Ukrainian Journal of Mechanical Engineering and Materials Science. – 2017. – Vol. 3, No. 1
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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, 2017. – Volume 3, number 1. – 134 p. : il.
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Item Operational conditions of vehicles motion and formation of urban driving cycle in the city of Lviv(Lviv Politechnic Publishing House, 2017-01-01) Vasyuhnyk, Juriy; Lviv Polytechnic National University, Lviv, UkraineTo the greatest extent, the indicators of the motor vehicles being in the normative technical state are influenced by the operational conditions, which, in turn, are characterized by road, relief (terrain) and transport conditions. The transport conditions of large cities of Ukraine are characterized by the intensive increase of motor transport, especially individual (private) one, on the street-road network of the city caused a number of problems, such as increased waste of time needed for a trip, increased number of forced stops, increased number of emergencies and road-traffic accidents, the occurrence of traffic jams, chemical and noise pollution of the environment. As the special investigations indicated, the volume of traffic has increased by 1.5…1.8 times in comparison with the data of ten years ago [1]. All this caused the necessity to substantiate the rational use of the power of the motor vehicles engines and to control their ecological indexes in order to reduce the negative influence on the environment. While evaluating the toxicity of the motor vehicles engines, two fundamentally different methods of investigations are being used: testing on steady-state operating conditions with constant parameters of the engine and testing on transient operating conditions when the input parameters are being changed. For the transient conditions, the main conditions of the motor vehicles motion have been identified: motion in the conditions of the city and motion out of its borders. Each of the conditions is characterized by the differences in the percentage of toxic components in the exhaust (burnt) gases. While developing the technique of determination of ecological indexes and parameters of fuel economy (saving) for motor vehicles, a large number of factors, which varies depending on the operating conditions, are considered. This is expedient in the case when the operating conditions are very different considering the typical motion conditions in the region and the several aspects that affect the fuel consumption. One of the main reasons for this is the unsatisfactory state of planning, accounting and standardization of the efficiency of the motor vehicles use. In this approach, the operation indexes are estimated based on not always impartial reporting and statistical data, so the standards are not an impartial factor or a model for the motor vehicles operation. These circumstances substantiate the urgency of the subject of research. While carrying out these investigations, the preliminary analysis of the motion conditions of the motor vehicles in different operating conditions is conducted and the peculiarities of the existing driving cycles of different countries of the world are considered. In order to ensure the determination of the motion conditions of motor vehicles in the conditions of the city of Lviv, the technique of investigations carrying out was developed on the basis of available means. The results of changing the conditions of the motor vehicles motion in the conditions of the city of Lviv were obtained taking into account the motion speed of the motor vehicle, the rotation frequency of the engine crankshaft, the instantaneous fuel consumption and the amount of consumed air. According to the results of the experiments carried out, the main features of the operational conditions of motor vehicles motion in Lviv were determined, the driving cycle for testing the motor vehicle in the conditions of Lviv and the method of comparative analysis of existing and improved driving cycles were developed. The analysis of indexes of existing and developed driving cycles is carried out and the expediency of use of the developed driving cycle is substantiated.Item Substantiation of the process of vertical transportation of piece loads(Lviv Politechnic Publishing House, 2017-01-01) Nishchenko, Iryna; Borovets, Volodymyr; Lviv National Agrarian University, Dubliany, Ukraine; National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine; Lviv Polytechnic National University, Lviv, UkraineThe urgent problem of automatization of the process of products transportation with a help of vertical chutes under the influence of gravitational forces using elastic elements is considered. The interaction between the object being transported and the elastic elements is defined. Their mutual influence on the transportation speed is determined depending on the contact parameters. The analysis of the object transportation speed changing depending on friction and on the zone of their mutual contact is carried out.Item Optimization of structure