can be seen as a way to better understand the interaction between the tool and the workpiece or to achieve a mathematical characterisation of the machined surface microgeometry in terms of roughness (e.g., its description as a collection of closely spaced 2D roughness profiles) and to characterise the workpiece material in terms of machinability by cutting.

Comparative structural analysis of samples of transpedicular screws from titanium alloys

The article presents studies of transpedicular screws made of titanium alloy BT6. A metallographic and microstructural analysis of screw blanks, prototypes of transpedicular screws made of BT6 alloy and commercially produced screws made of Ti-6Al-4V was performed. Specimens of transpedicular screws were manufactured using the vortex thread cutting method on a CITIZEN Cincom K16E-VII automatic lathe. The microgeometry of the screw surface was created by sandblasting using quartz sand as an abrasive material. Studies have shown that experimental and foreign samples of transpedicular screws have a similar microstructure, consisting of globular crystals of the β-phase located in a light matrix of the α-phase. The microhardness of the rod part of the screw made of Ti-6Al-4V alloy was 312...338 HV, the microhardness of the material of the prototypes was from 264 to 394 HV. Conclusions have been drawn that determine the feasibility of choosing rods made of titanium alloy BT6 as a blank for the manufacture of transpedicular screws.

Hodnotenie zmeny mikrogeometrie kovového povrchu vzhľadom na aplikačnú dobu fosfátovania

The contribution is focused on the analysis of the microgeometry of metal surfaces after applying a conversion layer using phosphating. The types of basic materials used in the experiment are uncoated deep drawn steel DC04 and hot-dip galvanized microalloy steel HX340LAD+Z. During the application of the conversion layer, the changes of the microgeometry parameters of the surfaces were studied with respect to the phosphating time, which was 3, 5 and 10 minutes. The paper also deals with the statistical evaluation of roughness parameters of pre-treated surfaces. The achieved results provide information for other technological operations such as the creation of adhesive joints, where the correct anchoring of the adhesive is important for the load-bearing capacity of the joints.

Применение ультразвука в процессе аддитивного производства пластиковых деталей

Despite huge prospects for the layer-by-layer synthesis of products, which makes it possible to produce parts of a unique shape, the widespread use of the method face the problems of making a proper microgeometry of the product surface, which due to the peculiarities of layer-by-layer production is rather rough, and mechanical methods of machine working often do not admit the possibility of figure-shaped parts post processing. The article studies the problem of ensuring the quality of the plastic parts surface layer obtained by additive technologies. For this purpose, it is proposed to use ultrasonic processing technologies. The existing methods of using ultrasonic vibrations in the production of plastic parts are analyzed: the manufacture of wire for 3D printing with additives, which results in an increase in the mechanical properties of the product. Besides, liquid treatment of a solvent-loaded product in order to remove supporting elements. Studies have been carried out on the finishing of parts in a solvent aerosol obtained by ultrasonic spraying. This method has a number of advantages in comparison with the treatment in solvent vapors obtained during its heating, which include the possibility of regulating the size of droplets, their moving speed, aerosol concentration, caused by changing the modes of ultrasonic treatment. As a result of experimental studies, it is found that the use of this treatment method eventuates an increase in the quality of the sample surfaces to be worked, and besides, it reduces the height parameters of roughness in the direction perpendicular to the layered growth of the product by more than a factor of ten. The mechanism of changing the microgeometry of the surface is as follows: when aerosol droplets contact the surface, part of the material forming the protrusions dissolves and fills valleys, while in the liquid state; after finishing the work, the material polymerizes, generating a surface with improved features.

