Wyniki wyszukiwania - Biblioteka Nauki

1

Mechanical behavior of wheel steels with solid solution and precipitation hardening

100%

Kulyk V. V. , Shipitsyn S. Y. , Ostash O. P. , Duriagina Z. A. , Vira V. V.

Archives of Materials Science and Engineering

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2019

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tom Vol. 95, nr 2

49--54

EN

Purpose: The aim of the proposed research is to investigate operational properties of a wheel steel treated with simultaneous solid solution and precipitation hardening at various carbon content, in comparison with the standard wheel grade T steel. Design/methodology/approach: The mechanical behaviour of wheel steels with increased content of silicon, manganese, vanadium, and nitrogen at various carbon content has been investigated and compared to that of the standard high-strength wheel grade T steel. The steels were undergo thermal treatment due to austenitic heating up to a temperature of 950.C with cooling down in water to 550.C followed by intense blowing of blanks in the air. After that, a tempering was performed at a temperature in the range of 450-650.C. Static strength (UTS), relative elongation (TEL), impact toughness tests (KCV) were determined on standard specimens. The characteristics of Mode I fatigue crack growth resistance of steel were determined on the basis of fatigue macrocrack growth rate diagrams da/dN–ΔKI, obtained by the standard method on compact specimens with the thickness of 10 mm at a frequency of 10-15 Hz and the stress ratio R = 0.1 and R = 0.5 of the loading cycle. The characteristics of Mode II fatigue crack growth resistance were determined on the basis of da/dN–ΔKII diagrams, obtained earlier method on edge notched specimens with the thickness 3.2 mm at a frequency of 10-15 Hz and R = -1 taking account of the crack face friction. Rolling contact fatigue testing was carried out on the model specimens. Findings: The regularities of the change of mechanical characteristics of the high-strength wheel steel with simultaneous solid solution and precipitation hardening at lowered carbon content under static, impact and cyclic loading are studied. Research limitations/implications: The results obtained using laboratory samples should be checked during a real railway wheels investigation. Practical implications: The investigated steel with simultaneous solid solution and precipitation hardening provides high wear resistance of the tread surface and damage resistance determined on the model wheels. Originality/value: A steel with solid solution hardening due to increased content of silicon (up to 0.7%) and manganese (up to 0.8%) and also with precipitation hardening (at optimal content of vanadium and nitrogen [V‧N]‧104 = 28.9%) at lowered carbon content (0.52) possesses high strength and fatigue fracture toughness in cases of Mode I and Mode II loading, causing better combination of wear and damage resistances of the tread surface of the model wheels, as compared to corresponding parameters for grade T steel.

2

Investigation of structural-geometric parameters and elemental composition of spherical VT20 alloy powders

100%

Duriagina Z. A. , Filimonov O. S. , Kulyk V. V. , Lemishka I. A. , Kuziola R.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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tom Vol. 95, nr 2

49--56

EN

Purpose: Identification of structural-geometrical parameters, technological properties and elemental composition of spherical powders in a wide fraction range with respect to the VT20 alloy has been carried out. This is important for evaluating the optimum filling of a given volume by mixture of powders of different fractions during 3D printing. Design/methodology/approach: During the investigation of spherical Ti-alloy powders, a comprehensive approach was performed using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Dynamic Light Scattering (DLS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The surface morphology of the powders was studied on a Tuescan Vega 3 Scanning Electron Microscope. Using the Quantax energy dispersive spectrometer, element distribution maps were obtained and histograms of element distribution in the investigated powders were constructed. ICP-MS analysis was performed to clarify the elemental composition. DLS analysis using Malvern's Zetasizer Nano-ZS equipment allowed us to determine the functional parameters (hydrodynamic radius – Rh, zeta potential – z and specific conductivity) of particles of titanium alloy powder that indirectly indicate a tendency to form conglomerates. Findings: According to the microscopic examinations, the VT20 alloy powder consists of globular-shaped particles with the lamellar traces on their surfaces. The uniformity of the chemical element distribution within each fraction of the investigated powders was confirmed by EDS, and the full conformity of the powder fractions with the elemental composition of the VT20 alloy was confirmed by ICP-MS. The DLS method allowed to establish that the formation of conglomerates would not occur within the studied fractions of the VT20 alloy powder. Research limitations/implications: The use of high sensitive investigation methods gives understanding of the mechanisms of fine structure formation and possibility to control the processes of powder coagulation in the stage of electrostatic interactions. Practical implications: The obtained results can be used for the formation of fine spherical particles of the powder, but at the same time, these technologies can be extended for the particles of non-spherical shape. Originality/value: The DLS method allowed to establish that the formation of conglomerates would not occur within the studied fractions of the VT20 alloy powder. This, in turn, will improve powder melting during 3D printing. The measured zeta potential values allowed us to reveal mechanisms of fine structure formation and to control the processes of powder coagulation in the stage of electrostatic interactions.

3

The effect of water vapor containing hydrogenous atmospheres on the micro-structure and tendency to brittle fracture of anode materials of YSZ–NiO(Ni) system

100%

Kulyk V. V. , Vasyliv B. D. , Duriagina Z. A. , Kovbasiuk T. M. , Lemishka I. A.