of sorting vibratory separators(Lviv Politechnic Publishing House, 2017-01-01) Shenbor, Vladyslav; Korendiy, Vitaliy; Brusentsov, Volodymyr; Lviv Polytechnic National University, Lviv, UkraineThe problem of substantiation of operational efficiency of vibratory separators designed on the basis of vibratory hopper feeders with electromagnetic vibrations exciters and with conic working bowls is considered in the article. The complex of factors influencing the accuracy and productiveness of separation of coins and disk-shaped products on two or more fractions is overviewed. New models of structures for the effective solution of separation problems are proposed. The design of a highly-efficient and high-performance separator with independent oscillations disturbance is described. The results of experimental investigations of vibratory transportation in elliptical modes of vibrations and of the study of separation efficiency are presented. The recommendations that developers and researchers of such devices may use are given.Item Hydrocutting of frozen food products(Lviv Politechnic Publishing House, 2017-01-01) Pogrebnyak, Volodymyr; National Technical University of Oil and Gas, Ivano-Frankivsk, UkraineThe article aims to determine the peculiarities of macromolecule deformation behavior under conditions of a jet-shaping head that would allow to solve the issue related to the mechanism of increasing water-jet cutting power with polymer additions. The roles of longitudinal and transverse velocity gradients in the manifestation of distinctive features of polymer solution flows are analysed. In converging polyethyleneoxide solution flow macromolecules are forced by a hydrodynamic field to rather strong stretching that causes the dynamic structure formation in solutions. There have been studied experimentally velocity fields and their gradients as well as the degree of macromolecule unrolling under pattern conditions of a jet-shaping head in polyethyleneoxide solutions flow. In converging polymer solution flow macromolecules are forced by a hydrodynamic field to rather strong (~ 60 % and more) stretching that causes the field restructuring. The determined regularities of macromolecules behavior in the flow under conditions of a jet-shaping head and manifested in this case effects of elastic deformations have paramount importance in understanding the mechanism of “anomalously” high cutting power of water-polymer jet. The work for the first time makes it possible to explain the nature of increased water-jet cutting power with polymer additions when cutting food products. Understanding the nature of increased cutting power of water-polymer jet will make it possible to develop recommendations on choosing regimes for water-polymer jet processing of food products by cutting.Item Dynamic properties predictions for laminated plates by high order theories(Lviv Politechnic Publishing House, 2017-01-01) Diveyev, Bohdan; Lviv Polytechnic National University, Lviv, UkraineThe main aim of this study is to predict the elastic and damping properties of composite laminated plates. Some approximate methods for the stress state predictions for laminated plates are presented. For simple uniform bending and transverse loading conditions, this problem has an exact elasticity solution. This paper presents a new stress analysis method for the accurate determination of the detailed stress distributions in laminated plates subjected to cylindrical bending. The present method is adaptive and does not rely on strong assumptions about the model of the plate. The theoretical model described here incorporates deformations of each sheet of the lamina, which account for the effects of transverse shear deformation, transverse normal strain-stress and nonlinear variation of displacements with respect to the thickness coordinate. Dynamic and damping predictions of laminated plates for various geometrical, mechanical and fastening properties are defined. The comparison with the Timoshenko beam theory is systematically done for analytical and approximation variants. The values of damping are got at a bend in three- and five-layered plates. For the threelayered plates the equivalent beam of Timoshenko exactly approximates a “sandwich” (with a soft damping kernel) dynamic properties of sandwich in a wide frequency range. For a plate with soft external layers the equivalent beam needs to be found in every frequency range separately. A hard bounded layer multiplies damping in a plate with soft external layers, however only at higher frequency of vibrations. For the high-frequency vibrations of plates the anomalous areas of diminishing of damping (for sandwiches) and increase are got for plates with soft covers. At the moderate amount of approximations the exact divisions of tensions are got in the layers of plates, thus the stresses continuity and surface terms are approximated exactly enough. Unlike the widespread theories of plates with the terms set a priori on surfaces (as a rule levels to the zero tensions) the offered equations allow to satisfy and complicated boundary conditions, instead