Ukrainian Journal of Mechanical Engineering and Materials Science. – 2021. – Vol. 7, No. 1/2
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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, 2021. – Volume 7, number 1/2. – 62 p.
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Item Laser surface modification of materials(Lviv Politechnic Publishing House, 2021) Pavlovskyy, Yuriy; Ivan Franko Drohobych State Pedagogical UniversityTo develop any process of laser technology, you need to solve 3 problems: 1) What are the properties of the interaction of laser radiation with matter must be selected to achieve the goal (resonant – non-resonant, absorption-scattering, photo- or thermal absorption, heating, hardening, melting, softening, evaporation, decomposition, coagulation, etc.); 2) What type of laser source should be used to achieve this goal (wavelength, operation mode – continuous or pulse frequency, power, pulse duration, transverse energy distribution in the beam, coherence, monochromaticity, polarization, etc. taking into account the reliability, stability of the process and its value, and how to calculate and verify these parameters ?; 3) What are the requirements for the transverse and longitudinal shape of the beam and what opto-mechanical, opto-electronic and other systems are needed to solve this problem? Successful solution of these problems hardens the high quality of the result of the application of laser technology of materials processing. The aim of this work is to show the effectiveness of laser surface treatment of materials on their micromechanical properties. The surface of the samples was treated with laser radiation using a pulsed neodymium laser YAG: Nd. Vickers microhardness measurements were then performed. The surface of silicon carbide was irradiated with a laser beam with different technical parameters. The micromechanical characteristics of the treated samples were studied and their comparison with the source material was made. Suggestions for laser modification of mechanical properties of superhard materials are made. Alloying of aluminum with titanium nitride impurities by pulsed laser irradiation was performed. A significant increase in microhardness in the field of laser fusion of titanium nitride nanopowder into the aluminum matrix was revealed. We have thus shown that laser treatment of structural and functional materials is an effective method of controlling their properties. A set of experimental studies, in particular, structural, optical, and magnetic, will be conducted to physically substantiate the established results. In this paper, we have expressed our views, citing well-known literature sources.Item Design – technological optimization of the level of residual deformations during welding of pipe sections from PT-7m alloy(Lviv Politechnic Publishing House, 2021) Biloborodchenko, Volodymyr; Dzyubyk, Andrij; Dzyubyk , Liudmyla; Lviv Polytechnic National UniversityApplication of tubular elements in the chemical industry is widely used. The special properties of materials and their reaction to the welding thermal cycle is quite complex. This is especially true of titanium alloys, which when heated are sensitive to environmental influences, require special welding techniques and undergo residual welding deformations. The welded joints of tubular elements made of titanium alloy brand PT-7m, which undergo transverse deformations due to welding, are studied. It is necessary to ensure high-quality sealed welds. Analysis of the literature has shown that to obtain a guaranteed penetration it is necessary to increase the power of the arc discharge or perform multi-pass welding. This will provide larger cross sections of welded parts and should provide the specified strength characteristics. However, this technology, in turn, leads to an increase in residual deformation in the vicinity of the welded joint due to the intensive increase in the coefficient of linear expansion when heating the material. Also, the special thermophysical properties of titanium alloy such as increasing the affinity for gases when heated, increasing the grain size lead to a decrease in strength properties. In the presented work it is proposed to use a mechanical angular deformer with an indicator head and a reference base for the study of transverse residual deformations. Peculiarities of measuring sockets and methods of their preparation are revealed. A calculation scheme for determining the amount of deformation has been developed, which has been tested on flat welded specimens and transferred to tubular elements. The sequence of deformation measurement process is described and the peculiarities of their formation on flat samples and tubular sections are studied. The constructive decision of a welded joint of pipes which provides use of a compensation ring is offered. This approach allows to provide reliable protection of the root of the seam and its optimal formation with minimal residual deformation. At the same time it is possible to reach the reproducible form of a dagger of similar penetration