Archives of Materials Science and Engineering

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2021

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tom Vol. 108, nr 2

49--67

EN

Purpose: The purpose of this work is to estimate the tendency to brittle fracture of the YSZ–NiO(Ni) anode cermet in a hydrogenous environment with various concentrations of water vapor. Design/methodology/approach: YSZ–NiO ceramic plates were fabricated by sintering in an argon atmosphere. The treatment of material was performed in a hydrogenous environment with various concentrations of water vapor. The strength test was performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope (SEM) Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The porosity of the materials was investigated by analysing the SEM micrographs using the image processing technique. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, physical and mechanical characteristics of YSZ–NiO(Ni) material for solid oxide fuel cell (SOFC) anodes of different preconditioning modes aged under various partial pressures of water vapor in a hydrogenous environment are found. Research limitations/implications: To study the actual behaviour of the YSZ–NiO(Ni) anode material in the operating environment, it is necessary to evaluate its strength, Young’s modulus, microhardness, and fracture toughness by changing with a certain step the partial pressure of water vapor in the whole range noted in this work.Practical implications: Based on the developed approach to assessing the propensity to brittle fracture of the formed cermet microstructure, it is possible to obtain an anode material that will provide the necessary functional properties of a SOFC. Originality/value: An approach to estimating the propensity to brittle fracture of a formed cermet structure is proposed based on the microhardness and fracture toughness characteristics obtained by the Vickers indentation method.

4

The joint effect of vanadium and nitrogen on the mechanical behavior of railroad wheels steel

100%

Kulyk V. V. , Shipitsyn S. Y. , Ostash O. P. , Duriagina Z. A. , Vira V. V.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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tom Vol. 89, nr 2

56--63

EN

Purpose: The aim of the proposed research is to investigate the regularities of the microstructure change, fracture micromechanism and mechanical service characteristics of the high-strength wheel steel with a lowered carbon content under static, impact and cyclic loading depending on the total content of vanadium and nitrogen and also the steel heat treatment modes. Design/methodology/approach: Alloying with vanadium was carried out in the range of 0.09-0.23% and nitrogen in the range of 0.006-0.018%. All steels were heat treated by normalizing and subsequent tempering at different temperatures in the range of 450-650°C. Steels microstructure was investigated by the optical metallography methods on the microscope EPITIP-2 (Carl Zeiss Jena). Scanning electron microscope Zeiss-EVO40XVP was also used for microstructural and microfractography investigations. Static strength (UTS), relative elongation (TEL), impact toughness tests (KCV) and fatigue crack growth resistance characteristics (fatigue threshold ΔKth, cyclic fatigue fracture toughness ΔKfc) were determined on standard specimens. Rolling contact fatigue testing was carried out on the model specimens. Findings: The regularities of the change of microstructure, fracture micromechanism and mechanical characteristics of the high-strength wheel steel with a lowered carbon content under static, impact and cyclic loading depending on the total content of vanadium and nitrogen and also the steel heat treatment modes are studied. Research limitations/implications: The results obtained on laboratory samples should be tested during a real railway wheels investigation. Practical implications: The steel with the optimal parameter [V∙N]∙104 = 22.1% provides high tread surface damaging resistance established on the model wheels. Originality/value: It was established that after normalization at 950°C and tempering at 550°C the increase of ultimate strength UTS and cyclic fracture toughness ΔKfc by 4% and 19%, respectively; impact toughness at room (KCV+20) and low temperature (KCV-40) in 1.5 and 3.3 times, respectively, when parameter [V∙N]∙104 changes from 7.8 to 22.1% and carbon content from 0.63 to 0.57%.

5

Influence of 65G steel microstructure on crack faces friction factor under mode II fatigue fracture

100%

Ivanytskyj Y. L. , Lenkovskiy T. M. , Molkov Y. V. , Kulyk V. V. , Duriagina Z. A.

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tom Vol. 82, nr 2

49--56

EN

Purpose: The aim of the paper is to evaluate the dependence of microstructure parameters, strength and plasticity of steel on crack faces friction factor. Design/methodology/approach: The specimens for the investigation were cut out from the 10 mm thick hot-rolled plate of 65G steel used as a model material for fatigue and durability testing of whole-rolled railway wheels. The mechanical characteristics of the steel were determined according to the state standard using cylindrical specimens of diameter 5 mm and effective length 50 mm. The specimens were heat-treated at the mentioned conditions. Fatigue testing under mode II loading was carried out on a special rigid loading machine in the standard laboratory conditions at symmetric sinusoidal cycle with a frequency of 12 Hz in the range of fatigue crack growth rates da/dN = 5∙10⁻⁸…5∙10⁻⁷ m/cycle until its reaches relative length l/b ≥ 0.8. The obtained microsections were investigated using the optical metallographic microscope Neophot 9 equipped with a digital camera Nikon D50 and electronic scanning microscope Zeiss EVO 40XVP. Hardness of the specimens with different microstructure was determined using durometer TK-2. The crack faces friction factor was determined using original device for fractured surfaces sliding under certain compression force realization. Findings: The dependences of microstructure parameters, strength and plasticity of steel on crack faces friction factor are obtained. Research limitations/implications: The investigation of the influence of microstructure parameters, strength and plasticity of real wheel steels on crack faces friction factor at the mode II fatigue crack growth will be carried out. Practical implications: The value of crack faces friction factor have strong impact on stress intensity at the crack tip and must be taken into account at crack growth rates curves plotting. Originality/value: Mode II fatigue crack faces friction factor of steel is firstly experimentally determined.