of only free fastened plates. It allowed to explore the row of important examples for plates fastened in a hard holder and to explore influence of not only plates but also construction of holder on damping.Item Study of surface microstrains by electron speckle-interferometrymethods(Lviv Politechnic Publishing House, 2017-01-01) Gokhman, Olexsandr; Kondrya, Marianna; South Ukrainian National Pedagogical University named after K. D. Ushynsky, Odesa, UkraineDespite the fact that speckle interferometry methods began to develop more than 30 years ago, they still remain a rather exotic laboratory tool that has not received wide practical application in tensometry measurements and flaw detection. There are two reasons. The first one is the problem to interpret the interferograms by the right way. The second one is the extremely low measurement speed, which makes it impossible to use these methods for study of fast processes. In this paper we propose the advanced algorithm for electronic speckle interferometry (ESPI) method, which uses the arctangent of the intensity ratio of the speckles of two quarter-phase shifted specklograms, from that the position of the surface points with a known time step is calculated. Summing the increments of displacements after each measurement, we obtain a picture of the distribution of the strains of the surface of the object under study in the 3-dimensional representation customary for the experimenter. This approach effectively solves the first mentioned problem. While considering the second problem, it is shown that the measurement speed can be raised to the speed of the camera used (up to 1000 measurements per second in the flesh) if at the calibration stage a pair of speckles on the spectrograph is determined, whose phase is shifted by a quarter, and then take the arctangent of their ratio Intensities. In this case, there is no need to displace the reference beam, and the calculation of the displacement of the surface is made entirely from one specklogram only. Despite the fact that in this case the resolving power of the method bit decreases, the measurement speed increases substantially and there is no effect of the dynamic characteristics of the elements of the reference arm of the speckle interferometer on the measurement result, which is especially important in high-speed photography. The suggested algorithm for ESPI provides the extension of the diapason of recorded microstrains to hundreds of microns as well as on-line observation in 3D mode. New perspectives of nanoscale technologies could be opened on this way.Item Justification of efficiency of epicyclical gear train in device for speed changes management(Lviv Politechnic Publishing House, 2017-01-01) Strilets, Oleh; Strilets, Volodymyr; Lviv Polytechnic National University, Lviv, Ukraine; National University of Water and Environmental Engineering, Rivne, UkraineThe article analyses the functioning of epicyclical gear train with closed circuit hydrosystem, where the driving element is the sun gear and driven one is the carrier or vice versa. Control element is the ring gear, which rotates or can be stopped by the closed circuit hydrosystem. We have conducted a theoretical research of efficiency in such epicyclical gear train. Using the means of computer modelling, we have obtained graphical dependences of the transmission efficiency from its parameters. The analytical and graphical dependences have been obtained allow visually verifying the change of efficiency value and evaluating it in terms of self-braking.Item The influence of chemical-thermal treatment on granulometric characteristics of titanium sponge powder(Lviv Politechnic Publishing House, 2017-01-01) Trostyanchyn, Andriy; Lemishka, Ihor; Skrebtsov, Andriy; Ovchinnikov, Oleksandr; Lviv Polytechnic National University, Lviv, Ukraine; Zaporizhzhia National Technical University, Zaporizhzhia, UkraineThe phase composition and structure of powders of titanium sponge exposed to processes of chemical and thermal processing is investigated. As a result of X-ray analysis, it is found that after hydrogenation titanium powder consists of TiH2±х phase, while with the increase in the degree of phase dehydrogenation the percentage of TiH2±х decreases, and under perfect the dehydrogenation the structure consists mainly of α-Ti. Particle size analysis revealed that the partially dehydrated powders have the least degree of polydispersity. It is established that by means of regulation of technological regimes of hydrogenationdehydrogenation the two-phase structure with different ratios of α-phase to TiH2±х can be synthesized. It is shown that the presence of titanium hydride contributes to stabilization of the structure of formed powders.Item Propagation of plane elastic-tough-plastic waves in the materialwith yield delay(Lviv Politechnic Publishing House, 2017-01-01) Andrusyk, Yaroslav; Lviv Polytechnic National University, Lviv, UkraineThe use of electromechanical model of ideal elastic-tough-plastic material with yield delay while investigating the propagation of plane one-dimensional waves