Ukrainian Journal of Mechanical Engineering and Materials Science. – 2023. – Vol. 9, No. 1

Permanent URI for this collectionhttps://ena.lpnu.ua/handle/ntb/61131

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, 2023. – Volume 9, number 1. – 70 p.

Український журнал із машинобудування і матеріалознавства

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    Contents
    (Видавництво Львівської політехніки, 2023-02-28)
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    Influence of cutting time on types of oscillations during blade processing
    (Видавництво Львівської політехніки, 2023-02-28) Vnukov, Yuriy; Dyadya, Serhiy; Kozlova, Olena; Trishyn, Pavlo; Zubarev, Andriy; Independent scientist, USA, California; National University “Zaporizhzhia Polytechnic”
    Despite many years of research on the impact of vibrations on the quality of manufacturing parts and tool stability during machining, these problems are still relevant. One of the reasons is uncertainty regarding the pattern of occurrence of types of oscillations during mechanical processing and their effect during cutting. Therefore, the work aimed to determine the patterns of occurrence of types of oscillations during mechanical processing and their effect during cutting. The research was carried out when turning parts according to various schemes. Turning is a universal operation where it is possible to carry out continuous processing, intermittent turning, and different depths of cutting. During the experiments, a special device was used, with the help of which it is possible to provide different dynamic characteristics of the cutter. The cutting modes were chosen so that turning occurs with self-oscillations. With the help of eddy current sensors and an electrical contact device, oscillograms of the technological system's oscillations during cutting were recorded, with the cutting time and spindle turn marked on them. During the continuous turning of a cylindrical part, there are forced oscillations, which are superimposed firstly by the accompanying free oscillations of the technological system, and then by self-oscillations. After the first rotation of the part, the processing is carried out according to the wavy trace of the accompanying free oscillations, which, combined with the phase shift, creates the conditions for self-oscillation occurrence. When turning with a full depth of cut, there are forced oscillations on which self-oscillations are superimposed. When turning a cylindrical part with a groove, the cutter cuts into it with an impact at each turn. At the same time, there are forced oscillations during cutting, which are superimposed by the technological system's accompanying free oscillations and self-oscillations. Due to the wavy trace on the cutting surface, self-adjustment of the self-oscillations occurs in the transition zone after attenuating the accompanying free oscillations. During idling, free oscillations of the cutter take place. When turning an eccentrically fixed part, the cutting depth changes continuously. The excitation source of the forced and accompanying free oscillations is the action of the periodic cutting force. Under such conditions, self-oscillations do not occur. When turning inserts of a limited length during cutting, forced oscillations are applied, which are superimposed by the accompanying free oscillations of the technological system. Despite a wavy cutting surface, there is not enough time for self-oscillations to occur. The conducted studies show that during machining, there is a regularity of the action of the types of oscillated oscillations operating throughout the cutting time. At the same time, the accompanying free oscillations of the technological system are superimposed and act on them for a certain time, after which, due to transient processes, self-oscillations occur until the end of the cutting. Their characteristic features determine the types of oscillations that occur during cutting. When the types of oscillations during cutting are known, measures are prescribed to prevent their impact on the tool's quality of processing and stability.
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    Modeling the influence of the shape of the local heat flow intensity distribution on the surface of a semi-infinite body on the stress state in the vicinity of a subsurface crack
    (Видавництво Львівської політехніки, 2023-02-28) Zelenyak, Volodymyr; Kolyasa, Liubov; Klapchuk, Myroslava; Lviv Polytechnic National University
    A mathematical model to determine the two-dimensional thermoelastic state in a semi-infinite solid weakened by an internal crack under conditions of local heating is examined. Heat flux due to frictional heating on the local area of the body causes changes in temperature and stresses in the body, which significantly affects its strength, as it can lead to crack growth and local destruction. Therefore, the study of the problem of frictional heat is of practical interest. This paper proposes to investigate the stress-deformed state in the vicinity of the crack tip, depending on the crack placement. The methods for studying the two-dimensional thermoelastic state of a body with cracks as stress concentrators are based on the method of complex variable function. Reducing the problem of stationary heat conduction and thermoelasticity to singular integral equations (SIE) of the first kind, the numerical solution by the method of mechanical quadrature was obtained. In this paper, we present graphical dependencies of stress intensity factors (SIF) at the crack tip on the angle orientation of the crack as well as forms of the intensity distribution of the local heat flux. The obtained results will be used later to determine the critical value of the intensity of the local heat flux from equations of limit equilibrium at which crack growth and the local destruction of the body occur. The scientific novelty lies in the fact that the solutions to two-dimensional problems of heat conduction and thermoelasticity for a half-plane containing a crack due to local heating by a heat flux were obtained. This would make it possible to obtain a comparative analysis of the intensity of thermal stresses around the top of the crack, depending on the form of distribution of the intensity of the heat flow on the surface of the body. The practical value is the ability to extend our knowledge of the real situation in the thermoelastic elements of engineering structures with the crack that operate under conditions of heat stress (frictional heat) in various industries, particularly in mechanical engineering. The results of specific values of SIF at the crack tip in graphs may be useful in the development of sustainable modes of structural elements in terms of preventing the growth of cracks.
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    Mathematical modelling of flux-cored layer formation
    (Видавництво Львівської політехніки, 2023-02-28) Kassov, Valery; Vasylchenko, Yana; Berezhnaya, Elena; Malyhina, Svetlana; Donbass State Engineering Academy
