Ukrainian Journal of Mechanical Engineering and Materials Science. – 2018. – Vol. 4, No. 1

Permanent URI for this collectionhttps://ena.lpnu.ua/handle/ntb/44113

Науковий журнал

Засновник і видавець Національний університет «Львівська політехніка». Виходить двічі на рік з 2015 року.

Ukrainian Journal of Mechanical Engineering and Materials Science = Український журнал із машинобудування і матеріалознавства : науковий журнал / Lviv Politechnic National University ; editor-in-chief Oleksiy Lanets. – Lviv, 2018. – Volume 4, number 1. – 174 p. : il.

Ukrainian Journal of Mechanical Engineering and Materials Science

Зміст (том 4, № 1)


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Content (Vol. 4, No 1)


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    Semi-active vibration absorbers for the high-rise objects
    (Lviv Politechnic Publishing House, 2018-01-29) Diveyev, Bohdan; Lviv Polytechnic National University
    To determine the optimal parameters of the dynamic vibration absorber (DVA), a complete multi-parameter model of the dynamics of machines and structures is required. A model with two degrees of freedom is unacceptable for a sufficiently precise calculation with sufficient accuracy of the oscillations of the design, and thus for an adequate description of its dynamic characteristics. Therefore, in practice, it is necessary to investigate the design using a complex model. In particular, the methods for determining the concentration of mass and stiffness can be used on the basis of a refined theoretical calculation. A number of numerical schemes (NS) are known for complex vibro-loaded structures, in which developed methods of decomposition and synthesis of NS based on new methods of modal synthesis. Also developed is a complex NS of discrete-continuum type, which provides an opportunity in the adaptive mode to calculate stresses not only in the continuum elements, but also in the places of their greatest concentration - in the compounds. In this paper, an efficient numerical approach based on the theoretical-experimental method is proposed to maximize the minimal damping of modes in a prescribed frequency range for general viscous tuned-mass systems. Methods of decomposition and numerical synthesis are considered on the basis of the adaptive schemes. The influence of dynamic vibration absorbers and basic design elastic and damping properties is under discussion. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in sinusoidal and impact forced tall buildings system. One task of this work is to analyze parameters identification of the dynamic vibration absorber and the basic structure. The discrete-continue models of machines dynamics of some elongated element with multi mass DVA’s are offered. A technique is developed to give the optimal DVA’s for the elimination of excessive vibration in harmonic stochastic and impact loaded systems. The questions of robustness at optimization of DVA are considered. Different types of control management for semi-active DVA’s are applied. Examples of DVA’s practical implementation are presented.
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    Resonant phenomena of elastic bodies that perform bending and torsion vibrations
    (Lviv Politechnic Publishing House, 2018-01-29) Andrukhiv, Andrij; Sokil, Bohdan; Sokil, Mariia; Lviv Polytechnic National University
    The method of study of the influence of torsional oscillations of one-dimensional models of nonlinear elastic bodies, along which moves with a constant velocity continuous flow of inelastic homogeneous medium, into bending, is developed. It is believed that information on torsional oscillations is known from empirical studies. Based on the latter, the refined model of the dynamics of the process of the investigated object is constructed. The latter is a boundary value problem for nonlinear nonautonomous differential equations with partial derivatives. The imposed restrictions on power factors and the main parameters of torsional oscillations allow for the analytical study of the dynamics of the process to use the basic ideas of the asymptotic integration of equations with partial derivatives. With their help, we obtain a two-parameter set of solutions that describe the determinant parameters of bending vibrations of an elastic body. It is established that for the considered elastic body there can be resonance oscillations, which are caused not only by external factors, but also by internal – torsional oscillations. Regarding the law of the change in the basic parameters of the dynamics of the bending motion of an elastic body, its rotation around the vertical axis reduces the frequency of its own flexural oscillations of the body, and even small torsional oscillations cause an additional periodic action on the transverse. In connection with the above bending vibrations of the elastic body, which performs complex oscillations (torsion and bending), resonances are possible both at the frequency of the external periodic perturbation and at the frequencies of the torsional oscillations (internal resonances). The amplitude of the transition through the resonance: a) at the basic frequency of external perturbation takes less value for elastic bodies of greater flexural rigidity and for higher values of the relative motion of the medium; b) at the frequency of torsional oscillations for larger values of the angular velocity takes more importance; c) with “fast” transition through resonance at the frequency of external or internal perturbation is less than with “slow”. The obtained results can serve as the basis for the choice of operating parameters of elastic elements of machines that carry out complex oscillations.
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    Structure and wear resistance of aluminium alloys coated with surface layer laser-modified by silicon carbide
    (Lviv Politechnic Publishing House, 2018-01-29) Student, Mykhaylo; Pokhmurska, Hanna; Zadorozhna, Khrystyna; Dzyubyk, Andrii; Khomych, Ivan; Karpenko Physico-Mechanical institute of the NAS of Ukraine; Lviv Polytechnic National University