in one pass. The result is a welded joint of the lock type, which is sealed and has a free formation of the seam root with high-quality protection by the gas atmosphere. The use of pulsed arc welding with a non-fusible electrode in an argon environment with filler wire allows to minimize the thermal impact on the base metal. Statistical processing of experimental data on the parameters of the welding mode and their influence on the residual transverse welding deformations is carried out. To obtain an unambiguous statistically reliable answer about the valid law of distribution of experimental data of the results of strain measurement, the balancing procedure and the development of an analytical pproximation distribution model are involved. It is shown that the measured values of the residual transverse deformation of the welded assembly are correctly described by the Laplace distribution, which predicts (probability not worse than 90 %) a decrease in the average value of the deformation value by 1.3 times.Item Analysis of environmental hazard parameters of the workplaces in steel plants in Nigeria(Lviv Politechnic Publishing House, 2021) Saheed, Babatunde Lateef; Adeshina, Bamidele Kayode; Bello, Bashir Olawale; Obajemihi, Obafemi Ibitayo; Department of Mechanical Engineering, University of Ilorin; Department of Mechanical Engineering, Dangote Cement Plc; Department of Food Engineering, University of Ilorin; School of Food Science and Engineering, South China University of TechnologyThe steel plant’s workplace environmental hazard parameters in Ilorin, Nigeria was evaluated using response surface methodology (RSM). Three environmental parameters (illumination, temperature and noise level) were measured. The data obtained were compared with the Occupational Safety and Health (OSHA) standard for the workplace environment. Based on the preliminary analysis of the workplace environment, five variables (No. of lightings, no. of windows, no. of machines, no. of workers and age of machines) were considered as input parameters. RSM was used to perform the modelling and optimization to identify functional relationships between the input and output parameters. Three (3) model equations one for each of the output parameters were developed and checked for adequacy and validity. All developed model equations were found to present functional relationships between input and output parameters. Hence, all developed model equations can be used as reliable tools for estimating, predicting, and conducting analysis for workplace environmental hazard. Best optimized results were selected based on desirability (0–1). Illumination, temperature and noise level got desirability rate of 0.921, 1.000 and 0.983 respectively. The outcome of this study suggested that the environmental parameters studied within the workplace do not conform with the OSHA standard and as a result may constitute long-term health risks to the workers.Item Investigation of rheological properties of graphene oxide and its nanocomposite with polyvinyl alcohol(Lviv Politechnic Publishing House, 2021) Javanbakht, Taraneh; Department of Physics, Concordia University, Richard J. RenaudThis paper focuses on the rheological properties of graphene oxide (GO) and its nanocomposite with polyvinyl alcohol (PVA). The purpose of this paper is to compare the mechanical properties of these materials. GO is a nanomaterial that has been widely studied in engineering. The comparison of its rheological properties with those of its nanocomposite with PVA has been required. Rheology is an appropriate method for the comparative investigation of the mechancial behavior of these materials. The challenge has been to compare the rheological parameters of these materials regarding their mechanical properties. This investigation shows that GO and GO-PVA do not exhibit the same viscosity change at low shear rates. While GO shows a significant decrease of viscosity, GO-PVA shows a steady state behavior at these shear rates. However, both GO and GO-PVA show a constant viscosity at high shear rates. These materials show the same behavior concerning the change of their viscosity versus shear strain or time. The changes of torque versus shear strain and time for GO and GO-PVA are representes as increasing curves and lines, respectively. The increase of shear stress versus shear rate or shear strain coincide for both materials. Powever, as expected, the first change represents an increasing line and the second one a curve. This original investigation shows the difference between the mechanical behaviour of GO and GO-PVA concerning the change of their viscosity at low shear rates and their similarity at high shear rates. Moreover, this study gives new results concernig the change of other parameters as described above. The unique physicochemical properties of GO have made it an important candidate in engineering and materials science. This investigation can lead to a better understanding of the rheological properties of GO and GO-PVA for the improvement of these applications.Item Review and complement