6

Finite elements analysis of the side grooved I-beam specimen for mode II fatigue crack growth rates determination

86%

Lenkovskiy T. M. , Kulyk V. V. , Duriagina Z. A. , Dzyubyk L. V. , Vira V. V. , Dzyubyk A. R. , Tepla T. L.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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tom Vol. 86, nr 2

70--77

EN

Purpose: Carefully investigate the stress-strain state of the side grooved I-beam specimen with edge crack and determine the effect of crack length and crack faces friction on stress intensity factor at transverse shear. Design/methodology/approach: The finite element method was used to estimate the stress-strain state of I-beam specimen at transverse shear. For this purpose, a fullscale, three-dimensional model of the specimen was created, which precisely reproduces its geometry and fatigue crack faces contact. For the correct reproduction of the stress singularity at the crack tip, a special sub-model was used, which has been tested earlier in solving similar problems of fracture mechanics. In order to improve the accuracy of the calculations, for crack plane and cross-section of the specimen on the crack extension modeling, an algorithm for changing the crack length without changing the total number of elements in the model was developed and applied. Young's modulus and Poisson's ratio of structural steels were specified for the model material. The static loading of the model was realized assuming small scale yielding condition. The stress intensity factor was found through the displacement of nodes in the prismatic elements adjacent to the plane and the front of the crack. Findings: Mathematical dependences, which show an increase of stress intensity factor in the I-beam specimen with an increase in the crack length, and its decrease with an increase of crack faces friction factor at transverse shear, were established. The results are compared with the partial cases known from the literature and their good convergence was shown. Research limitations/implications: By analyzing the obtained graphical dependences, it is established that for relative crack lengths less than 0.4 there is a significant influence of the initial notch on the stress-strain state of the specimen, and for the lengths greater than 0.9 an influence of constrained gripping part took place. For this reason, all subsequent calculations were carried out in the range of relative crack length from 0.4 to 0.9, which represents the applicability range of the final calculation formula. Increasing of the crack faces friction factor from 0 to 1 monotonically reduces the stress at the crack tip. For a short crack, this effect is 1.5 times greater than for a long one, which is reflected by the calculation formula. Practical implications: Using the proposed calculation formula, one can calculate the stress intensity factor in the I-beam specimen, and to determine the crack growth resistance characteristics of structural steels at transverse shear. Originality/value: A new, easy-to-use in engineering calculations formula is proposed for stress intensity factor determination in the I-beam specimen at transverse shear. The formula takes into account crack faces friction for various crack lengths.

7

Assessing surface fatigue crack growth in railway wheelset axle

86%

Rudavskyi D. V. , Kaniuk Y. I. , Duriagina Z. A. , Kulyk V. V. , Shefer M. S. , Dolinska I. Y.

Archives of Materials Science and Engineering

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2020

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tom Vol. 106, nr 2

59--67

EN

Purpose: The aim of the proposed research is to create a calculation model of surface fatigue crack growth at the axle of railway wheelset working under operational loads. Design/methodology/approach: The energy approach of the fracture mechanics was used to formulate the calculation model of fatigue crack propagation at the wheelset axle surface. The method of least squares was used to determine the investigated material mechanical constants that the kinetic equations of the calculation model contain. The system of differential equations of crack growth kinetics was solved numerically using the Runge-Kutta method. Findings: On the basis of the energy approach of the fracture mechanics the calculation model of fatigue macrocrack growth in three-dimensional elastic-plastic body in case of a mixed-mode I+II+III macromechanism of fracture has been built. On the basis of the created calculation model, the kinetics of the growth of fatigue cracks was investigated both in the middle part of the wheelset axle and in the axle journal. Research limitations/implications: The results obtained on laboratory specimens should be tested during a real railway wheelset axle investigation. Practical implications: The created calculation model can be used in practice to formulate method of residual lifetime estimation of railway wheelset axle. Originality/value: It was shown, that surface crack kinetics depends not only on the crack initial area but also significantly depends on the crack edge geometry and comparatively small crack-like defects at the wheelset axle surface can reach critical sizes in comparatively short run. It has been found that mechanical shear stresses caused by the weight of the loaded railway wagon in the cross section of the wheelset axle journal can significantly accelerate the growth of the transverse fatigue crack at the axle surface, reducing the period of crack subcritical growth by about 20%.

8

The character of the structure formation of model alloys of the Fe-Cr-(Zr, Zr-B) system synthesized by powder metallurgy

86%

Duriagina Z. A. , Romanyshyn M. R. , Kulyk V. V. , Kovbasiuk T. M. , Trostianchyn A. M. , Lemishka I. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2020

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tom Vol. 100, nr 2

49--57

EN

Purpose: The purpose of the work is to synthesize and investigate the character of structure formation, phase composition and properties of model alloys Fe75Cr25, Fe70Cr25Zr5, and Fe69Cr25Zr5B1. Design/methodology/approach: Model alloys are created using traditional powder metallurgy approaches. The sintering process was carried out in an electric arc furnace with a tungsten cathode in a purified argon atmosphere under a pressure of 6·104 Pa on a water cooled copper anode. Annealing of sintered alloys was carried out at a temperature of 800°C for 3 h in an electrocorundum tube. The XRD analysis was performed on diffractometers DRON-3.0M and DRON-4.0M. Microstructure study and phase identification were performed on a REMMA-102-02 scanning electron microscope. The microhardness was measured on a PMT-3M microhardness meter. Findings: When alloying a model alloy of the Fe-Cr system with zirconium in an amount of up to 5%, it is possible to obtain a microstructure of a composite type consisting of a mechanical mixture of a basic Fe2(Cr) solid solution, solid solutions based on Laves phases and dispersive precipitates of these phases of Fe2Zr and FeCrZr compositions. In alloys of such systems or in coatings formed based on such systems, an increase in hardness and wear resistance and creep resistance at a temperature about 800°C will be reached. Research limitations/implications: The obtained results were verified during laser doping with powder mixtures of appropriate composition on stainless steels of ferrite and ferrite-martensitic classes. Practical implications: The character of the structure formation of model alloys and the determined phase transformations in the Fe-Cr, Fe-Cr-Zr, and Fe-Cr-B-Zr systems can be used to improve the chemical composition of alloying plasters during the formation of ferrite and ferrite-martensitic stainless steel coatings. Originality/value: The model alloys were synthesized and their phase composition and microstructure were studied; also, their microhardness was measured. The influence of the chemical composition of the studied materials on the character of structure formation and their properties was analysed.