    Modern approaches to ensuring the necessary characteristics of surface of a material with the aim to improve economic and technological characteristics of the structures are considered in this paper. It is shown that aluminium alloys gain wide application in industry. Nevertheless, surface characteristics of materials are insufficiently good for their use in structures which operate under abrasive wearing and boundary friction. The use of the method of surface modification by a concentrated light-beam of energy is of prospect. Analysis of literature data indicates that in the course of laser-modification of surface of an aluminium alloy it is possible to form a material whose operational characteristics are higher than those of the material in its initial state. However, herewith it is important to quantitively estimate properties of the obtained composite layer on the surface of the article as well as to estimate the distinction between the layer and the main metal. The microstructure of laser-modified composite layers of aluminium alloys which had been formed by means of direct blow-in of SiC powder into the melted by laser radiation zone of surface has been investigated. Laser reinforcement of surfaces of aluminium alloys by SiC particles causes pronounced inhomogeneity of structure of surface layers of alloys. It has been shown that preliminary heating of specimens in the course of their laser-treatment increases the depth of the modified layer over the whole zone of treatment and improves the uniformity of distribution of reinforcing SiC particles; however, because of turbulence in the melt there is observed some non-uniformity of distribution of SiC particles in the modified layer. It is found that in the interaction of Al melt with SiC particles there forms plates of Al4C3 carbide at the interface, these plates grow mainly co-axially to the orientations of SiC crystals in the direction to the melt. Besides, in the matrix there takes place partial dissolution of SiC with formation of needle-shaped Al4C3 carbides. During the modification of surfaces of these alloys, in the case of increased concentration of silicium in the melt there is also observed inclusion of pure silicium. Besides, there is also possible the diffusion of aluminium into thin near-surface layer of silicium carbide, the layer separates from SiC crystal (phenomenon of ply separation) when the concentration of aluminium reaches a value of 3–5 %. It is established that the abrasive wear resistance of the non-modified AD35 alloy, which is determined according to the method of rigid abrasive wheel, is by 30–45 % higher than that of B95 alloy. In this case, the deterioration (wear-and-tear) proceeds according to the following two mechanisms: (1) by cutting and (2) by adhesive grafting between the abrasive wheel and the aluminium alloy by tearing out alloy particles from the surface. Optimal regimes of laser reinforcement of surfaces of aluminium alloy by means of fine SiC particles have been determined in this paper; this enabled us to increase 40–70 times the wear resistance of aluminium alloys in comparison with non-modified alloys when they are subjected to friction by rigidly fixed abrasive particles. The same reinforcement almost two times increases the wear resistance in dry reversive friction, and it increases the wear resistance only by 10–25 % in wearing by loose abrasive particles.
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    Research of volt-ampere characteristics of the wire pierce electron gun at electron-beam microprocessing of dielectrics
    (Lviv Politechnic Publishing House, 2018-01-29) Bondarenko, Maksym; Antonyuk, Viktor; Kovalenko, Yurii; Rud, Maksym; Haidash, Roman; Cherkasy State Technological University; National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”
    The article considers the basic energy characteristics of a wire Pierce electron-beam gun, which used for microprocessing of dielectric materials in vacuo. The aim of the work is to determine the optimal regimes of electron-beam microprocessing of dielectric materials by studying the volt-ampere characteristics of the wire Pierce electron-beam gun. In the methodical part of the scientific work, a technological experiment with electron-beam microprocessing of dielectric surfaces is proposed, and also identified and studied the operating modes of the Pierce electron-beam gun in depending on their energy characteristics. As a result, the analysis of the obtained results of electron-beam microprocessing of surfaces of dielectric materials makes it possible to increase the reproducibility of the results of such treatment in terms of purity and residual nanorelief by 18–25 %. The comparison of the results of experimental electron-beam microprocessing of dielectrics with the results of their laser processing made it possible to establish a decrease in the residual microroughness of the surface of the optical glass K8 by 17...27 times with electron-beam microprocessing and by 12–14 times with surface laser treatment. Wherein, surface laser processing does not allow to eliminate the undulation of the surface, which is related to the specificity of the interaction of the laser beam with the surface of the optical material, whereas, when processing by the ribbon-shaped electronic stream such undulation does not appear. Conclusions and analyzed data obtained in the article based on the results of experimental studies can be used to optimize the technological regimes of electron-beam microprocessing in the production of micro-optics products, integrated optics, microelectrooptics, nanoelectronics, etc.
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    Application of wear-resistant coating by electrospark alloying method using an eutectic electrode material
    (Lviv Politechnic Publishing House, 2018-01-29) Bilous, Oleksiy; Mahura, Bohdan; Lviv Polytechnic National University