is being considered. The materials being investigated possesses the property of toughness only in the plastic region and is elastic up to the plastic state. The solving of the problem is being carried out in the conditions of one-parameter loading when the permanent (steady) uniformly distributed stress is being suddenly applied to the boundary surface of non-deformed half-space. The value of applied stress exceeds the limit level of elastic state in the case of static deformation and remains unchanged for the whole region of disturbed half-space. In order to conduct the corresponding calculation the dependence between the components the tensor of normal stress and linear deformations along the load axis is being determined. The defining equations of elastic-tough-plastic medium behind the front of the wave of transition from elastic to plastic state are being derived and the simple relationship for determination of the time (duration) of yield delay is deduced. The basic solution of these equations is obtained for the stresses in elastic and plastic region of the half-space. The special representation of the basic pattern of changing of lateral (transverse) stresses and longitudinal deformations for the region of active loading of material is defined. The distribution of velocities of the half-space points in the plastic region is obtained. The difference between the characters of propagation of plane elastic-plastic wave and the wave processes in the material with yield delay is shown. It is noted that two different solutions are obtained despite of the simple type of loading. The first one detects the strange character of medium’s behaviour when the material of disturbed halfspace in the plastic region is in the state of “trembling”, which causes the pulsations of lateral (transverse) stresses and the impulses of deformations along the axis that is normal to the boundary surface of the half-space.Item Investigation of influence of the train motion speed on the process of the rolling stock derailment in the presence of railway track oblique(Lviv Politechnic Publishing House, 2017-01-01) Batig, Andriy; Lviv Research Institute of Forensic Science, Lviv, UkraineThe article is aimed to construct the plots of speed range change, at which the necessary and sufficient condition of wheel rolling onto the rail head is satisfied, on the basis of generally accepted methodologies of the wheelset off-loading calculation. First of all, for the specific example, it is necessary to define the value of the train motion speed, at which it takes place the largest wheel off-loading on the curved section of the track with the existing oblique, to determine the minimal height of the oblique, at which the change of the train speed will not lead to the satisfaction of the necessary condition of wheel rolling onto the rail head. One should also construct a generalized scheme of checking the conditions of the rolling stock derailment if there is a railway track oblique of the certain value. In order to determine the influence of the train motion speed on the satisfaction of conditions of the car wheel rolling onto the rail head, it is necessary to solve the system of differential equations that describes the motion of the over-spring part of the rolling stock on the oblique track section under the influence of the forces applied to it. As a result of research carried out, there was obtained the value of train motion speed, at which the largest off-loading of the car wheel on the curved track section with oblique takes place. There was defined the minimal oblique value, at which the change of the train motion speed will not lead to the satisfaction of the necessary condition of the wheel rolling onto the rail head. There were constructed the plots of changing the speed range, at which the necessary and sufficient condition of car wheel rolling onto the rail head is satisfied. In the article, there was constructed the generalized scheme of checking the conditions of the rolling stock derailment if there is a railway track oblique. There were determined the speed ranges, at which the rolling stock derailment may occur if there is a railway track oblique of the certain value. There was defined the value of the train motion speed, at which the largest off-loading of the car wheel on the track curved section with the skew takes place. The obtained dependencies may be used for defining the safe range of the train motion speeds on the track sections with oblique of the certain value. They may be also used while carrying out the forensic railway-transport examinations.Item Applied model of assessment of intensity of the stressed deformed state of pipelines by evaluation ofmagnetic anisotropy of coercive forces. Part 1(Lviv Politechnic Publishing House, 2017-01-01) Biloborodchenko, Volodymyr; Lviv Polytechnic National University, Lviv, UkraineThe problem of applied diagnostics, statistically rigorous by the proposed model analogue, running stressed-deformed state of the main (trunk) shell is studied by the method of magnetic coercimetria. The relationship between the