Revisiting Maxwell-Smoluchowski theory: Low surface roughness in straight channels

The Maxwell-Smoluchowski (MS) theory of gas diffusion is revisited here in the context of gas transport in straight channels in the Knudsen regime of large mean free path. This classical theory is based on a phenomenological model of gas-surface interaction that posits that a fraction ϑ of molecular collisions with the channel surface consists of diffuse collisions, i.e., the direction of post-collision velocities is distributed according to the Knudsen Cosine Law, and a fraction 1−ϑ undergoes specular reflection. From this assumption one obtains the value D=2−ϑϑDK for the self-diffusivity constant, where DK is a reference value corresponding to ϑ=1. In this paper we show that ϑ can be expressed in terms of micro- and macro-geometric parameters for a model consisting of hard spheres colliding elastically against a rigid surface with prescribed microgeometry.Our refinement of the MS theory is based on the observation that the classical surface scattering operator associated to the microgeometry has a canonical velocity space diffusion approximation by a generalized Legendre differential operator whose spectral theory is known explicitly. More specifically, starting from an explicit description of the effective channel surface microgeometry—a concept which incorporates both the actual surface microgeometry and the molecular radius—and using this operator approximation, we show that ϑ can be resolved into easily obtained geometric parameters, ϑ=λh/C, having the following interpretation: C is a macroscopic parameter determined by the shape of the channel cross-section; h is a parameter that precisely captures the degree of roughness of the effective microgeometry, and λ is a parameter that characterizes the overall curvature of the surface microgeometry independent of h. Thus ϑ is resolved as the quotient of microscopic (λh) over macroscopic (C) signature parameters of the channel geometry. The identity ϑ=λh/C holds up to higher order terms in the roughness parameter h, so our main result better applies to well polished, or low roughness, surfaces.

Исследование износостойких покрытий, нанесенных на образцы из конструкционной стали, применяемой для изготовления валов валопровода судов на подводных крыльях

Effective interaction of structural elements and materials from which they are made is one of the most important tasks in the design of parts and mechanisms of ship power plants. The operating experience of Meteor-type vessels has shown that the main cause of propeller shaft breakage and failure may be non-compliance with the technical requirements for the chemical-thermal processing of the shaft necks to the bearings size or poor-quality superficial coating. There has been made a comparative analysis of coating technologies, its results will significantly increase the cyclic wear resistance of the surface layer of the shaft necks of the hydrofoil ship shafting. The technologies of gas-plasma and gas-dynamic spraying, as well as electrospark alloying of the surface are considered. An instrumental assessment of the parameters of the applied protective coating quality is performed. Alloying materials for each of the methods of the surface hardening and modification are also presented. The scheme and design of the stand for testing the applied coatings for cyclic fatigue strength up to the moment of critical failure are given. The coatings deposited on the samples surfaces are studied to assess the surface microgeometry and microhardness. The samples are tested on the stand with a cyclic load at an induction motor shaft speed of 1800 rpm (30 rps). A bearing ball made of steel is used as an indenter. After testing, the focus of the coating destruction is assessed visually using a measuring and computing complex based on an optical microscope. As a result of the tests, it is revealed that the samples processed by the electrospark alloying method have the highest resistance to alternating cyclic effects, the lowest surface roughness and the highest microhardness.

An investigation into the effect of slip rate on the traction coefficient behaviour with a laboratory replication of a locomotive wheel rolling/sliding along a railway track

This paper investigates the effect of slip rate on the traction coefficient of the wheel/rail interface using a twin-disc machine under the replicated tribological and locomotive operating conditions. The traction coefficient decreases with increasing slip rate. The interface materials of the tested samples get less time to accumulate strain hardening, resulting in a lower increase in surface hardness under a faster slip rate. The running-in period is shorter under a higher slip rate, indicating that the surface micro-geometry of the interface materials reaches a steady state faster. The wear and traction coefficient outcomes of this research could be helpful in improving locomotive traction control systems, and in increasing the safety and maintenance efficiency of railway operations.

Influence of abutment macro- and micro-geometry on morphologic and morphometric features of peri-implant connective tissue.

