Ukrainian Journal of Mechanical Engineering and Materials Science. – 2020. – Vol. 6, 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 : Lviv Politechnic Publishing House, 2020. – Volume 6, number 1. – 92 p.


Recent Submissions

Now showing 1 - 10 of 10
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    Wear resistance of strengthened layers with nanocrystalline structure in friction with boundary lubrication
    (Lviv Politechnic Publishing House, 2020) Gurey , Volodymyr; Lviv Polytechnic National University
    Friction treatment refers to surface strengthening (hardening) methods using highly concentrated energy sources. The source of thermal energy occurs in the contact area of the tool-part due to high-speed friction (60–90 m/s) of the tool on the treated surface. The heating rate of the metal surface layer is 105–106 K/s. After moving the energy source from the contact zone, high speed cooling of the surface layer of the metal takes place. The cooling rate is 104–5∙105 K/s. Under the action of high-speed heating and cooling of the contact area of the tool-part in the surface layers, a strengthened (hardened) nanocrystalline (white) layer is formed. The formed nanocrystalline surface layer has other physical, mechanical, chemical properties in comparison with the base metal of the part. Studies have shown that in the process of friction treatment of working surfaces of parts made of Steel 40NiCr6 (quench hardening and low-temperature tempering) a strengthened layer with a thickness of 250–320 μm with a hardness of 7.6–9.2 GPa is formed. The grain size of the surface strengthened layer was 20–40 nm near the treated surface. The formation of the strengthened layer is influenced by the shape of the working surface of the tool. Thus, a strengthened layer of greater thickness and hardness is obtained when machining with a tool with transverse grooves on the working part than with a tool with a smooth working part. Experimental studies in friction with maximum lubrication of pair “Steel 40NiCr6 and Grey Cast Iron GG20” showed that the strengthened nanocrystalline layer significantly increases the performance during sliding friction. Only samples made of steel were strengthened, counter-samples made of gray cast iron were not strengthened. The wear intensity of strengthened pair is 2.2–3.1 times less compare to unstrengthened pair. During the friction of the strengthened pair, the coefficient of friction and the temperature in the sliding zone also decrease. The best results were obtained when studying the friction pair in which the samples were strengthened with a tool with transverse grooves on its working part.
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    Failure analysis of a motor vehicle suspension helical spring
    (Lviv Politechnic Publishing House, 2020) Bohun, Lidia; Pleshakov, Eduard; Shvachko , Sergiy; Lviv Polytechnic National University
    The purpose of this work is to reveal the cause of the failure of the motor vehicle rear suspension barrel-shaped spring with the progressive elasticity characteristic and predict measures to increase the lifetime of springs of this type. The fracture of the spring occurred on the middle coil, which operates under conditions of more severe stress in comparison with other coils. The chemical composition of the spring material, determined by X-ray fluorescence spectral and microstructural analyzes, corresponded to chromium-silicon steel 54SiCr6. In terms of structure and mechanical properties, the spring material met the standards. No traces of decarburization were detected, and no crack initiation, caused by non-metallic inclusions, was found in the material of the fractured spring. Macroscopic examination of the spring surface did not reveal any cracks, scratches, dents, traces of blows with stones and marks of spring coiling tool. Instead, extensive areas of exfoliation of the protective coating were found. The metallographic analysis revealed selective corrosion in the form of pitting damage in places of exfoliation of the protective coating. The fatigue crack propagates from the certain deep pit with the reorientation of the crack plane along the spiral surface to the central axis of the coil wire. After depletion of the safety margin, the spring broke down quickly. The fast fracture zone contains steps of the river pattern formed due to the spiral reorientation of the fracture surface. The research can be used to understand the importance of adhesive strength and wear resistance of protective coatings on the spring surface. Their local exfoliation causes subsequent corrosion damage to the spring, which stimulates its fatigue fracture.
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    Design and operational peculiarities of four-degree-of-freedom double-legged robot with pneumatic drive and turning mechanism
    (Lviv Politechnic Publishing House, 2020) Korendiy, Vitaliy; Zinko, Roman; Lozynskyy, Vasyl; Havrylchenko, Oleksandr; Lviv Polytechnic National University
    Problem statement. Mobile robots are of significant interest among scientists and designers during the last several decades. One of the prospective drives of such robots is based on pneumatically operated walking (stepping) system with no use of electric, heat, magnetic or other types of energy. This allows the use of pneumatically-driven robots in the cases when the use of other energy sources is prohibited (e.g., in some gaseous or fluid mediums). At the same time, the walking (stepping) type of moving increases the manoeuvrability and cross-country capability of the mobile robot, and decreases the harmful effect of its interaction with the supporting surface (e.g., the fertile soil surface) in comparison with wheeled or caterpillar drives. Purpose. The main purpose of this research consists in substantiation of structure and parameters of pneumatic system of four-degree-of freedom mobile robot with orthogonal walking drive and turning mechanism. 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; the computer simulation of the robot’s motion is performed using SolidWorks software; the modelling of the pneumatic system operation is carried out in Festo FluidSim Pneumatic software. Findings (results) and originality (novelty). The improved structure of the mobile robot with orthogonal walking drive and turning mechanism is proposed. The pneumatically operated system ensuring the robot’s curvilinear 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 іnvironments that are not suitable for using electric power or other types of energy sources. Scopes of further investigations. While carrying out further investigations, it is necessary to design the devices for changing motion speed of the robot and the height of lifting of its feet.