9

Effects of yttria content and sintering temperature on the microstructure and tendency to brittle fracture of yttria-stabilized zirconia

86%

Kulyk V. V. , Duriagina Z. A. , Vasyliv B. D. , Vavrukh V. I. , Lyutyy P. Y. , Kovbasiuk T. M. , Holovchuk M. Y.

Archives of Materials Science and Engineering

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2021

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tom Vol. 109, nr 2

65--79

EN

Purpose: The purpose of this work is to evaluate the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria, based on a study of changes in the microstructure, phase composition, and fracture micromechanisms. Design/methodology/approach: The series of 3YSZ, 4YSZ, and 5YSZ ceramic specimens were sintered in an argon atmosphere. Three sintering temperatures were used for each series: 1450°C, 1500°C, and 1550°C. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The fracture toughness of the material was estimated using both the Vickers indentation method and a single-edge notch beam (SENB) test performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, and mechanical characteristics of YSZ ceramic materials of different chemical and phase compositions sintered in a temperature range of 1450°C to 1550°C are found. Research limitations/implications: To study the actual behaviour of YSZ ceramic materials under operating conditions, it is necessary to evaluate their Young’s moduli, strength, microhardness, and fracture toughness in an operating environment of the corresponding parameters (temperature, pressure, etc.).Practical implications: Based on the developed approach to estimating the propensity to brittle fracture of the formed YSZ ceramic microstructure, it is possible to obtain YSZ ceramic material that will provide the necessary physical and mechanical properties of a wide variety of precision ceramic products. Originality/value: An approach to estimating the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria is proposed based on two methods of evaluating crack growth resistance of materials, namely, the Vickers indentation method and SENB method.

10

Determination of conditions for loss of bearing capacity of underground ammonia pipelines based on the monitoring data and flexible search algorithms

86%

Mysiuk R. V. , Yuzevych V. M. , Yasinskyi M. F. , Kniaz S. V. , Duriagina Z. A. , Kulyk V. V.

Archives of Materials Science and Engineering

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2022

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tom Vol. 115, nr 1

13--20

EN

Purpose: The study aims to diagnose the corrosion current density in the coating defect on the outer surface of the ammonia pipe depending on the distance to the pumping station, taking into account the interaction of media at the soil-steel interface and using modern graphical data visualization technologies and approaches to model such a system. Design/methodology/approach: The use of an automated system for monitoring defects in underground metallic components of structures, in particular in ammonia pipelines, is proposed. The use of the information processing approach opens additional opportunities in solving the problem of defect detection. Temperature and pressure indicators in the pipeline play an important role because these parameters must be taken into account in the ammonia pipeline for safe transportation. The analysis of diagnostic signs on the outer surface of the underground metallic ammonia pipeline is carried out taking into account temperature changes and corrosion currents. The parameters and relations of the mathematical model for the description of the influence of thermal processes and mechanical loading in the vicinity of pumping stations on the corresponding corrosion currents in the metal of the ammonia pipeline are offered. Findings: The paper evaluates the corrosion current density in the coating defect on the metal surface depending on the distance to the pumping station and the relationship between the corrosion current density and the characteristics of the temperature field at a distance L = 0…20 km from the pumping station. The relative density of corrosion current is also compared with the energy characteristics of the surface layers at a distance L = 0…20 km from the pumping station. An information system using cloud technologies for data processing and visualization has been developed, which simplifies the process of data analysis regarding corrosion currents on the metal surface of an ammonia pipeline. Research limitations/implications: The study was conducted for the section from the pumping station to the pipeline directly on a relatively small data set. Practical implications: The use of client-server architecture has become very popular, thanks to which monitoring can be carried out in any corner of the planet, using Internet data transmission protocols. At the same time, cloud technologies allow you to deploy such software on remote physical computers. The use of the Amazon Web Service cloud environment as a common tool for working with data and the ability to use ready-made extensions is proposed. Also, this cloud technology simplifies the procedure of public and secure access to the collected information for further analysis. Originality/value: Use of cloud environments and databases to monitor ammonia pipeline defects for correct resource assessment.

11

Determination of the best microstructure and titanium alloy powders properties using neural network

86%

Duriagina Z. A. , Tkachenko R. O. , Trostianchyn A. M. , Lemishka I. A. , Kovalchuk A. M. , Kulyk V. V. , Kovbasyuk T. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2018

