Ukrainian Journal of Mechanical Engineering and Materials Science. – 2022. – Vol. 8, No. 2

Permanent URI for this collectionhttps://ena.lpnu.ua/handle/ntb/60074

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, 2022. – Volume 8, number 2. – 76 p.

Український журнал із машинобудування і матеріалознавства

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    Analysis of thermal comfort models of users of public urban and intercity transport
    (Видавництво Львівської політехніки, 2022-02-22) Yakovenko, Yevheniia; Voichyshyn, Yurii; Horbay, Orest; Lviv Polytechnic National University
    Regardless of the vehicle's application, the thermal comfort of the vehicle's occupants and driver is given increased attention. Maintaining a sense of thermal comfort, whether for safety, health or occupant thermal well-being reasons, is one of the most important goals of heating, ventilation and air conditioning (HVAC) systems. There are a significant number of physical variables that affect thermal comfort. Therefore, evaluating thermal comfort has always been a complex issue and has attracted the attention of researchers. The feeling of thermal comfort is provided by factors that depend on the heat exchange between the human body and the external environment. It is well known that one of the requirements to be fulfilled is to find a person in thermal neutrality in the environment according to the comfort equation. The article describes and evaluates the following indicators: DTS (dynamic thermal sensitivity), TS (thermal sensitivity), PMV (predicted mean voice) and PPD (predicted percentage of dissatisfaction). The most common models for evaluating thermal comfort, namely the Predicted Mean Vote (PMV), Taniguchi’s model, Zhang’s model and Nilsson’s model in a variety of car cabin conditions, have been reviewed. The limitations of these models in terms of the objectivity of the results obtained are analysed.
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    Contents
    (Видавництво Львівської політехніки, 2022-02-22)
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    Strengthening and reconstruction of drilling core pipe for engineering and geological exploration
    (Видавництво Львівської політехніки, 2022-02-22) Dzyubyk, Andrij; Dzyubyk, Liudmyla; Shpak, Bohdan; Lviv Polytechnic National University
    Currently, there is a tendency to increase the depth of gaseous and liquid fossils extraction. Therefore, prospecting and developing new deposits is promising. There is also a need to create new freshwater sources and implement relevant geological work based on this need. It is essential to have information about the characteristics of the explored slabs and the geology of the fields in general. Implementation of engineering and geological core drilling exploration is the most acceptable and provides the necessary data. Here, the peculiarities of the technological schemes of the process implementation make it possible to obtain separate sections of structures at a depth of the drilling equipment. It is essential to use traditional equipment, recommended for decades and provides the necessary results [1–3]. In the drilling process, you can achieve different diameters and depths of wells execution, obtain fossil samples etc. Engineering and geological exploration drilling is now taking on increased use in various industries [3]. Therefore, the problem of providing highquality drilling tools, the stability of their operating characteristics, and the possibility of usage in different conditions is an urgent need today. Modern drilling problems determine the usage of components of the core set with the appropriate physical and mechanical characteristics. Especially it relates to elements close to the drilling tool and the place of fossil; destruction – drill pipe. It is installed immediately after the crown core drill and receives almost the same loads and effects during working [1–3]. Conditions for the implementation of the process of core drilling are characterized primarily by the effect on the elements of the significant axial and twisted core set forces. There is the influence of the corrosive and active environment of the fossil in the washing and lubricating liquids well, etc. High temperatures are also observed at the drilling sites [3], which negatively affect the working tool and speed up its operation. As a result, there is an intensive shock, and abrasive core pipe wear and operation indicators change their constructive size. As a result, it is necessary to replace the operated drill string periodically. Considering modern technical and economic factors, it may be decided to repair a pipe to its original size in many cases. There are tasks for providing the appropriate characteristics of the core pipe surface. It is possible to model such properties of the new surface that functionally the best meet the conditions of the drilling process of a given geological formation. The peculiarities of applying the therapeutic layer on the surface of the core pipe are investigated in work. The experience shows that using electric arc surfacing under the flux layer is expedient. This provides the necessary adhesion of the applied layer and promotes obtaining resistance to the operation surface of the core pipe. At the same time, there is high-quality protection and the possibility of additional alloying through the flux-slaggy welding bath. Using electrode powder type wires creates conditions for flexibility to achieve the established characteristics of functional layers [4–6]. The filling flux, located in the cross-section of the electrode wire, can be easily changed by chemical composition. At the same time, it is possible to make relatively small parties of a wire with the set characteristics. The technological scheme justification about the core pipe surfacing is performed. It provides the previous displacement of the electrode butt size from the zenith of the core pipe to prevent the welding bath from spreading. The structural pipe size , the requirements for residual deformations, and the conditions of shapping the welded layer show the practicality of welding on a helix.
