Andrij Andrukhiv1, Bohdan Sokil2, Mariia Sokil3
1 Scientific Library, Lviv Polytechnic National University, 1, Profesorska Street, Lviv, Ukraine,
E-mail: andriy.i.andrukhiv@lpnu.ua
2 Department of Engineering Mechanics, Hetman Petro Sahaidachny National Army Academy,
32, Heroes of Maidan Str., Lviv, Ukraine, E-mail: Bogdan.I.Sokil@lpnu.ua
3 Department of Transport Technologies, Lviv Polytechnic National University, 12, S. Bandera Str.,
Lviv, Ukraine, E-mail: Mariia.B.Sokil@lpnu.ua
RESONANT PHENOMENA OF ELASTIC BODIES THAT PERFORM BENDING AND TORSION VIBRATIONS
Received: May 05, 2018 / Revised: June 23, 2018 / Accepted: June 26, 2018
© Andrukhiv A., Sokil B., Sokil M., 2018
Abstract. 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.
Keywords: nonlinear-elastic body; asymptotic methods; amplitude; resonance; complex fluctuations.

Кількість посилань 17

Iryna Dolinska1, Roman Palash2
1 Department of Acoustic Methods of Technical Diagnostics, Karpenko Physico-Mechanical Institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: ira_dolinska@ukr.net
2 Department of Welding Manufacture, Diagnostics and Restoration of Metal Structures, Lviv Polytechnic National University, 12, S. Bandera Str., Lviv, Ukraine, E-mail: rpalash@yahoo.com
METHOD FOR CALCULATING THE OPERATING LIFE OF A STEAM PIPE WITH A CREEP-FATIGUE CRACK NEAR A WELD JOINT
Received: October 23, 2017 / Revised: February 15, 2018 / Accepted: June 26, 2018
© Dolinska I., Palash R., 2018
Abstract. 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.
Keywords: welded joint, steam pipeline, creep-fatigue crack, residual resource, period of sub-critical growth of the crack.

Кількість посилань 13

Mykhaylo Student 1, Galyna Veselivska 2, Volodymyr Gvozdeckii 3, Myron Golovchuk 4,
Liudmyla Dzyubyk 5, Yaryna Sirak 6
1 Department of Superficial Strengthening of Structural Materials, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: student-m-m@ipm.lviv.ua
2 Department of Superficial Strengthening of Structural Materials, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: okhota@ipm.lviv.ua
3 Department of Superficial Strengthening of Structural Materials, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: gvosdetcki@gmail.com
4 Department of Superficial Strengthening of Structural Materials, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: pminasu@ipm.lviv.ua
5 Department of Engineering Mechanics and Dynamics of Machines, Lviv Polytechnic National University,
12, S. Bandera Str., Lviv, Ukraine, E-mail: Liudmyla.V.Dziubyk@lpnu.ua
6 Department of Superficial Strengthening of Structural Materials, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine, E-mail: pminasu@ipm.lviv.ua
CORROSION-MECHANICAL RESISTANCE OF ARC-SPRAYED COATINGS MADE FROM CORED POWDERS
Received: November 14, 2017 / Revised: April 09, 2018 / Accepted: June 26, 2018
© Student M., Veselivska G., Gvozdeckii V., Golovchuk M., Dzyubyk L., Sirak Ya., 2018
Abstract. 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, ferro-chromium-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.
Keywords: arc-sprayed coatings, cored powders, corrosion, metallization, residual stresses, electrochemical parameters, porosity.

Кількість посилань 10

Mykola Vorobyov1, Denis Prokopenko2
1Department of Applied Mechanics, Ivano-Frankivsk National University of Oil and Gas,
15, Karpatska Str., Ivano-Frankivsk, Ukraine, E-mail: :teormech@nung.edu.ua
2Department of Applied Mechanics, Ivano-Frankivsk National University of Oil and Gas,
15, Karpatska Str., Ivano-Frankivsk, Ukraine, E-mail: Deniss_2005@ukr.net
HYDRAULIC PUMP BASED ON THE ROLAMITE MECHANISM
Received: February 15, 2018 / Revised: May 07, 2018 / Accepted: June 26, 2018
© Vorobyov M., Prokopenko D., 2018
Abstract. When designing pumping equipment the question arises not only of the improvement of the existing types but also the search for a new principle of uniting the supporting elements with the elements of the formation of the working cameras of the pump. The purpose of the work is to provide a substantiation of the possibilities and expediency of designing a de-axial pump based on the Rolomite mechanism. Conditions ensuring the efficiency of the mechanism are considered on the basis of a specific hydraulic pump; the principle of inlet and outlet windows placement is justified. Analytical calculation of camera areas with the help of the created model in SolidWorks is provided and the coefficient of liquid compression is determined. The graphs of changing the areas of large and small cameras are presented.
The use of an electromagnet as a drive makes it possible to transfer the rotation into a closed space, which makes it possible to abandon bearings, seals, and also significantly simplifies the technological process of pump elements manufacturing. The flexible tape allows reducing the slip friction and getting a separate camera, which makes it possible to pump two substances at a time. There is also a process of liquid magnetization in the pump, which reduces the corrosion of metal elements of the pump and the pipelines. Considering the benefits of these types of mechanisms, there is the prospect of their further research and implementation.
Keywords: hydro pump, Rolamite mechanism, rolling body, electromagnetic drive.