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tom Vol. 87, nr 1

25--31

EN

Purpose: Create a software product using a probabilistic neural network (PNN) and database based on experimental research of titanium alloys to definition of the best microstructure and properties of aerospace components. Design/methodology/approach: The database creation process for artificial neural network training was preceded by the investigation of the granulometric composition of the titanium powder alloys, study of microstructure, phase composition and evaluation of micromechanical properties of these alloys by the method of material plasticity estimation in the conditions of hard pyramidal indenters application. A granulometric analysis was done using a special complex of materials science for the images analysis ImageJ. Metallographic investigations of the powder structure morphology were carried out on the scanning electron microscope EVO 40XVP. Specimens for micromechanical testing were obtained by overlaying the titanium alloy powders on the substrate made of the material close to chemical composition. Substrates were prepared by pressing the powder mixture under the load of 400 MPa and following sintering at 1300°C for 1 hour. Overlaying was performed by an electron gun ELA-6 (beam current – 16 mA). Findings: According to the modelling results, a threshold of the PNN accuracy was established to be over 80%. A high level of experimental data reproduction allows us a full or partial replacement of a number of experimental investigations by neural network modelling, noticeably decreasing, in this case, the cost of the material creation possessing the preset properties with preserved quality. It is expected that this software can be used for solving other problems in materials science too. Research limitations/implications: The accuracy of the PNN algorithm depends on the number of input parameters obtained experimentally and forms a database for the training of the system. For our case, the amount of input data is limited. Practical implications: Previously trained system based on the PNN algorithm will reduce the number of experiments that significantly reduce costs and time to study. Originality/value: A software product on the basis of the PNN network was developed. The training sample was built based on a series of laboratory studies granulometric composition of the titanium powder alloys, study of microstructure, phase composition and evaluation of micromechanical properties of powder materials. The proposed approach allows us to determine the best properties of the investigated material for the design of aerospace components.

12

Mode I and mode II fatigue crack growth resistance characteristics of high tempered 65G steel

86%

Lenkovskiy T. M. , Kulyk V. V. , Duriagina Z. A. , Kovalchuk R. A. , Topilnytskyy V. H. , Vira V. V. , Tepla T. L.

Archives of Materials Science and Engineering

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2017

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tom Vol. 84, nr 1

34--41

EN

Purpose: To investigate the fatigue crack growth at normal tension and transverse shear of 65G steel with the high tempered martensite microstructure and to build an appropriate fatigue crack growth rate curves. To determine the main and auxiliary fatigue crack growth resistance characteristics, which are necessary for machine parts life-time estimation at rolling contact fatigue conditions. Design/methodology/approach: For determination of fatigue crack growth resistance at normal tension a standard compact specimens with edge crack were tested using a hydraulic testing machine and fatigue testing at transverse shear were performed on the I-beam specimens with the edge longitudinal crack using the original testing setup. For crack growth measurement an optical cathetometer B-630 was used. The crack growth rate V was calculated as crack length increment during loading cycles. The stress intensity factor range K was determined by dependence "K = (1 – R)Kmax accordingly to the standard test methods. To establish crack faces friction factor at transverse shear fragments of fractured beam specimen containing crack faces were cut out and tested as a friction pair according to Amontons Coulomb's law. On the base of test results the fatigue crack growth rate curves in logarithmic coordinates "K vs. V were built. These graphical dependencies for normal tension and transverse shear were used for determination of fatigue crack growth resistance characteristics: fatigue threshold "Kth, fracture toughness "Kfc, "K1-2 and "K2-3 which indicates the beginning and the end of middle-amplitude region of curve, "K*, parameters C and n of Paris’s equation. Metallographic and fractographic analyses were performed on the scanning electronic microscope Zeiss EVO 40XVP. Findings: Empirical dependences of the stress intensity factor range on fatigue crack growth rate at normal tension and transverse shear of 65G steel with the high tempered martensite microstructure are obtained. Based on these graphical dependencies the fatigue thresholds and fracture toughness as well as the parameters of Paris’s equation are determined. Research limitations/implications: The fatigue crack growth on 65G steel under low-, medium- and high-amplitude cyclic loading at normal tension and transverse shear was investigated. The fatigue crack growth rate values for a wide range of stress intensity factor are estimated. On the base of fractographical analysis the features of fracture of high tempered martensite in 65G steel at transverse shear are studied. It is shown that the transverse shear crack faces friction factor for high tempered martensite structure is less than for low tempered martensite. Practical implications: Using the fatigue crack growth resistance characteristics of 65G steel at normal tension and transverse shear and related fatigue crack growth rate curves it is possible to predict the life-time of machine parts made of steels with high tempered martensite structure, working at rolling contact fatigue conditions. Originality/value: Complete fatigue crack growth rate curves of 65G steel with tempered martensite structure at normal tension and transverse shear are built and the fatigue crack growth resistance characteristics for both modes of fracture are determined for the first time.

13

Microstructure and electrochemical properties of the vanadium alloys after low-temperature nitrogen plasma treatment

86%

Duriagina Z. A. , Ryzhak D. D. , Kulyk V. V. , Tepla T. L. , Lemishka I. A. , Bohun L. I.

Archives of Materials Science and Engineering

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2020

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tom Vol. 102, nr 1

5--12

EN

Purpose: The proposed research aims to determine the expediency of surface treatment of vanadium alloys of V-Cr and V-Ti systems due to irradiation of their surfaces with low- temperature nitrogen plasma using plasma torch NO-01. Design/methodology/approach: The investigation of microstructure and X-ray fluorescence analysis (XRF) of the samples were performed using an electron microscope TESCAN Vega3. The microhardness (Vickers hardness) of the samples was measured before and after surface treatment. The study of corrosive properties of the surface layers was performed by an electrochemical impedance spectroscopy (EIS) method. Corrosion damages were identified using impedance dependences. Findings: The microstructure of the surface layers of the V-8Ti, V-15Cr, and V-35Cr alloys in the initial state and after plasma treatment have been investigated. The chemical composition of the surface layers is determined and comparative measurements of the microhardness of these alloys are carried out. Corrosion-electrochemical properties (corrosion potentials, electrochemical impedance spectroscopy and constructed potential-dynamic polarization curves) of investigated alloys after treatment with nitrogen plasma are evaluated. Research limitations/implications: The results obtained using laboratory samples should be checked at the conditions of power equipment operation. Practical implications: This treatment has advantages over other methods of surface engineering since it provides strong surface plastic deformation and the possibility of formation of secondary phases resulting in increases in surface hardness and corrosion resistance. Originality/value: Vanadium alloys have significant advantages over other structural materials due to their high thermal conductivity and swelling resistance, high strength and plasticity up to temperatures of 700-800°C, and good weldability.