parameters of the loop of magnetic hysteresis is stochastically related with structural and mechanical state of the material of the pipeline wall and with the rest of equal conditions allows to effectively detect the zone of concentration of local stresses on the stage of their forming and development (propagation) on the basis of quantitative comparative analysis of their value with calculated equivalent mechanical stresses in principal (main) planes for particular pipe material considering that the operational stresses shouldn’t be larger than 30–50 %of the yield limit. The hypothesis H0 about the possibility of description of the measurement data of the stressed mechanical state by the magnetic-static method of coercimetria is made taking into account the peculiarities of disturbances caused by the operation of electric chains of the measuring apparatus during its metrological calibration. This hypothesis confirms that the arcsine function is a law of distribution probability density of the measured values of the coefficient of magnetic anisotropy as a response of the mechanical state of the pipe shell, that the parameter Q equals 0.95 on the confidence level and substantiates the evaluation of frequency of the influencing equivalent stresses in the whole range of loads applied to the shell by the inside normalized variable pressure. On the basis of corresponding scaling and renormalization of investigative values of the coefficient of magnetic anisotropy, the technique of determination of the level of mechanical stresses in the object of diagnostics is developed and the statistically rigorous compatibility in the certain range of influence of internal pressure in the pipeline is demonstrated using the results of preliminary metrological calibration of coercimeters obtained for different pipe steels.Item Modelling of the articulated vehicle dynamics taking into account the elastically fastened freight(Lviv Politechnic Publishing House, 2017-01-01) Zhytenko, Oleksandr; Zalutskyi, Yurii; Lviv Polytechnic National University, Lviv, UkraineIn this article, some methodological statements of the formation of mathematical models in the problems of machine dynamics are elucidated. The presence of a cushioned freight in the form of the fastened vehicle complicates the system, so that the equations describing its oscillations are too complicated and unsuitable for practical usage. It is shown that with all the complexity of the research object, it is expedient to form the mathematical model at the level of the design diagram (model) with a relatively small number of degrees of freedom. The peculiarities of mathematical modelling of the motion processes of specialized articulated vehicles for transportation of cars, namely, formation of the design diagram (model), making the necessary assumptions, choosing the independent coordinates and writing down the second-order Lagrange equations describing the system oscillations, are presented. While modelling, the most typical case, namely, the motion over the unit prominence (road shock), the effect of which on the wheels of the articulated vehicle is of the impact type, is considered. The choosing of the initial perturbation in the form of a unit impact is caused by the possibility of obtaining an impact characteristic, which is defined as the reaction of the system on the δ-function. In addition, under the impact action, it is possible to carry out the direct visual analysis of non-interfered single-frequency oscillatory processes, which allows to quickly obtain the approximate express-evaluation of the amplitude values of the process, frequencies of oscillations, as well as the oscillations damping decrement of the two-section articulated vehicle, if it is necessary. The mathematical model of the articulated vehicle consisting of a tractor and a semi-trailer in the form of a linear system having 9 degrees of freedom is developed. It consists of three cushioned masses, namely, the frame of the truck tractor, the frame of the semi-trailer and three non-cushioned masses, which are axles with wheels as an assembly. Both sections of this system are connected by the saddle-coupling element that is not absolutely rigid. While moving, the frames of the truck tractor and of the semi-trailer performs oscillatory motion in the vertical plane and angular oscillations about an axis passing through the centre of masses. The axles with wheels in the assembly oscillate only in the vertical plane. The peculiarity of the model is that the elastic and damping properties of the suspension of vehicle fixed on the semi-trailer are taken into account. The solution of the mathematical model allows to obtain the impact characteristic, to calculate the amplitude-frequency characteristic and to obtain the required (unknown) values of the root-meansquare accelerations of the non-cushioned masses. The technology of systemic consideration of the problems of formation of mathematical models in the form of block diagrams (structure charts) which are equivalent in dynamic relation to the systems of automatic control is offered.