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
(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.
(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 , 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.
(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.
(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.
(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.