Ukrainian Journal of Mechanical Engineering and Materials Science. – 2019. – Vol. 5, No. 1

Permanent URI for this collectionhttps://ena.lpnu.ua/handle/ntb/49612

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 : Lviv Politechnic Publishing House, 2019. – Volume 5, number 1. – 104 p.

Український журнал із машинобудування і матеріалознавства

Зміст (том 5, № 1)


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Start date: 2019End date: 2019

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    Elements of the theory of closed-loop mechanisms formed by rolling bodies without kinematic sliding
    (Видавництво Львівської політехніки, 2019-03-20) Vorobyov, Mykola; Prokopenko, Denis; Ivano-Frankivsk National University of Oil and Gas
    In the modern industry, it is impossible to do without high-tech equipment, for the designing of which the practical experience and experience of scientists are used. The main principles of engineering mechanics are based on the improvement of technical processes that promote creating certain conditions for the development of the manufacturing industry. An innovative approach to solving the problems of designing and creating any equipment makes it possible to combine new technologies and scientific and technical studies. When designing process equipment, there is a need not only to improve the existing types but also to search for new principles for connecting the supporting elements. It is important to create the right conditions for the effective functioning of reliable mechanisms. The main elements of the process equipment are the supporting ones. Among them, the bearings are the most important elements. Their reliable and long-term operation depends on the structural features of the supports. When designing the bearing units, they take into account the purpose of the mechanism, its operating conditions, the magnitude and direction of the loadings applied to the bearings, the required resource, the rotation frequency, the temperature and the state of the environment. In real bearings, there are no two fixed guides, and the separation is ensured by an intermediate element, which is connected by sliding friction. Besides, modern oil and gas equipment also usesradial supports through which a working fluid circulates with impurities of abrasive particles, which quickly destroys this element. Therefore, there is a need to create a scientific basis for the design of fundamentally new modern bearings. The purpose of the work is to find the optimum range of existence of closed-loop mechanisms formed by rolling bodies without kinematic sliding and to obtain the analytical dependences that relate the geometric parameters of the bearings to the separation by the rolling bodies in the absence of sliding. In this case, all three drive types are considered: from the outer or inner clip or the two clips together. To ensure the workability of all types of radial bearings, a range of specific basic conditions should be met. Given the significant advantages of these types of mechanisms, the challenge arises for their further study, with a view to wide implementation and practical application. The results can be useful for designing support elements for equipment used in many manufacturing fields.
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    Influence of the ignition system parameters on the ecological indicators of the automobile gas-fueled engine
    (Видавництво Львівської політехніки, 2019-03-20) Brytkovskyi, Vasyl; Kachmar, Roman; Lanets, Olena; Lviv Polytechnic National University
    The structure of the automobile service, since the beginning of the independence of Ukraine, has changed acutely. The number of private vehicles, the quality of service of which depends on the owner only, has increased. In addition to already existing automobile transport enterprises which has at least some existing production facilities with available cars of post-Soviet production and Russian cars of the middle time of Ukraine's independence, a large number of private small motor vehicles companies without any production base have appeared (in the best occasion with the available storage area), technical condition of the movable composition of which does not meet the requirements of European countries and the main transporting direction of these enterprises was concentrated in the directions of post-Soviet countries. In order to maximize efficiency, the owners of such vehicles carry out the transformation of power supplies to the system supplied with gas fuel. Despite the sufficient number of advantages, such refurbishment requires the introduction of constructive modifications and adjustments also in the ignition system of motor vehicles. And here, in the absence of systematic state control, many of the car owners in pursuit of maximum economy, trying not to make changes, causing violations in the work of car systems, which leads not only to the growth of fuel consumption and reducing of the effective performance of the engine, but also to increasing of emission of toxic components with the exhaust gas flow of the car engines. In conditions of Ukrainian cities, where emissions of toxic components by transport sources are up to 90% of all harmful effects [11], the search for ways to improve the system of technical service of vehicles is relevant in order to control and reduce the level of environmental hazards from the operation of vehicles. Therefore, researches that focus on determining the influence of regulation of the ignition system of engines powered by gas fuel, on the example of the spark plug gap influence on the indicators of the content of the components of the exhaust gases, are relevant. The method of research on the influence of the spark plug gap on the change in the composition of exhaust gases was developed in the paper, the research was carried out on ZAZ Lanos 1.4 engine MeMZ 317, on which is an assembly of gas equipment of the 4th generation Stag 200 GoFast. All experiments were carried out on the equipment of the Training Center for Computer Diagnostics of Vehicles “Lviv Polytechnic – Bosch Academy”. A set of new Champion RN9YC spark plugs was used, the gap of which was changed from 0.6 to 1.4 mm with a pitch of 0.1 mm. According to the values of the gap between the electrodes of the spark plug, with the use of Bosch BEA 460 gas analyzer, the content of the following components of the exhaust gases CO, HC, O2 and CO2 is determined for two engine's crankshaft frequencies.