14

Relationships between the fatigue crack growth resistance characteristics of a steel and the tread surface damage of railway wheel

86%

Ostash O. P. , Kulyk V. V. , Lenkovskiy T. M. , Duriagina Z. A. , Vira V. V. , Tepla T. L.

Archives of Materials Science and Engineering

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2018

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tom Vol. 90, nr 2

49--55

EN

Purpose: The aim of the proposed research is to establish experimentally the relation between damaging of the tread surface of model wheels and the characteristics of fatigue crack growth resistance of wheel steels AKh th AKh th AKh fc AKh fc), depending on its microstructure. Design/methodology/approach: Characteristics of the fatigue crack growth resistance have been determined on the specimens cut out from the hot rolled plate of thickness 10 mm of the steel which is an analogue of railway wheel steels. To obtain different steel microstructures and its strength level, test specimens were quenched (820°C, in oil) and then tempered at 400°C, 500°C, and 600°C for 2 h. The characteristics of Mode I fatigue crack growth resistance of steel were determined on the basis of fatigue macrocrack growth rate diagrams da/dN-AK, obtained by the standard method on compact specimens with the thickness of 10 mm at a frequency of 10-15 Hz and the stress ratio R = 0.1 of the loading cycle. The characteristics of Mode II fatigue crack growth resistance were determined on the basis of da/dN-AKH diagrams, obtained by authors method on edge notched specimens with the thickness 3.2 mm at a frequency of 10-15 Hz and R = –1 taking account of the crack face friction. The hardness was measured with a TK-2 hardness meter. Zeiss-EVO40XVP scanning electron microscope was used for microstructural investigations. Rolling contact fatigue testing was carried out on the model specimens of a wheel of thickness 8 mm and diameter 40 mm in contact with a rail of length 220 mm, width 8 mm and height 16 mm. Wheels were manufactured form the above-described steel after different treatment modes. Rails were cut out from a head the full-scale rail of hardness 46 HRC. The damaging was assessed by a ratio of the area with gaps formed by pitting and spalling to the general area of the wheel tread surface using a special stand. Findings: The growth of the damage of the tread surface of the model wheels correlates uniquely with the decrease of the cyclic fracture toughness of the wheel steel AKh fc and AKh fc, determined at Mode I and Mode II fracture mechanisms. These characteristics of the wheel steel can be considered as the determining parameter of this process, in contrast to the fatigue thresholds AKh th and AKh th. Research limitations/implications: Investigations were conducted on model wheels that simulate the damage of real railway wheels tread surface. Practical implications: A relationship between the damage of tread surface of railway wheels and the strength level of wheel steels is determined. Originality/value: The damage of the tread surface of the model wheels during the rolling contact fatigue of the pair wheel-rail increases with the growth of the strength (hardness) of the wheel steel, which corresponds to the statistical data of the operation of the real railway wheels. Research limitations/implications: Investigations were; conducted on model wheels that simulate the damage of real railway wheels tread surface. Practical implications: A relationship between the damage of tread surface of railway wheels and the strength level of wheel steels is determined. Originality/value: The damage of the tread surface of the model wheels during the rolling) contact fatigue; of the pair wheel-rail increases with the growth of the strength (hardness) of the wheel steel, which corresponds to the statistical data of the operation of the real railway wheels.

15

The effect of the modification by ultrafine silicon carbide powder on the structure and properties of the Al-Si alloy

86%

Kovbasiuk T. M. , Selivorstov V. Y. , Dotsenko Y. V. , Duriagina Z. A. , Kulyk V. V. , Kasai O. M. , Voitovych V. V.

Archives of Materials Science and Engineering

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2020

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tom Vol. 101, nr 2

57--62

EN

Purpose: Determine the possibility of modifying aluminium alloys of the Al-Si system with an ultrafine SiC modifier with a particie size of 3-5 pm. Design/methodology/approach: Processing of the Al-Si alloy was carried out by introducing an ultrafine modifier in the amount of 0.1, 0.2, or 0.3 wt.%. Silicon carbide (SiC) with a particle size in the range of 3-5 pm was used as a modifier. To study the microstructure of the formed surface layers, a metallographic analysis was performed according to the standard method on a microscope MIKPOTEX® MMT-14C using TopView software. Microhardness studies of the samples were carried out on a Vickers microhardness tester NOVOTEST TC-MKV1. The microstructure of castings of the AlSi12 grade was studied at magnification from 100 to 400 times on the horizontal and vertical surfaces of the samples after etching with a 2% NaOH aqueous solution. Findings: Aluminium cast alloy of Al-Si system has been synthesized with the addition of 0.1, 0.2, and 0.3 wt.% ultrafine SiC modifier. It was found that the modification of the AlSi12 alloy by SiC particles of 3-5 pm in size led to an improvement of its microstructure due to the reduction of the volume fraction of micropores and primary Si crystals. It was shown that the AlSi12 aluminium alloy due to the modification by 0.2 wt.% SiC has the best micromechanical properties and macrostructure density. Research limitations/implications: The obtained research results are relevant for cast specimens of the indicated sizes and shapes. The studies did not take into account the influence of the scale factor of the castings. Practical implications: The developed modification technology was recommended for use in the conditions of the foundry "Dnipropetrovsk Aggregate Plant" (Dnipro, Ukraine). Originality/value: The technology of AlSi12 alloy modification of ultrafine SIC modifier with a particle size of 3-5 pm was used for the first time.