    Analysis of the literature database connected with the usage of an electro-spark alloying (ESA) for tool hardening has been carried out in the article. Necessity of developing a new tungstenless electrode materials with eutectic structure for improvement of an electro-spark alloying technologies has been proved. Therefore, the structure of a new eutectic Fe-Mn-C-B-Si-Cr-Li alloy system has been developed and manufacturing techniques of an alloying by a sintering method has been offered. The article presents the scientific data obtained on the modern equipment. Electronic spectroscopy – spectral analysis of an eutectic electrode alloy has been carried out by an electronic spectrometer of JAMP-10S model (JEOL). X-ray phase analysis of the alloy has been carried out on the “Dron-UM1”.
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    Kinetics of high-temperature interaction of titanium alloys with a carbon-containing gaseous medium
    (Lviv Politechnic Publishing House, 2018-01-29) Trush, Vasyl; Luk’yanenko, Alexander; Karpenko Physico-Mechanical institute of the NAS of Ukraine
    Due to their excellent complex of physical, chemical, and mechanical properties, titanium alloys are unique materials for many branches of industry. An important feature of titanium is its high reactivity concerning the interstitial chemical elements (oxygen, nitrogen, and carbon). The absorption of interstitial elements by titanium alloys causes change in physical and mechanical properties of alloys and articles which are made of them. It should be noted that the titanium alloys are classified, in particular, by the compositions of their structures. Investigations of titanium alloys of different structural compositions will enable us to take into account the influence of their features on the kinetics of their interaction with interstitial elements. Results of experimental investigations of the influence of a carbon-containing gaseous medium on the kinetics of interaction of titanium alloys of different structural classes (α-, pseudo-α, and (α+β)) are presented in this paper. It is established that the interaction at high temperatures (T = 750–850 °C) of titanium alloys with rarefied carbon-containing gaseous medium (Ar+16.7 % C3H8) under a pressure of P = 0.116 Pa leads to the increase in mass of the specimens according to a law which is close to linear dependence on time.
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    Method for calculating the operating life of a steam pipe with a creep-fatigue crack near a weld joint
    (Lviv Politechnic Publishing House, 2018-01-29) Dolinska, Iryna; Palash, Roman; Karpenko Physico-Mechanical Institute of the NAS of Ukraine; Lviv Polytechnic National University
    A method for determining the period of sub-critical growth of a semielliptical creep-fatigue crack in the internal surface of a pipe wall of the steam pipeline is proposed. The crack is located near the ring weld in the field of residual stresses in the heat-affected zone. The dependence of the residual resource of the pipe of a steam pipeline with the weld joint on the location of the centre of the crack relative to the axis of the weld is ascertained.
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    Heat generation and heat consumption in engine of rapid internal combustion
    (Lviv Politechnic Publishing House, 2018-01-29) Hashchuk, Petro; Nikipchuk, Serhij; Lviv State University of Life Safety; Lviv Polytechnic National University
    The research of heat generation and heat consumption in a conventional or ideal engine provides useful information about the regularities, character of the process and effectiveness of fuel combustion in any real engine that cannot be subject to experiments. This information is advantageous both in case of heat transformation effectiveness analysis and the development of means to improve already employed engine. The procedure (algorithm) of thermal processes modeling that take place in the internal combustion engines should be developed in a way that enables, according to measured pressure of working gases, to adequately reconstruct the course of heat generation, and vice versa, relying on a set course of heat generation, to veritably identify the change of gases pressure in the cylinder. Research aim – based on the principle of analogy and harmonious combination of induction and deduction to evaluate the possibility to represent in a formal way and theoretically generalize experimentally identified information about the regularities of heat generation and heat consumption processes development in Otto-cycle engines (engines of rapid internal combustion). As a rule in case of analytical identification of heat generation – heat consumption processes the index a of combustion capacity is defined in advance. The acquired information, however, demonstrates that there are more reasons to consider the value of the parameter m to be set in advance, rather than of the parameter a. The relation between values of heat emission maximal intensiveness z& * and the time of its achievement t * in an empirical sense is seemingly parabolic. Theoretically, as it has been found out, it can be evidently treated as “fuzzy” hyperbolic. The fact that the engine’s idle run does not conform to the “hyperbolic” tendency manifests its considerable imperfection and does not contend against the theoretically substantiated regularity. Given, for example, that z& *t* »1, it is possible to acknowledge that m »1.93. While given m » 2 , we will have to acknowledge that z&*t* »1.03 . Thus, if we assign in advance that a = -6.908 we considerably limit the flexibility and preciseness of the identification algorism.
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    Corrosion-mechanical resistance of arc-sprayed coatings made from cored powders
    (Lviv Politechnic Publishing House, 2018-01-29) Student, Mykhaylo; Veselivska, Galyna; Gvozdeckii, Volodymyr; Golovchuk, Myron; Dzyubyk, Liudmyla; Sirak, Yaryna; Karpenko Physico-Mechanical institute of the NAS of Ukraine