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    Study of the influence of the addition of an exothermic mixture and the ratio of the components of the exothermic mixture on the melting indices at FCAW
    (Lviv Politechnic Publishing House, 2020) Trembach, Bohdan; Grin, Aleksandr; Trembach, Illia; Donbas State Engineering Academy; Private Joint Stock Company “Novokramatorsky Mashinostroitelny Zavod”
    An important issue in the processes of strengthening and restoration of surfaces exposed to abrasive, abrasive-corrosive and hydroabrasive wear, using the process of self-protective flux-cored arc welding (FCAW), is to increase the productivity of hardfacing and the quality of the hardfacing metal. The literature review showed that one of the ways to increase the productivity of hardfacing and improve the quality of the hardfaced metal is to add an exothermic mixture to the core filler of flux-cored wire electrode. The effect of composition of filler core during FCAW on the fusion parameters, namely the addition of exothermic mixture (TM), the ratio of exothermic mixture components (CuO/Al), and the ratio of exothermic mixture oxidant to carbon content in the core composition (CuO/C) has been studied. It has been found that the optimum areas for the deposition rate (Gd), deposition factor (ad) and spattering factor (ψs) are observed for the following values of the core components: TM = 25…39, CuO/C = 5…6, CuO/Al = 3…4.
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    Comprehensive approach to training specialists in the area of engineering education
    (Lviv Politechnic Publishing House, 2020) Dzyubyk, Andrij; Nazar, Ihor; Dzyubyk, Liudmyla; Mykhailinchyk, Ihor; Kulykovets, Yurii; Lviv Polytechnic National University
    The article outlines advantages of applying a comprehensive approach to training specialists in the area of engineering education. Modern approaches to project management in production are analyzed, using the known experience of the European countries and the world. The basic tools of project management that are applied at all stages of implementation of engineering projects are described. Based on the analysis of known project management techniques, it has been established that effective engineering project management is possible by way of involving future professionals in the stages from developing the project idea, goals and objectives to obtaining the desired results and achieving the set goals. It is important to motivate students to think critically and encourage teamwork on a project. In the present article, the authors suggest to consider the process of training specialists in civil and industrial engineering through the prism of the next four phases of the project. The first phase is to prepare the project with elements of structuring. It addresses the issues of the project goals, tasks and results, risk management, project documentation, budgeting, formation and management of the project team. The second phase is project management, which includes drafting a project structural plan (PSP) and work packages, scheduling task completion, resources and costs planning, cost estimation, and time management tools. The third phase is the implementation of the project with control and monitoring. Here, future specialists are working on issues of the project control, financial monitoring, monitoring of resources, communication and interaction between teams, conflict management, change management and keeping necessary documentation. Completion of the project is the fourth stage, which is an integral element of project management. It provides for financial and analytical reporting, documentation for retention of experience, knowledge management, certification and feedback to the project team. Based on teaching practice and considerable practical experience in industry, the authors found out that the process of pedagogical training of future competitive specialists in various areas of civil and industrial engineering should be accompanied by practical and theoretical materials on modern tools for a holistic and integrated approach to project management. At the same time, taking account of the dynamics of political and economic changes in Ukraine and integration with international standards, it is necessary to take a skilled approach to the issue of production change management in the project activity. The global experience reveals that only truly successful organizations anticipate and initiate changes. Thus, the organizations themselves, their goals, objectives and tools are undergoing changes. And the issue of change management itself is the subject for further research by the authors.
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    Modeling of partially regular microreliefs formed on the end faces of rotation bodies bya vibration method
    (Lviv Politechnic Publishing House, 2020) Dzyura , Volodymyr; Ternopil Ivan Puluj National Technical University
    The scheme of formation of a set of variants of grooves of partially regular microreliefs formed on the end faces of rotation bodies by a vibration method has been developed, and the conditions of their existence have been determined. Using a block approach, mathematical models of partially regular microreliefs have been constructed, which described a set of their variants, taking into account such characteristics as the shape of axial lines of continuous regular microroughness, type, and location of axial symmetry lines of grooves, and groove shape. Using MathCAD software and developed mathematical models, graphic images of partially regular microreliefs were obtained.