16

Study of structure and morphology of surface layers formed on TRIP steel by the femtosecond laser treatment

86%

Duriagina Z. A. , Tepla T. L. , Kulyk V. V. , Kosarevych R. Y. , Vira V. V. , Semeniuk O. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2019

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tom Vol. 93, nr 1-2

5--19

EN

Purpose: The purpose of the work is to demonstrate the possibility of using a femtosecond laser for forming surface layers with an adjustable microstructure on the surface of TRIP steel 03X13AG19, and processing the obtained images using digital complexes. Design/methodology/approach: A laser treatment of TRIP steel (03X13AG19) with pulses of femtosecond duration was carried out in a melting mode. The source of the radiation is a femtosecond titanium-sapphire Ti:Al2O3 complex consisting of a predefining femtosecond generator “Mira Optima 900-F” and regenerative amplifier Legend F-1K-HE. Peculiarities of the surface structure of irradiated samples were studied using a Solver P47-PRO atomic force microscope. The structural-geometric parameters of the surface of the investigated steel treated with the femtosecond laser were determined using the software package Nova 1.0.26.1443 and the functions of the Image Analysis. Microstructural analysis was performed using a raster electron microscope JSM 6700F and a METAM-1P microscope. In this work, the digitization of images of microstructures obtained as a result of surface irradiation by highly concentrated energy streams of femtosecond duration has been carried out. The analysis of the surface structure of laser-structured materials was carried out using a metallographic complex with the software ImProcQCV. Findings: It has been revealed that the predetermined change of the laser treatment mode changes the microrelief and the shape and size of the fragments of the surface structure of the investigated steel. The use of digital image processing allowed to generalize the morphological features of the surface structure, to assess in detail the character of the microrelief, and to monitor under in-situ mode the structure and properties of the surface of the material being studied. Research limitations/implications: The obtained research results can be applied to stainless steels of various structural classes. Practical implications: Surface digitization significantly reduces the time for research, improves the quality and accuracy of the data obtained, makes it possible to conduct in-situ researches with the further implementation of the results using the Internet of Things technologies. Originality/value: A comprehensive approach is proposed for the estimation of parameters of laser-induced periodic surface structures (LIPSS) using a metallographic complex with the software ImProcQCV.

17

The effect of electrolyte composition on the plasma electrolyte oxidation and phase composition of oxide ceramic coatings formed on 2024 aluminium alloy

86%

Posuvailo V. M. , Kulyk V. V. , Duriagina Z. A. , Koval’chuck I. V. , Student M. M. , Vasyliv B. D.

Archives of Materials Science and Engineering

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2020

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tom Vol. 105, nr 2

49--55

EN

Purpose: Purpose of this work is to analyse the process of synthesis of oxide ceramic coatings in plasma electrolytes on 2024 aluminium alloy and to form an electrolyte which allows to reduce energy consumption for the coating formation. Design/methodology/approach: The oxide ceramic coatings were synthesized on 2024 aluminium alloy. The coatings were formed by the alternate application of anode and cathode pulses to the sample. X-ray diffraction analysis of coatings was performed on a DRON-3.0 X-ray diffractometer using CuKa radiation. The thickness of the coatings was determined using a CHY TG-05 thickness gauge. The porosity of the coatings was investigated by analysing the micrographs of the plasma electrolyte oxidation (PEO) coatings obtained on a scanning electron microscope at x500 magnification using the image processing technique. Findings: The electrolyte with 5 g/l H2O2 additive have been elaborated as an optimal composition for synthesis of a coating with an increased content of corundum (a-Al2O3) as compared to a coating synthesized in the same mode in the 3KOH+2Na2SiO3 electrolyte without H2O2. This synthesis mode allows obtaining a coating with a high corundum content at low energy consumption. Research limitations/implications: For further optimization of the synthesis modes, it is necessary to analyse the influence of the phase composition and porosity of the obtained oxide ceramic coatings on their microhardness, wear resistance, and corrosion resistance. Practical implications: Based on the developed modes of synthesis of the coatings, it will be possible to obtain wear and corrosion resistant oxide ceramic coatings with predetermined functional properties and to reduce energy consumption for their formation. Originality/value: Methods for accelerating the formation of coatings have been proposed and tested, in particular, by adding various amounts of hydrogen peroxide to the electrolyte. The content of oxides in the obtained coatings, in particular, their ratios at various concentrations of hydrogen peroxide in the electrolyte, were determined by X-ray phase analysis. The modes of synthesis of the coatings were developed which allow obtaining a continuous coating without cracks with simultaneous decreasing porosity from 4.32% to 3.55-3.53%.

18

Boosting-based model for solving Sm-Co alloy’s maximum energy product prediction task

86%

Trostianchyn A. M. , Izonin I. V. , Duriagina Z. A. , Tkachenko R. O. , Kulyk V. V. , Havrysh B. M.