The aim of the present human observational study is to provide morphologic and morphometric analysis of peri-implant connective tissue next to abutments with divergent or convergent macro-geometry and different surface micro-characteristics. Thirty patients were rehabilitated with single implants in the posterior area and one out of three different healing abutments with a one-stage technique: machined divergent abutment (DIV-MAC), machined convergent abutment (CONV-MAC) or convergent abutment with ultrathin threaded surface (CONV-UTM). At 3 months postimplant insertion, peri-implant soft tissue was harvested; the following outcomes were investigated: histomorphometry (vertical width of connective and epithelial components) as detected by histology and polarized light; and connective tissue vertical width and 3D organization as detected by synchrotron-based high-resolution phase-contrast-based tomography (PhC-μCT). Significant differences in connective tissue vertical dimension (aJE-AM) were found between DIV-MAC and both CONV-MAC and CONV-UTM, both by histology and PhC-μCT, with significantly higher values for the last two groups. Moreover, 2D histological analysis did not find significant differences in the junctional epithelium vertical dimension (PM-aJE). Importantly, PhC-μCT analysis revealed, at 3D level, significant greater amount and density of collagen bundles for CONV-UTM compared with the other two groups. Convergent abutment profiles, regardless of their surface micro-geometry, seem to favor axial development of peri-implant connective tissue. Moreover, ultrathin threaded surfaces seem associated with denser and greater connective tissue organization, which might improve peri-implant soft tissue seal.

SOLVING FUNCTIONAL-TECHNOLOGICAL PROBLEMS USING A NON-PARAMETRIC APPROACH FOR CONTROL OF MICROGEOMETRY OF THE SURFACES OF DETAILS

In the article considers the effect of surface roughness on the functioning of a specific mechanism. In case of proven dependence of the studied functional property of surface microgeometry, a process of optimization of the sought parameter is carried out, in which the methods of mathematical analysis and theoretic foundations of technology of appliance and mechanical engineering are used for the basis of the theoretical studies. As control parameters of the specified optimal microgeometry, deciding the given task, the so-called non-parametric criteria are used, namely graphical of certain surface-profile functions.

A Method for Mathematical Modeling of Hydrodynamic Friction of Plunger Pairs with Consideration of Microgeometry

The fuel injection system heavily relies on the high-pressure fuel pump, which plays a critical role in its overall performance. The fuel pump plunger is subjected to high levels of stress and experiences irregular lubrication during dynamic loads, causing premature wear. In the industrial sector, laser surface micro-texturing has been utilized to reduce friction and enhance anti-wear properties, and its positive impact has been supported by both theoretical and experimental evidence. This article presents a method for determining the hydromechanical characteristics of plunger pairs under conditions of hydrodynamic friction. The microgeometry of friction surfaces was taken into account through the cavitation effect of the lubricating fluid, described by the modified Reynolds equation. Software was developed according to the proposed method. The developed software can be used to analyze the contacting surfaces of plunger pairs and evaluate their tribotechnical characteristics based on the microgeometry parameters of the friction surfaces. The article also discusses the impact of the microgeometry parameters on the quality criteria of the hydromechanical characteristics of the plunger pairs. Computational examples are given for the analysis of contacting surfaces of plunger pairs separated by a lubrication layer. The technical characteristics are evaluated depending on the parameters of the microgeometry of the roughness of the friction surfaces. The influence of the microgeometry parameters on the quality criteria of the hydromechanical characteristics of the plunger pairs is presented.

Numerical simulation of the effect of surface microgeometry and residual stress on conformal contact fretting fatigue crack initiation behavior

AbstractConformal contact is a commonly presented contact form in assemblies. Non‐proportional loading is the main characteristics of conformal contact, which leads to prominent difficulty in revealing fretting crack behavior. In this paper, a finite element prediction model for Ti‐6Al‐4V pin‐hole contact fretting fatigue crack initiation was developed, which simultaneously considered the effect of fretting wear, surface roughness, surface skewness, surface kurtosis, and residual stress. The results show that phase differences of stress component, change in direction of principal stress, and high stress gradient are the main reasons for the initiation of fretting fatigue under conformal contact condition. The model based on the Fatemi–Socie (FS) parameter successfully predicted the location, orientation, and fatigue life of crack initiation, which agrees well with the experimental results. Additionally, machining‐induced residual stress can effectively inhibit mode I crack initiation at valleys. Moreover, ignoring the surface microgeometry characteristics reduces the prediction accuracy of the crack behavior.