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    Algorithm of machine creation using the mechanism of articulated disjunction
    (Видавництво Львівської політехніки, 2022-02-22) Zinko, Roman; Hlobchak, Mykhailo; Beshley, Andiy; Pitrenko, Oleksiy; Lviv Polytechnic National University; National Aerospace University “Kharkiv Aviation Institute”
    Problem statement. Any methodology is based on knowledge about the problem. The fullness and orderliness of the base determine further volumes and possible options for implementing the methodology. Purpose. To analyze the existing ways of machine creations and propose the new effective algorithm of machine creation using the mechanism of articulated disjunction. Considering the research structure and improvement of the informational and program technologies, changes to the traditional methodology of machine creation are made. The existing paradigm: parametric and functional performance of the machine, the design of which is improved based on existing machines, is a modification of predecessors' parametric and functional performance. Proposed paradigm: parametric and functional performance of the new machine, improved based on the subject area of technical solutions, methods of design and operational conditions more precisely coincide with the technological process to realize what they are called. Proposed hypothesis: there are such methodologies of design that provide an opportunity to provide rational productivity within existing operational conditions. Methodology. Morphological space is used to form qualitative features of the created machine. The peculiarity of the proposed methodology is that the set of features of the created machine also contains subsets of processes and phenomena in which the machine is involved. This allows assessing the compliance of the process in which the machine is involved and the machine operation processes. Findings (results). The algorithm of machine creation using the mechanism of articulated disjunction is proposed. It allows the creation of the new construction at a given sequence of stages to improve at every step in a given direction based on the determined criteria. Originality (novelty). Method of articulated disjunction, which is based on the principle of formation of the set of necessary properties of the structural elements of the machine based on a given primary criterion of machine efficiency. The essence of the method of articulated disjunction is that the sample of elements that have common features and properties is reformulated based on a given criterion. The proposed method provides an opportunity to determine the advantages of one structure described by various factors, in comparison with others, based on the criterion set. Practical value. The algorithm of synthesis and improvement of existing machines allows for determining their main quality features in the initial stages of the design of machines.
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    Approximate calculation of natural frequencies of oscillations of the plate with variable cross-section of the discrete-continuous inter-resonance vibrating table
    (Видавництво Львівської політехніки, 2022-02-22) Lanets, Oleksii; Maistruk, Pavlo; Maistruk, Volodymyr; Derevenko, Iryna; Lviv Polytechnic National University
    Problem statement. To ensure highly efficient inter-resonance modes of operation of vibrating equipment, the oscillating masses of the system must have certain inertia-rigid parameters, as well as a certain frequency of natural oscillations. The disadvantage of highly efficient inter-resonance oscillatory systems is that the third reactive mass must be small, and therefore the use of complex and large structures is impossible. Therefore, it is best to use the reactive mass as a continuous section. The continuous section, which is a flexible body, optimally combines inertial and rigid parameters. Scientific works have already considered the design of the vibrating table, in which the continuous section is an ordinary rectangular plate hinged in the intermediate mass. This decision looks quite promising. However, likely, the rectangular shape of the plate is not the best option to ensure maximum energy efficiency. Purpose. Extend the method of calculating the natural frequency of oscillations of the plates by the approximate Rayleigh-Ritz method using the general hyperboloid equation to plates with variable cross-section for the proposed types of plates and check the results with the calculation in Ansys software. Methodology. The calculations of the plates were performed using the basic principles of the theory of oscillations, in particular the Rayleigh-Ritz method in the software product MathCAD. Findings (results) and originality (novelty). Two types of elastic plates with variable cross-sections are considered. In the first case, the shape of the plate was given by quadratic functions, in the second case, it was described by trigonometric functions of cosine. In both cases, the same conditions of attachment in the intermediate mass were observed. The calculation of the first natural frequency of oscillations of the considered plates was performed using the approximate Rayleigh-Ritz method with the assumption that the deflection of the plates occurs on the surface of the hyperboloid. The reliability of the obtained results was verified by numerical calculation in the software product Ansys. Practical value. It is assumed that the proposed types of plates can increase the dynamic potential of the vibrating machine. Scopes of further investigations. For further study of the considered types of plates as a continuous section of the inter-resonance vibrating machine, it is necessary to calculate their deflections at forced oscillations.