    Result of investigations of resistance against corrosion and mechanical resistance of obtained by means of arc-spray metallization (with the use of cored wires) coatings are presented. The cored wires (CWs) enable us to regulate the chemical composition and, consequently, properties of the deposited coating in a wide range. With this, the characteristic feature is its high structural heterogeneity, which is caused by rapidness of the processes of melting of components of the CW in the arc; this promotes incompleteness of dissolving of change materials in the melt of the metallic shell, and thus, there forms of heterogeneous as to its chemical components melt. The determination of the first-type residual stresses in coatings was conducted according to the developed for bimetal rings technique. The tensile strength (cohesion) of ASC was determined with the use of an experimental set-up which consisted of two pipes. Electrochemical investigations were conducted in an electrochemical cell in potentiodynamic regime with the use of hard-ware-software complex which was designed for automation of investigations with the help of CBЛ-1Б-М voltamperometric system. The rate of corrosion was determined by means of extrapolation of linear segments of polarization curves to the potential of corrosion or on the basis of segments which corresponded to passive state. In order to develop experimental sets of CWs, there additionally were investigated some materials with different charge components (chromium, ferro-chromium, boron carbide, ferrochromium- boron, ferro-silicium, ferro-manganise, self-fluxing alloy) (Table 1). High hardness is characteristic of coatings made from CWs. Such a high hardness is due to 3 % of boron in the coating. However, the cohesive strength of such coating is low and does not exceed 100 MPa. This is caused by high tensile residual first-type stresses, which can lead to emergence of crack during machining. In order to reduce the level of residual stresses, it is necessary to preliminarily heat machine parts to 150–2000 °C. Electrochemical parameters and the character of polarization curves, despite some changes in chemical composition of coatings, do not essentially differ. With this, the potential of corrosion shifts towards the segment of negative values, and the corrosion current of such coatings are within one decimal order of their values. Open porosity, that is an important factor, which influences the corrosion behaviour of the material and its matrix is a characteristic feature of all the coatings. The corrosive medium, because of the presence of porosity, penetrates through such pores down to the matrix and creates conditions for proceeding of under-coating corrosion. In this case, products of corrosion accumulate at the coating – matrix interface, and they cause the separation of the coating from the basis (phenomena of ply-separation). The presence of chromium, ferro-chromium, ferro-silicon, and ferro-manganese in the charge for CW 90Cr17BMnSi leads to minimal chemical heterogeneity of the coating, and consequently to high corrosion resistance of the coating. The presence of ferro-chromium-boron, chromium, and self-fluxing alloying composition in the charge for CW 20Cr16B3Ni2SiAl ensures high content of chromium in the coating, low coefficient of microheterogeneity, and high resistance against corrosion.
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    Choose of optimal regimes of traffic light control in operating zone of pedestrian crossing
    (Lviv Politechnic Publishing House, 2018-01-29) Royko, Yuriy; Hrytsun, Oleg; Bura, Romana; Lviv Polytechnic National University
    On the given stage of motorization level development and increase of traffic flow intensity, with increasing frequency apply to the implementation of intelligent automated systems of traffic control. The quality of their work depends foremost from study of the primary factors of road users, their behavior, including the factor of a person as movement operator, geometric parameters of communication routes, road conditions as movement environment. Such study is held by methods of field research, documentary research and mathematical modelling. Considering transport system, it is necessary to have in mind that we are concerned with the large array of stochastic indicators which, during its normal operation, comply with the normal law of distribution. If the process of traffic flows movement control, including their attachment to the roadway, parameters of which are clearly regulated by standards, is studied relatively in detail, then regularities in pedestrian flows are underexplored only due to the fact that their behavior quite frequently is regulated. However, enough amounts of mathematical methods of description the different stochastic systems have appeared, based on which it is possible to perform the simulation of road users’ behavior, in particular pedestrians. In this work it is undertaken experimental research on pedestrians’ behavior on signaled pedestrian crossings in Lviv city for different functional zones and in different time of day, and also it is investigated dynamic factors in traffic flow with the aim of determination the rational (by duration) regimes of traffic light control, during which the amount and duration of delays in traffic flows and the possibility of accidents commission is reduced, which are the consequence of road users behavior. The backgrounds of these negative phenomena are: fluctuation of traffic flow intensity, when pedestrian during longtime restrictive signals can start to move on restrictive signal of traffic light, what is unexpected for vehicle driver, especially in nighttime when blinding appears; observation only the demands of normative documents during designing the communication routes what is not always adequate for different functional areas of settlements; absence of distinct regulation of range of traffic light control parameters which would create its optimal regimes considering traffic and pedestrian flows behavior.