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    Substantiation of structure and parameters of pneumatic system of mobile robot with orthogonal walking drive
    (Видавництво Львівської політехніки, 2019-03-20) Korendiy, Vitaliy; Zinko, Roman; Muzychka, Diana; Lviv Polytechnic National University; Dniprovsky State Technical University
    Problem statement. Mobile robots have awoken a large interest between scientists and designers in the last few years. One of the prospective drives of such robots is based on pneumatically operated system with no use of electric, heat, magnetic or other types of energy. Purpose. The main purpose of this research consists in substantiation of structure and parameters of pneumatic system of mobile robot with orthogonal walking drive. Methodology. The research is carried out using the basic laws and principles of mechanics, pneumatics and automation. The numerical experiment is conducted in MathCAD software and computer simulation of the robot’s motion is performed using SolidWorks software. Findings (results) and originality (novelty). The improved structure of the mobile robot with orthogonal walking drive is proposed. The pneumatically operated system ensuring the robot’s motion is substantiated. Practical value. The proposed design of walking robot can be used while designing industrial (production) prototypes of mobile robotic systems for performing various activities in the environments that are not suitable for using electric power. Scopes of further investigations. While carrying out further investigations, it is necessary to ensure the possibility of changing motion direction of mobile robot by means of pneumatic drive. In addition, it is expedient to design the devices for changing motion speed of the robot and the height of lifting of its feet.
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    Prediction of tribological properties of structural steels using artificial neural networks
    (Видавництво Львівської політехніки, 2019-03-20) Uvarov, Viktor; Bespalov, Serhii; G. V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine; Presidium of NAS of Ukraine; Technical Center of NAS of Ukraine
    The effect of quenching temperature on wear resistance of 40Kh steel after tempering has been investigated. It was found that compared to standard heat treatment, quenching from 1050 °С and high temperature tempering increase its tribological characteristics. The character of fracture of the contacting surfaces was studied. It was shown that in the specimens quenched from 860 °С and tempered, the fracture of the contact surface occurs by the mechanisms of smooth splitting and delamination with plastic deformation. Increasing the quenching temperature to 1050 °С along with high temperature tempering changes the character of the contact surface destruction. The areas with a distinctive microstructure appear on the surface exhibiting substantially higher wear resistance during friction as compared to the surrounding volume. The structural-geometrical parameters characterizing the roughness and bearing capacity of the contact interaction surface were analyzed. It was found that increasing the quenching temperature to 1050 °С allows to reduce the surface roughness and increase the bearing capacity. Using the methods of optical and transmission electron microscopy, the peculiarities of forming the microstructure of the investigated steel were studied, depending on the temperature conditions of the thermal treatment. It was shown that raising the quenching temperature to 1050 °С increases the austenitic grain size, enhances non-uniformity of carbon distribution, which leads to the formation of large needle-shaped crystals of lath martensite with microtwin boundaries inside. This, in turn, promotesthe formation at high tempering of non-uniformly distributed aggregates of coarse carbides at these microtwin boundaries. The aggregates form areas of microstructure with increased resistance to plastic deformation processes. That is, the morphology of the carbide phase is one of the main factors that determine the tribological characteristics of steel, namely roughness, structural-geometrical parameters and bearing capacity of the surface. The expediency of using artificial neural networks for prediction of tribological properties of structural steels was shown. According to the results of modeling the structural-geometrical parameters of the surface and the roughness characteristics, the bearing capacity of the 40Kh steel surface during friction was predicted.