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    Influence of the velocity of the medium layer on its dynamic parameters in the process of vibration separation
    (Видавництво Львівської політехніки, 2022-02-22) Rebot, Dariya; Babii, Artom; Lviv Polytechnic National University
    A review of recent research in the field of vibration separation of bulk media has been done. It was found that the productivity of the separation process is influenced not only by the design characteristics of the vibrating separator, in particular the length, angle and capacity of the working housing, but also the dynamic processes that occur in bulk medium during separation. The efficiency of the separation process significantly depends on the mutual influence of the velocity of the bulk medium along the separator sieve and its amplitude-frequency characteristics. Based on the review, the relevance of further study of these parameters was established. Using the methods of nonlinear mechanics, a mathematical model of the motion of the layer of bulk medium on the sieve of the vibrating separator was built. The layer of bulk medium was modeled by an elastic beam, which is in contact elastically, rigidly, or as hinged. Graphical dependences of the influence of the frequency of external perturbation and the velocity of the bulk medium along the sieve of the separator on its oscillation amplitude were obtained. The obtained mathematical model and graphical dependences showed that small velocities of the medium layer lead to an increase in the amplitude of oscillations of the bulk medium and a decrease in its frequency of oscillations, which increases the permeability of medium particles and increases the productivity of the separation process. The obtained researches allow us to increase the efficiency of the separation process, to regulate the processes that take place in the bulk medium and to increase the speed of its passage through the sieve openings. The constructed mathematical model can serve as a basis for further studies of the influence of changes in the physical and mechanical characteristics of the bulk medium on its dynamic parameters in the process of vibration separation.
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    Study on microstructure characterization of fracture frontier of post welds heat treatment and type IV cracking of P92 steel welded joinT
    (Видавництво Львівської політехніки, 2022-02-22) Pal, Vinay Kumar; Singh, Lokendra Pal; Sam Higginbottom University of Agriculture, Technology And Sciences Allahabad
    In the research work presented in this study microstructure evolution at fracture frontier of crept P92 weld, creep rupture life and effect of creep exposure time on microstructure evolution in fine-grained heat affected zone were performed. Microstructure evolution and creep rupture behavior of metal arc welded joint of P92 steel plate in the as-welded have been studied. The different states of post weld heat treatment (PWHT). (i). post welded heat treatment at 760 °C for the 2h (ii). re-austenitizing at 1040 °C for 60 min and air cooled and tempering at 760 °C for 2h. In PWHT condition, most common type IV cracking was observed creep exposure 620 °C / 150 MPa. The martensitic matrix fracture is also observed in PWNT 1 condition. A move away from the fracture frontier, the cavities still remain in the microstructure while the martensitic matrix fracture is difficult to observe. The line mapping also confirmed the increase in weight percentage of Cr and Mo in M23C6. The elemental mapping of PWHT 2 condition is also carried out in FGHAZ which confirm the formation of Mo and Cr-rich M23C6 precipitates.