Archives of Materials Science and Engineering

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2022

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tom Vol. 116, nr 2

71--80

EN

Purpose: This paper aims to decide the Sm-Co alloy’s maximum energy product prediction task based on the boosting strategy of the ensemble of machine learning methods. Design/methodology/approach: This paper examines an ensemble-based approach to solving Sm-Co alloy’s maximum energy product prediction task. Because classical machine learning methods sometimes do not supply acceptable precision when solving the regression problem, the authors investigated the boosting ML model, namely Gradient Boosting. Building a boosting model based on several weak submodels, each of which considers the errors of the prior ones, provides substantial growth in the accuracy of the problem-solving. The obtained result is confirmed using an actual data set collected by the authors. Findings: This work demonstrates the high efficiency of applying the ensemble strategy of machine learning to the applied problem of materials science. The experiments determined the highest accuracy of solving the forecast task for the maximum energy product of Sm-Co alloy formed on the boosting model of machine learning in comparison with classical methods of machine learning. Research limitations/implications: The boosting strategy of machine learning, in comparison with single algorithms of machine learning, requires much more computational and time resources to implement the learning process of the model. Practical implications: This work demonstrated the possibility of effectively solving Sm-Co alloy’s maximum energy product prediction task using machine learning. The studied boosting model of machine learning for solving the problem provides high accuracy of prediction, which reveals several advantages of their use in solving issues applied to computational material science. Furthermore, using the Orange modelling environment provides a simple and intuitive interface for using the researched methods. The proposed approach to the forecast significantly reduces the time and resource costs associated with studying expensive rare earth metals (REM)-based ferromagnetic materials. value: The authors have collected and formed a set of data on predicting the maximum energy product of the Sm-Co alloy. We used machine learning tools to solve the task. As a result, the most increased forecasting precision based on the boosting model is demonstrated compared to classical machine learning methods.

19

Fatigue crack growth resistance of welded joints simulating the weld-repaired railway wheels metal

72%

Ostash O. P. , Kulyk V. V. , Poznyakov V. D. , Haivorons’kyi O. A. , Markashova L. I. , Vira V. V. , Duriagina Z. A. , Tepla T. L.

Archives of Materials Science and Engineering

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2017

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tom Vol. 86, nr 2

49--55

EN

Purpose: The aim of the paper is to study the structure and fatigue crack growth resistance characteristics of weld metal (WM), and heat affected zone (HAZ) under cyclic loadings for the development of railway wheels weld-repairing technology. Design/methodology/approach: WM and HAZ of the welded joint were investigated. The welded joint of 65G steel (0.65 mass.% C; 0.19 Si; 0,91 Mn), which is a model material for high-strength railway wheels, was received by welding Sv-08HM wire per linear welding energy of 10 kJ/cm. Regimes of welding were selected so that the cooling rate of the metal in the temperature range 500-600°C was 5°C/s. As a result, the bainite structure in WM and bainite-martensite one in HAZ are formed. To eliminate the residual stresses generated after the weld cooling, heat treatment was proposed: holding at 100°C for 2 hour after cooling under temperature below then that at the beginning of martensite transformation. Fracture resistance under cyclic loading was estimated by fatigue crack growth rates diagrams (da/dN vs. ΔK) according to standard method for compact tension samples testing. The microstructure and fracture surface were investigated using an optical, and electronic scanning and transmission microscope. Findings: Microstructure parameters and fatigue crack growth resistance characteristics of WM and HAZ after the proposed heat treatment, and also residual stresses of the second kind and local strains in the bulk of bainite and martensite are obtained. Research limitations/implications: Investigations were conducted on samples that simulate the structure and properties of real renovated railway wheels made of steel with high content (0.65%) of carbon. Practical implications: Service durability and safety of weld-repaired railway wheels under high service loadings is increased. Originality/value: HAZ is the most dangerous zone in terms of fatigue cracks initiation and propagation in elements repaired by surfacing method. The positive result on the proposed heat treatment influence is received since the fatigue crack growth resistance characteristics of HAZ metal with bainite-martensite structure raise to the level of weld metal.

20

An effective crack tip region finite element sub-model for fracture mechanics analysis

72%

Lenkovskiy T. M. , Kulyk V. V. , Duriagina Z. A. , Kovalchuk R. A. , Topilnytskyy V. G. , Vira V. V. , Tepla T. L. , Bilash O. V. , Lishchynska K. I.

Archives of Materials Science and Engineering

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2017

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tom Vol. 87, nr 2

56--65

EN

Purpose: To create an effective in engineering strength calculation three-dimensional submodel of the near crack tip region in solids for hi-fidelity analysis of their stress-strain state by the finite element method. Design/methodology/approach: To create a volume near the crack tip, regular threedimensional 20-node prismatic isoparametric elements and 15-node special elements with edge length of 12.5 μm with shifted nodes in order to simulate the singularity of stress at the crack tip were used. Using these two types of elements, a cylindrical fragment of diameter of 100 μm was built. In its base is a 16-vertex polygon, and its axis is the crack front line. In the radial direction the size of the elements was smoothly enlarged by creating of 5 circular layers of elements, and in the axial direction 8 layers were created. For convenience of the sub-model usage, the cylindrical fragment was completed by regular elements to a cubic form with edge size 400 μm. For the sub-model approbation, the full-scale three-dimensional models of standard specimens with cracks were built. The stress intensity factor K at normal tension was calculated assuming small scale yielding conditions in a plane between 4th and 5th layers of special elements on the basis of analysis of displacement fields near the crack tip. Findings: An effective three-dimensional sub-model of the near crack tip region is proposed. The sub-model was used to obtain the dependence of the stress intensity factor on the relative crack length at normal tension for four types of standard specimens. The obtained dependences show excellent correlation with known analytical solutions. Research limitations/implications: The concept of finite element meshing at threedimensional modelling of the near crack tip region for high-fidelity stress-strain state analysis was generalized. A sub-model of the near crack tip region was created and used to determine the stress intensity factor at normal tension of four types of standard specimens. It is shown that the proposed methodology is effective for precise analysis of the stressstrain state of solids with cracks within the framework of linear fracture mechanics. Practical implications: By applying the generalized approach and the proposed threedimensional sub-model of the near crack tip region, one can determine the stress-strain state of structure elements and machine parts when analysing their workability by the finite element method. Originality/value: An effective finite-element sub-model for the stress-strain state analysis in the vicinity of the crack tip within the framework of the linear fracture mechanics is proposed.