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    Experimental determination of critical strain energy density of ductile materials
    (Видавництво Львівської політехніки, 2019-03-20) Molkov, Yuriy; Ivanyts’kyi, Yaroslav; Lenkovs’kyi, Taras; Trostianchyn, Andriy; Kulyk, Volodymyr; Shyshkovskyy, Roman; Karpenko Physico-mechanical Institute of the NAS of Ukraine; Lviv Polytechnic National University
    The method of experimental determination of strain energy density of plastic materials is developed. The technique for complete true stress-strain curves plotting is formulated. The standard hydraulic testing machine is equipped with specially designed experimental setup for Bridgman specimens testing at strain controlled tension loading with digital camera and light source for using digital image correlation method – a non-contact technique for strain and displacement measurement. The digital image correlation method was used to determine the local strain at the onset of fracture in the neck of Bridgman specimen. The technique takes into account the change of crosssection area in the neck of specimen due to internal crack propagation when calculating the true stresses. The complete true stressstress-curve of 40Kh alloyed steel is plotted end criticalstrain energy density of steel is determined from it. It is shown that the critical strain energy density of material, determined from the curve obtained by developed technique is 1.8 times higher than determined from the classical true stress-strain curve and is close to the value of the specific heat of fusion of steel. The curves built using the proposed technique can be used for setting material properties in stress-strain state calculations by finite element method at large scale yielding conditions, for instance at pressure vessels critical pressure calculation. The critical strain energy density value can be considered as a material property at fatigue life-time calculation using energy approach.
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    Substantiation of the shape of a solid oxide fuel cell anode using the stress-strain and shape-dependent crack deceleration approaches
    (Видавництво Львівської політехніки, 2019-03-20) Kuzio, Igor; Vasyliv, Bogdan; Korendiy, Vitaliy; Borovets, Volodymyr; Podhurska, Viktoriya; Lviv Polytechnic National University; Karpenko Physico-mechanical Institute of the NAS of Ukraine
    Stress and strain distributions in the YSZ–NiO spheroidal shape anode-substrate for a solid oxide fuel cell (SOFC) under pressure of operating environment were calculated using the finite element analysis. The features were then compared with ones of the cylindrical shape anode. The radii ranges for the cylindrical and spheroidal (segments of a sphere) parts of the anode ensuring its improved deformation resistance and more uniform stress distribution were suggested. Based on the calculations, an anode of the cylindrical shape with top and bottom convex surfaces (a spheroidal shape anode), with the spheroid to cylinder radii ratio R / Rc in the range from 5 to 20 is suggested. Itsspecific volume V / Sc isin the range from 1 to 2.5 mm. The stressesin the most dangerous areas (i. e. along the axis and the closed-loop fixing) and maximum strain, caused by external gas pressure on the anode working surface, are decreased by 10–30 % and 20–40 % respectively as compared to an anode of the cylindrical shape of the same radius and volume features. This increases the lifetime of a solid oxide fuel cell. A three-dimensional curve of intersection of the surfaces of stress distribution in the anode along its axis and the closed-loop fixing was approximated which displays the values of balanced stresses depending on V / Vc and R / Rc parameters. Also, the advantage of the spheroid shaped SOFC anode-substrate over conventional flat one was substantiated using a shape-dependent crack deceleration approach.
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    Substantiation of geometric parameters of discharge hopper hole at gravitational outflow of finely dispersed bulky material
    (Видавництво Львівської політехніки, 2019-03-20) Sholovii, Yurii; Maherus, Nadiia; Lviv Polytechnic National University
    The variability of physical and mechanical properties of finely dispersed bulky materials during processing and storage, the manner and height of filling the tanks; the terms and conditions of storage have a decisive influence on the choice of parameters of the discharge hoppers of bunkers with gravitational outflow. Therefore, the purpose of the article wasto justify the geometric parameters of the discharge hopper to provide a gravitational outflow of finely dispersed bulky materials. The geometrical parameters of the discharge hoppers were determined through mathematical simulation of the flow outflow of materials under the influence of gravity forces and the analysis of the tense state of bulky materials in the zone of outflow. As a result of mathematical simulation, the maximum diameter of the outlet of the hopper hole is determined, that implements the effect of "self-locking" the flow of the product is realized. The influence of physical and mechanical characteristics of finely dispersed bulky materials and angles the conical discharge hopper hole on the size of the outlet during the gravitational outflow is established. The mathematical model of the gravitational outflow of materials with conical discharge hopper hole, which takes into account the complexity of the nature of physical and mechanical connections between particles of materials is developed in the article. The research results allow to design bunkers for storage of finely dispersed bulky materials, to predict their behaviour with gravitational outflow and to ensure reliable operation of bunkers during their unloading. Also, in the future, it is advisable to carry out mathematical simulation of the process of gravitational outflow of finely dispersed bulky materials from bunkers of various cross sections and with different forms of the discharge hoppers.