of methods for changing the movement speed of mechanisms and machines elements(Lviv Politechnic Publishing House, 2021) Strilets, Oleh; Malashchenko, Volodymyr; Kłysz, Sylwester; National University of Water and Environmental Engineering; Lviv Polytechnic National University; Airworthiness Division, Air Force Institute of TechnologyIn mechanical drives of machines there is a need to control changes in the speed of their actuators. Stepped and stepless gearboxes are used for this purpose. Known speed control devices have many disadvantages that adversely affect the durability and reliability of drive components and machines in general. These include the design complexity, high material consumption, automation complexity, dynamic loads during transitions from one speed to another, intensive wear of parts due to the friction connections use. The purpose of the work is to develop an algorithm for determining the kinematic, power parameters and dimensions when designing speed change devices through the ring gear of a gear differential with a rotary stopper in the form of a closed-loop hydraulic system based on authors’ previous computer-theoretical research and classical scientific advices. To solve these problems analytical expressions and graphs have been obtained for the relationship between speeds of gear differential links, the efficiency has been determined by the method of potential power – based on friction losses in each gearing. With the help of computer modeling of analytical expressions, using the MATLAB software, graphical dependences of efficiency have been obtained, which made it possible to evaluate the accomplishment of the gear differential in terms of energy consumption and possible selfbraking. Based on Lagrange's theory, a dynamic model of a speed change device with a ring gear control has been constructed and a solution of the obtained system of equations has been proposed. The 3D modeling of the device has been executed and at the final choice of the optimum variat of model, after some specifications, development of technical documentation can be started. The results obtained have practical application at the stage of development and design of new speed control devices through the ring gear, allow to evaluate the operation of gear differentials in terms of energy consumption and self braking and are the basis for further research. The graphical dependences obtained for the efficiency of the gear differentials clearly allow us to trace the change in the value of the efficiency depending on the angular velocity of the ring gear and the gear ratio. For the first time, analytical expressions were obtained to determine the efficiency of the gear differential of a speed-changing device with a driving sun gear, driven carrier, or vice versa, more accurately. The resulting graphical dependences for efficiency visually allow to trace change of efficiency value depending on angular speed of a ring gear, as a control link, and the gear ratio. Results are ecommended for introduction into design and engineering practice at development of designs of speed change devices through differential gears of drives of various equipment and in educational process of higher technical educational institutions in discipline of mechanical engineering. Areas of further research – improvement of speed change devices through gear differentials in the design, manufacture, operation and repair.Item The effects of infill patterns on the mechanical properties of 3D printed PLA parts fabricated by FDM(Lviv Politechnic Publishing House, 2021) Eryildiz , Meltem; Faculty of Engineering and Architecture, Beykent UniversityThe purpose of this study is to analyze the effect of the infill pattern on the mechanical properties of 3D printed PLA parts. Polylactic acid (PLA) parts were fabricated by fused deposition modeling (FDM) at various infill patterns at 30 % infill density. Five different infill patterns (stars, 3D honeycomb, honeycomb, gyroid, Hilbert curve) have been investigated. The results have shown that the honeycomb infill pattern exhibited the highest mechanical properties with 29.43 MPa and 2.04 mm elongation due to the improved strength of the strut junctions in this pattern. In the case of the Hilbert curve pattern, compared to the other patterns, though they have the same infill density, tensile strength was lowest because of the presence of large air gaps in the pattern that induced rapid fracture during the test. The optical microscope images of the fracture surfaces were compatible with the tensile strength results. Also considering the build time and the spent filament, it can be said that the honeycomb infill pattern is very promising. Lastly, the results showed that the tensile strength and elongation of 3D printed PLA parts increased 43.4 % and 32 %, respectively, under optimum infill pattern conditions. The findings of this study will help manufacturing firms and researchers to decide on the appropriate infill pattern, so that FDM parts can be fabricated with minimal production cost and good mechanical properties.