Кількість посилань 14

Petro Hashchuk1, Roman Pelo2
1 Department of Operation of Vehicle and Fire-rescue Techniques, Lviv State University of Life Safety,
35, Kleparivska Str., Lviv, Ukraine, E-mail: petroh@meta.ua
2 Department of Operation and Repair of Automotive Vehicles, Lviv Polytechnic National University,
32, S. Banderа Str., Lviv, Ukraine, E-mail: Roman.A.Pelio@lpnu.ua
OPTIMAL GEAR SHIFT ALGORITHM
IN THE CAR TRANSMISSION DURING ITS DECELERATION
Received: April 24, 2018 / Revised: June 23, 2018 / Accepted: June 26, 2018
© Hashchuk P., Pelo R., 2018
Abstract. On the way to improving the car one can not avoid the problem of optimal gear shift in stage transmissions. Typically, the gear (stage) shift laws are distinguished, which are optimal because of fuel efficiency, either in terms of dynamics (speed), or in terms of comfort / safety of the car, etc. And all these types of laws are considered to be special, irreducible to each other. Because of this, in the designs of real automotive transmissions, it is often foreseen for the driver to have several automatic control programs at the same time. But everything that is entrusted to the driver is to some extent the subjective negation of automaticity and optimality.
The purpose of the work is to refute such very common system of views on the optimality of transmission control as: it turns out there is a single optimal gear shift law, within which there are no contradictions, at least between energy efficiency requirements and the requirements for the dynamics (or performance) of the vehicle.
The basis of the research methodology is the fully motivated principle of non-interference of the automatic transmission control system in the choice of the car movement program - a choice that is largely due to the circumstances and road conditions of the vehicle movement. So, optimizing the gear shift laws, it is necessary to consider the movement program to be predetermined (subject only to the driver), and the consequences of forced deviation from it during the operation of the elements of transmission control should be minimized. Specifically, gear shifting is considered during the car deceleration.
Direct involvement of the engine in the process of gear changes is envisaged, that is, the implementation of the principle of active synchronization of the rotation speed of separate parts of the transmission on adjacent gears during their shifting. In this case, the transmission of mechanical energy through the transmission is carried out by a continuous flow. The implementation of the dynamic principles of automation also leads to a decrease in the amount of mechanical energy that is transformed into heat during the skid of gear shift elements (frictions, for example). This makes it possible to increase the durability of the gear-shift elements or to impose lighter requirements in the process of designing the transmission.
The described algorithm of the optimal transmission control of the car provides grounds for the formation of motivated guidelines for selecting the moments of gear shift also during purely manual control of the car. The obtained results are quite general, although significant simplifications were introduced into the car model. In particular, the scheme of the gearbox, considered to be very simple, actually fully reproduces the principles of work of the mechanical stage transmission of any structure. The process of gear shifting is so fast that the linearized reproduction of the operating modes of the “engine-transmission” system is quite natural and such that it can not distort the idea of the optimal functioning of the engine-transmission system.
Keywords: car, deceleration, stage transmission, gear shift law, fuel consumption, dynamics of movement.

Кількість посилань 13

Vasyl Trush 1, Alexander Luk’yanenko 2
1 Department of High Temperature Strength of Structural Materials in Gas and Liquid Metal Media, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine,
E-mail: trushvasyl@gmail.com
2 Department of High Temperature Strength of Structural Materials in Gas and Liquid Metal Media, Karpenko Physico-Mechanical institute of the NAS of Ukraine, 5, Naukova Str., Lviv, Ukraine,
E-mail: lukyanenko@ukrpost.ua
KINETICS OF HIGH-TEMPERATURE INTERACTION OF TITANIUM ALLOYS WITH A CARBON-CONTAINING GASEOUS MEDIUM
Received: April 18, 2018 / Revised: June 20, 2018 / Accepted: June 26, 2018
© Trush V., Luk’yanenko A., 2018
Abstract. 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.
Keywords: titanium alloy, reactivity, absorption, structural composition, kinetics, interstitial element, gaseous medium, specimen.

Кількість посилань 24

Yan Cheylyakh
Department of Metallurgy and Technology of Welding Production, SHEI “Pryazovskyi State Technical University”, 7, Universitetska Str., Mariupol, Ukraine, E-mail: yan.cheylyakh@gmail.com
REGULATION OF THE PHASE-STRUCTURAL COMPOSITION
AND METASTABILITY OF AUSTENITE BY ALLOYING ELEMENTS
AND PARAMETERS OF TEMPERING FOR INCREASE
WEAR-RESISTANCE OF Fe-Cr-Mn DEPOSITED STEEL
Received: January 29, 2018 / Revised: April 04, 2018 / Accepted: June 26, 2018
© Cheylyakh Y., 2018
Abstract. It is shown that under the influence of alloying (Cr, Mn, C, Si, Ti, N, V) during electric arc hardfacing with a flux cored wire, as well as technological tempering parameters at temperatures of 300–700 °C, the phase-structural composition of the cost-saving alloyed deposited steel (from 0 to 75 % quenching martensite and austenite), the degree of metastability of austenite are regulated. At optimal parameters of alloying and tempering, an increased wear resistance is achieved due to the development of the deformation induced martensite γ→α' transformation of austenite during the wear process, which causes the effect of self-strengthening during testing and operation. This is an important advantage of the developed metastable deposited steel before the deformation-stable metal.
Keywords: deposited steel, alloying, metastable austenite, martensite, tempering, wear resistance.

Кількість посилань 17