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    The influence of measurement error on the risks of the consumer and the manufacturer when completing connections
    (Lviv Politechnic Publishing House, 2020) Kupriyanov, Oleksandr; Ukrainian Engineering Pedagogics Academy
    The influence of the measuring device error on the consumer’s and manufacturer’s risks was studied for three cases of the organization of completing: complete interchangeability, selective completing and completing with ranking. The presence of measurement error does not allow to avoid risks; however, their values must be estimated so that they do not have a significant impact on manufactured products. The study was carried out for a “shaft-hole” connection by statistical modeling, the laws of dimension distribution were accepted as normal, as well as the laws of distribution of measurement errors. For the case of completing with complete interchangeability, the accuracy of two-stage control was studied; it is recommended to establish the accuracy of the initial measurements at 20–25 % of the tolerance field, repeated measurements at 10–12 % of the tolerance field, while the manufacturer’s risk does not exceed 0.2 %, the consumer’s risk is practically zero. In the case of selective completing, the requirements for the accuracy of the measuring device are significantly higher than in the case of completing with complete interchangeability, since errors are possible not only at the limits of the tolerance field but also at the limits of the selection groups. Therefore, the measurement error should not exceed 5 % of the tolerance field width; it is also advisable to limit the number of selection groups. When completing with ranking, the accuracy of the measuring device has the least impact on risks, especially if the number of parts in the batch is large enough and the measurement error complies with the standards in mechanical engineering. It was established that for the number of sets greater than 10, almost complete assemblability is achieved and the risks associated with the measurement error become insignificant. Thus, if it is necessary to increase the accuracy of products at the assembly stage, it is recommended to use completing with ranking instead of selective completing.
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    Study of the processing of small diagnostic creations on a fluid sourcing by spiral survivals
    (Lviv Politechnic Publishing House, 2020) Karpyk, Karpyk; Kostiuk , Nazar; Ivano-Frankivsk National Technical University of Oil and Gas; Khmelnytsky National University
    The article considers the features of the drilling process where there is a change in temperature, hole diameter, and displacement relative to the axis and the impact on the tool, when machining holes with high-speed steel drills there is wear of the transverse edge which is completely rounded to create a conical surface. There is a decrease in the negative value of the front corners on the transverse edge of the decrease in axial force, which led to a decrease in the intensity of wear of the transverse edge. In order of increasing axial force, respectively, and the intensity of wear of the transverse edge, were sharpened and recommended sharpening methods that provide high performance of the drill, the greatest stability, increased drilling accuracy, as well as the lowest cutting force. The analysis of influence of technological methods and ways and equipment on accuracy and quality of deep openings of small diameter is carried out. The effects of the method of lubricating coolant supply on the tool stability and processing productivity are investigated. The analysis of processing on the metal-cutting equipment with constructive development of the device is executed. Also, the stress-strain state of the drilling process by the finite element method with the analysis of external influences on the twist drill is carried out. The results of the research substantiate and recommend technological methods that reduce the deformation of the tool and, as a consequence, increase the quality and accuracy of the dimensions of deep holes of small diameter.
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    Effect of mwcnt on surface roughness and burr height in mql milling of AISI 430 ferritic stainless steel
    (Lviv Politechnic Publishing House, 2020) Uysal, Alper; Dzhemilov, Eshreb; Dzhemalyadinov, Ruslan; Department of Mechanical Engineering, Yildiz Technical University, Turkey, Istanbul; Department of Mechanical Engineering, Crimean Engineering and Pedagogical University named after Fevzi Yakubov
    Stainless steel materials have been used in many fields such as automotive, aviation, medical industries, etc. In addition, these materials are classified as difficult-to-cut materials due to low thermal conductivity and work-hardening tendency. Therefore, studies on machining of these materials have been performed in order to understand the basic of the process. In this study, surface roughness and burr height were investigated in MQL (Minimum Quantity Lubrication) milling of AISI 430 ferritic stainless steel. In MQL milling, commercial vegetable cutting fluid and MWCNT (Multi Walled Carbon Nanotube) reinforced vegetable cutting fluid were used. The milling experiments were also conducted under dry condition. In the experiments, uncoated WC (Tungsten Carbide) and TiN (Titanium Nitride) coated WC cutting inserts were used. Based on the experimental results, MQL method reduced the surface roughness and burr heights and better surfaces were obtained by using nanofluids in MQL method.
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    Investigation of the effective parameters of scuffing failure in gears
    (Lviv Politechnic Publishing House, 2020) Bozca, Mehmet; Machine Design Division, Mechanical Engineering Faculty, Yildiz Technical University, Turkey, Istanbul
    This study investigates the effective parameters of scuffing failure in gears using the integral temperature method. For this aim, the mass temperature, integral temperature and scuffing safety factor are calculated for a given parameters. Then, integral temperatures are simulated based on various geometrical, operational and lubrication parameters. Obtained results are presented graphically. The obtained results show that increasing the module mn results in a decrease in the integral temperature ϑint. Similarly, increasing the pinion teeth number zp results in a decrease in the integral temperature ϑint. Increasing the module and tooth number positively affects the scuffing failure in gears. In contrast, increasing the transmitted torque MT1T results in an increase in the integral temperature ϑint. Similarly, increasing the pinion speed np increases the mass temperature ϑM, and increasing the lubricant (oil) ϑÖ temperature increases the integral temperature ϑint. Increasing the transmitted torque, lubricant temperature and the pinion speed negatively affects the scuffing failure in gears. Finally, increasing the nominal kinematic viscosity v40 decreases the integral temperature ϑint. Increasing the nominal kinematic viscosity positively affects the scuffing failure in gears. By considering the effective parameters of scuffing failure such as geometrical, operational and lubrication, one can design and manufacture the desired gears without scuffing failure.