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    Mathematical modeling of the thermoelastic state in a circular disk with a crack due to the action of the heat source
    (Видавництво Львівської політехніки, 2019-03-20) Zelenyak, Volodymyr; Kolyasa, Liubov; Lviv Polytechnic National University
    Purpose. To determine the two-dimensional thermoelastic state in a circular plate, weakened by an edge or internal crack induced by a stationary heat sourse. This paper proposes using singular integral equation (SIE) to investigate thermostressed intensity in the vicinity of the crack tip, depending on the local heat source placement and identify typical mechanical effects. Numerical results for the stress intensity factors (SIFs) can be potentially used to identify (with the limit equilibrium equations) critical values of the intensity of the local heat source at which crack begin to grow and the local destruction of the body. Methodology. The methods of studying two-dimensional thermoelastic state body with crack as stress concentrators based on the function of complex variable method by which the problem of stationary thermoelasticity are reduced to a SIE of the first kind, a numerical solution which was obtained by the method of mechanical quadratures. Findings. In this paper graphic dependences of stress intensity factors at the crack tip on the relative position of crack and local heat source placement and on the length of crack are obtained. Originality. Scientific novelty lies in the fact that the solutions of the new two-dimensional problems of thermoelasticity for a circular plate containing a crack under the influence of local heating of heat source. Practical value. The practical value is the ability to more fully take into account the real situation in the thermoelastic elements of engineering structures with cracks that operate under conditions of heat stress in various industries, particularly in mechanical engineering. The results of specific values in the crack tip SIF in graphs may be useful in the development of sustainable modes of structural elements in terms of preventing the growth of cracks.
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    Oscillation processes in a transmission with a dual-mass flywheel while moving a car from rest
    (Видавництво Львівської політехніки, 2019-03-20) Kindratskyy, Bohdan; Litvin, Roman; Lviv Polytechnic National University
    Problem statement. A wide range of modern engines, gearboxes, and massdimension characteristics of a car requires the development of efficient algorithms and methods of designing dual mass flywheels (DMFs) for the given transmission parameters. Improper selection of the design parameters of the DMF can lead to a deterioration of its properties and, consequently, to the increase of vibrations, reduction of the lifetime of the gearboxes, etc. Equally important is the problem of the DMF durability, which depends on many factors, in particular, the character of driving the car by the driver. The solution of the two mutually contradictory tasks formulated above is closely linked to the creation of simulation models of the car drive with a DMF, which will allow simulating different modes of the transmission operation, in order to optimize the parameters of the DMF to the specific design parameters of the car drive. The purpose. Taking into account the design features of the transmission and DMF, to develop and substantiate dynamic, mathematical, and stimulating models of the car drive with a DMF and to study the oscillation processes while moving a car from rest. Research methods. To construct a mathematical model of a car drive with a DMF, the Lagrange method of the 2nd kind was applied. To solve the differential equations of the car motion during acceleration and simulate oscillation processes in the transmission and DMF sections, we used numerical methods with their implementation in the MatLab Simulink environment. Results. A simulation model of a front-wheel car drive with a dual-mass flywheel has been developed in the Simulink environment. The oscillation processes in the transmission and elastic elements of the DMF by the case of moving the car of category M1 from rest were investigated. Recommendations were made to increase the lifetime of the DMF. The novelty. It has been found that the use of a DMF contributes to reducing the dynamic load applied to the drive sections, absorbing the vibration energy generated by the engine. The amplitude of torque oscillations in the transmission sections, semi-axles, and tires is approximately 1.4 times smaller in the DMF drive than in the single-mass flywheel drive. Increasing the energy dissipation coefficient in the DMF from 4 to 20 N·s·m leads to a decrease in the torque amplitude in the drive sections by 1.3–1.6 times at the beginning of moving the car from rest, reducing the duration of transient processes from 2 to 0.75 s, which eliminates the overloading of DMF elastic sections, increasing their lifetime. The practical value. A simulation model of a car drive with a DMF during the period of moving the car from rest has been developed, which makes it possible to simulate the influence of the design parameters of the drive and DMF on the loading of the elastic sections and to calculate their strength under long-term cyclic loading. Areas for further research. To investigate oscillation processes in the DMF and transmission sections under different modes of the car movement in order to determine ways to increase the DMF lifetime by reducing the influence of cyclic loading on their elastic sections.
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    Rheological properties of melts and X-ray method of study of cross-linked polyethylene
    (Видавництво Львівської політехніки, 2019-03-20) Shixaliyev, Karam; Abbasov, Ibrahim; Sadig, Khaver; Azerbaijan State Oil and Industry University
    In the paper, the X-ray study of cross-linked polyethylene with isopropenyl styrene or acrylonitrile was carried out. It is shown that cross-linking leads to a significant decrease in the area of the exothermic peak, an increase in the resistance of the structured system to thermal oxidation. These data confirm that the increase in resistance to thermal aging of polyethylene cross-linked with acrylonitrile or isopropenyl styrene fraction.