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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Browsing Ukrainian Journal of Mechanical Engineering and Materials Science. – 2021. – Vol. 7, No. 1/2 by Author "Lviv Polytechnic National University"
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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 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.