    Mathematical model for the calculation of the chemical composition of deposited metal with sufficient accuracy has been developed. The presented mathematical model has been developed taking into account shares of base and clad metal, the metal of the previous roll in the subsequent one, and the relative step of cladding. Based on the calculated composition of deposited metal by flux-cored wire it has been proved and experimentally confirmed that the required chemical composition of deposited metal is achieved in the second-third layer regardless of the surfacing step. Theoretically established and experimentally verified the effective relative step of cladding. The established relative pitch allows for minimizing waste when cladding with flux-cored wire. In this case, the cross-sectional area of the roll reinforcement after the finishing run will be minimal.
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    Investigation of rheological properties of a nanocomposite of superparamagnetic iron oxide nanoparticles with polyethylene glycol
    (Видавництво Львівської політехніки, 2023-02-28) Javanbakht, Taraneh; Concordia University
    This paper presents the results of a new investigation of the rheological properties of a nanocomposite of superparamagnetic iron oxide nanoparticles (SPIONs) with polyethylene glycol (PEG). The surface of the nanocomposite had no electrical charge and the SPIONs were coated with the polymer. The investigations were performed at different temperatures and the results were compared on different rheological parameters. The steady-state behavior of samples was observed at 20 °C and 40 °C and a small increase of viscosity versus shear strain, shear rate or time was revealed at 60 °C. Moreover, the shear stress increase was observed with the increase of shear rate and shear strain. The slopes of the corresponding changes were higher at 20 °C and decreased with the increase in temperature. The torque values increased with shear strain and time. The same phenomenon concerning the different slopes at different temperatures was observed for the torque-shear strain and torque-time variations. These results showed that the rheological properties of the nanocomposite depended on the temperature and could change with the temperature increase. An advantage of this study was that the comparative investigation of the rheological properties of nanocomposite at different temperatures was carried out. The other advantage was that the effect of the coating of the SPIONs with the polymer was observed in the obtained results. This new investigation of the nanaocomposite of SPIONs-PEG coated with PEG can provide comparative data for more investigations of the surface charged SPIONs coated with this polymer. These studies can provide information for a further investigation of the effect of the surface charge of SPIONs in the polymeric matrix on their rheological properties.
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    Reliability prediction of a mechatronic hydraulic drive at the early design stages
    (Видавництво Львівської політехніки, 2023-02-28) Tikhenko, Valentin; Odesa Polytechnic National University
    The article deals with the reliability of technological machines that use hydraulic feed drives. A priority task in mechanical engineering is the design of mechanical systems with higher stability, reliability, and performance. Various mechatronic systems are used to solve this problem, including mechatronic motion modules for hydraulic drives of technological machines. It is noted that the study of the reliability of mechatronic systems presents a special problem since the interaction of mechanical, hydraulic, and electronic systems gives rise to some new aspects of the theory of reliability. The main technical solutions for reliability incorporated in the design directly impact the machine's functional and economic characteristics. When predicting reliability at an early stage of design, there is the greatest uncertainty (entropy) in assessing the possible states of the machine. As an object of study, a mechatronic hydraulic drive is considered an electro-hydraulic motion module, which can be used in feed drives for heavy metal-cutting machines or industrial robots with a large load capacity. An important parametric characteristic of such a drive is the positioning accuracy of the working body, its stability, and the preservation of values within the specified limits over time. A review of the methodology for assessing and predicting the reliability of mechanical systems is carried out. It is noted that several statistical methods require the accumulation of test results for serial models or prototypes, but many important factors may not be taken into account. The purpose of this article is to obtain the results of predicting the parametric reliability of mechatronic hydraulic drives by using the method of expert assessments (rank correlation) at the early stages of design. This method is based on the ability of independent experts (qualified experts in the field) to provide useful information in the face of quantitative uncertainty. When setting the problem of predicting reliability, the factors that affect the positioning accuracy of the hydraulic drive were ranked in order of importance (ranked). An analytical relationship was established between the weight of the factor and its number in the series. The arithmetic mean weight, the mean relative weight, the standard deviation of the factors that affect the parametric reliability of the drive, and the coefficient of variation are determined. The consistency of expert opinions was shown based on heuristic indicators using the concordance coefficient (Kendall criterion). The considered technique can be used to predict and evaluate the reliability of mechatronic systems that are being developed for use in various fields of technology.
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    Simulation and analytical studies of chip formation processes in the cutting zone of titanium alloys
    (Видавництво Львівської політехніки, 2023-02-28) Stupnytskyy, Vadym; She, Xianning; Dragašius, Egidijus; Baskutis, Saulius; Prodanchuk, Oleh; Lviv Polytechnic National University; Kaunas University of Technology
    The low machinability of titanium alloys is determined by the physical, mechanical, and chemical properties of these materials and their mechanical characteristics. It is also evident in the hardened state of the material being processed during cutting and in the initial state. This phenomenon is caused by thermodynamic parameters that determine the properties of titanium material at elevated temperatures. The peculiarities of the cutting and chip formation processes during titanium alloy machining are presented in this article. The peculiarity of the described approach is the analysis of the results of simulation modeling of cutting in Deform 2D software. It is proved that the frictional factor in the formation of the thermal characteristics of the cutting process, which arises as a result of the chip sliding along the tool, dominates the load factor (caused by force and deformation processes in the chip root). It has been established that the length of contact between the chips and the tool’s rake face has a certain tendency to change: the contact length first increases and then decreases with increasing cutting speed. An analysis of the dependence of the chip compression ratio on changes in cutting speed has shown that with an increase in cutting speed, the average value of the compression ratio practically does not change, but the amplitude of its oscillation increases significantly, which is equivalent to a change in the shear angle. This parameter changes dynamically due to the adiabatic nature of chip formation.