Influence of the cutting blade shape on the technical hemp stalks slicing quality

The article presents the results of in-depth scientific research, including cutting of technical hemp stems with a blade of various shapes and interference of the cut surface by non-contact optical profilometry. Three-dimensional images and characteristic profilograms of the cut surfaces of stems depending on the shape of the cutting edge are obtained. The parameters of the microgeometry of the cut surface and the optimal profile of the cutting edge are determined.

Effects of Automotive Test Parameters on Dry Friction Fiber-Reinforced Clutch Facing Surface Microgeometry and Wear-Part 3 Tribological Parameter Correlations and Simulation of Thermo-Mechanical Tribological Contact Behavior.

Correlations among previously determined tribological properties, such as the coefficient of friction values, wear and surface roughness differences of hybrid composite dry friction clutch facings are revealed after pin-on-disk test apparatus examinations under three pv loads, where samples are cut from a reference, unused, and several differently aged and dimensioned, used-according to two different trends: dry friction fiber-reinforced hybrid composite clutch facings. In 'normal use' facings, increasing specific wear trend is detected as a function of activation energy according to a second-degree function, while a logarithmic trend line can be fitted to the values of the clutch killer facings, showing that even at low activation energy levels, significant (~3%) wear occurs. The specific wear rate also varies as a function of the radius of the friction facing, with the relative wear values measured on the working friction diameter being higher regardless of the usage trend. In terms of surface roughness variation measured in the radial direction, normal use facings show a varying roughness difference according to a third-degree function, while clutch killer facings follow a second-degree or logarithmic trend depending on the diameter (di or dw). From the statistical analysis of the steady-state, we find three different clutch engagement phase characterizing pv level pin-on-disk tribological test results for the specific wear of the clutch killer and normal use facings, and significantly different trend curves with three different sets of functions were obtained, showing that the wear intensity can be described as a function of the pv value and the friction diameter. In terms of radial direction surface roughness difference, the values of clutch killer and normal use samples can be described by three different sets of function showing the effects of the friction radius and pv.

Parametric analysis of the self-organization effect in the combined burnishing of holes in aluminum alloy billets

The process of self-organization of machined surfaces during combined burnishing of workpiece holes made of Д1Т aluminum alloy with a tool with a regular microgeometry of the working surface using a metal-cladding lubricant is studied. This treatment provides the wear-free Garkunov—Kragelsky effect during friction. Keywords: burnishing, hole, regular relief, metal-cladding lubricant, wear-free effect, friction. nadezhdachi@yandex.ru, bekaev@list.ru, drsc1@yandex.ru, ld-gim@yandex.ru

Метод математического моделирования гидродинамического трения плунжерных пар с учетом микрогеометрии

The fuel injection system strongly relies on a high pressure fuel pump which is essential for its overall performance. The fuel pump plunger is subject to high loads and irregular lubrication under dynamic loads, which leads to its premature wear. The industrial sector uses laser surface micro-texturing to reduce friction and improve anti-wear properties. Its positive effects are supported by both theoretical and experimental data. The paper presents a method for determining the hydromechanical characteristics of plunger pairs during hydrodynamic friction. The microgeometry of friction surfaces was taken into account due to the lubricating fluid cavitation effect described by the modified Reynolds equation. The proposed method can be applied to develop the software to analyze the contacting surfaces of plunger pairs and evaluate their tribological characteristics based on the microgeometry parameters of friction surfaces. The paper also studies the influence of microgeometry parameters on the quality criteria of the hydromechanical characteristics of plunger pairs. It gives the calculated examples of analyzing the contacting surfaces of plunger pairs separated by a lubricant layer. The technical specifications are assessed depending on the microgeometry parameters of the friction surface roughness.