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ISSN 2522-4255 (Online) ISSN 2521-1943 (Print)

The purpose of the international science-and-technology journal "Mechanics and Advanced Technologies" is to familiarize scientists worldwide with the latest advances in the field of mechanical engineering as well as with the scientific research in the field of advanced computational methods and design methodology in mechanical engineering.
We welcome scientists, scientific and technical experts in the field of mechanical engineering to collaborate with us on expanding the horizons of science.

The international science-and-technology journal "Mechanics and Advanced Technologies" is the successor to the reader in mechanical engineering "Journal of Mechanical Engineering NTUU "Kyiv Polytechnic Institute" (ISSN 2305-9001, e-ISSN 2409-5966)

Founder: National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute".

Frequency: 3 issues a year.

We accept papers in following languages: English, Ukrainian, Russian.

Cite the title as: Mech. Adv. Technol.

Обновлено: 2 дня 9 часов назад

Тhe operability analysis of spindle-motor hybrid electromechanical systems

ср, 06/23/2021 - 00:00

Motor-spindles are belong to a special class of complex dynamic systems of natural and natural-anthropogenic origin, which can be realized both translational and rotational motion, and represent a variety of developing species. Such systems are used in metalworking complexes, lathes, milling, drilling, grinding, multi-purpose and other machines. In modern designs of spindle units rolling bearings, hydrostatic, hydrodynamic, gas-static (aerostatic), gas-dynamic (aerodynamic), magnetic bearings and their combinations (hybrids) are used, for example, gas-magnetic (gas-static bearings with a magnetic suspension that allows to provide rotational frequencies) up to 10-20 thousand rpm, and in drilling and milling and grinding up to 100-200 thousand rpm and above. With the further development of technology in the machine-building industry, motor-spindles began to appear, which are able to realize the movement of the feed by means of gears and couplings, using pneumatic systems. They are also able to realize the movement of in using hydraulic systems, using screw gears. The design concepts of hybrid and combined the motor spindles, received by results of structural anticipation on the basis of use of innovative synthesis methods of hybrid electromechanical systems are considered. Results of mechanical calculations of rigidity and electromagnetic calculations are presented in the article.  On the ground of the calculation data the operability analysis of the electromechanical systems of motor spindles is made. To develop a morphological model, functional features were selected, which are systematized and divided into three groups in accordance with the modular principle.

Research into ultrasoic and hydrodinamic cavitation phenomena in a hydraulic system

ср, 06/23/2021 - 00:00

The article describes the course of the ultrasonic cavitation in a hydraulic tank and the hydrodynamic cavitation in a gear pump. The course of those phenomena was confirmed in experimental tests carried out with the use of a tank and a pump made of transparent plastics. It has been proved that the oscillator-cavitation system made according to the original project is useful to induce the phenomenon of ultrasonic cavitation. It has also been shown that the PIV visualization method, consisting in a special system of illuminating transparent objects and recording the flow through those objects with a fast camera, is useful for the studying of the cavitation phenomena.

A visible interaction between the ultrasonic and the hydrodynamic cavitation was observed. The induction of ultrasonic cavitation in the tank causes degassing of the oil, and the degassed oil supplying the pump reduces the hydrodynamic cavitation in its internal channels and clearances. This is an example of beneficial effects of the ultrasonic cavitation on the operation of a pump and a hydraulic system.

The presented work is an example of effective co-operation between the communities of Wroclaw University of Science and Technology and Igor Sikorsky Kiyv Politechnic Institute, National Technical University of Ukraine.

Flat surfaces machining by the magneto-abrasive method with permanent magnet end-type heads 3. The influence of the types of the working heads on the effectiveness of the magneto-abrasive machining

ср, 06/23/2021 - 00:00

Investigations of the magneto-abrasive machining (MAM) process of ferromagnetic flat surfaces by three types of end heads were carried out. The nature of the change in the magnitude of the magnetic induction in the working zones was determined. The influence of technological parameters of the machining process was investigated, such as the feed rate of the working heads, the frequency of their rotation about their axis, the size of the working gaps on the change in the parameters of the microroughness of the machined surfaces - Sa, Sp, Sv, the frequency distribution of heights microroughness and size of the supporting surface of the profile. It was shown that the level of roughness achieved after MAM is practically the same and does not exceed, under rational conditions of the MAM process, the values Sa = 0.05-0.07 μm, Sp = 0.2 μm and Sv = 0.39 μm with the only difference that the MAM process by the heads of the "brush-half of torus" type are being realized with increased productivity, especially in terms of reducing waviness and individual elements of the heredity of machining, determined by such factors as depth and feed rate during milling. The kinetics of the formation of a microprofile of surfaces is shown under various technological conditions of the MAM process.

Impoving the quality of products created by additive technologies on the basisi of tig welding

ср, 06/23/2021 - 00:00

The paper deals with the issues of obtaining the minimum waviness of surfaces formed by additive processes of TIG welding. It is known that the geometric parameters of the melt bead, which form a reproducible workpiece layer by layer, are determined by both the energy and kinematic characteristics of the process. In this case, the laying of the rollers occurs with optimal overlap, as a result of which it is possible to achieve the maximum density of the model, however, with the simultaneous appearance of a certain waviness due to thermodynamic phenomena in the melt bath. The proposed model of the formation of a bead of melt, the use of which made it possible to establish the rational conditions for laying out the layers. Experimental studies of the process of argon-arc surfacing of models of a given, regression equations for determining the controlled waviness parameter are obtained.

It is shown that the waviness parameter is influenced by dynamic phenomena and wave processes that develop under the action of a system of forces during the formation of a melt bead. An improvement in the quality of products is seen in the optimization of the methods of forming the rollers, in ensuring the dynamic stability of the movement of the working head, ensuring the appropriate overlap of the trajectories of movement along the layers of the layout by an amount of 0.5e, establishing a rational arc length, and maintaining the dynamic stability of the arc burning.

The response surfaces of the objective functions in the planes of the process parameters are constructed, which provide a clear illustration of the dependence of the controlled geometric parameters on the welding modes.

Stamping a medium – sized cartridge blank from low – carbon steel

ср, 06/23/2021 - 00:00

The work is devoted to obtaining a mediumsized cartridge blank from low-carbon steel. The sequence of punching transitions includes a hot back- extrusion operation, two cold drawthinning operations, and a cold crimp operation. Modeling using the finite element method established: efforts and specific forces during operations, thermal effect during shaping, shape and size of semi – finished products with distributions of strain intensity. An elastoplastic metal model was used, which made it possible to reveal the forces of extracting the tool from deformed semifinished products and the forces of removing semifinished products from the matrix. A hollow semifinished product with the required dimensions of a protrusion on the bottom part from the side of the cavity and a protrusion on the end for forming a flange is obtained by reverse extrusion. The possibility of carrying out the first drawing operation with thinning through three sequentially located matrixes is shown. After this operation, annealing of the semi-finished product is required to restore plasticity. In the second operation of drawing with thinning and additional stamping of the bottom part, the final dimensions of this part from the side of the cavity and the shaping of the flange on the lateral surface of the semi-finished product are provided with the creation of a macrostructure to ensure the required operational properties. The shape and dimensions of the wall of the semi-finished product after the second drawing, the distribution of the intensity of deformations in it are determined from the condition of reaching the final dimensions and mechanical properties of the cartridge blank at the last crimping operation. For this, the deformations obtained as a result of the second drawing are taken into account when modeling the crimp. The proposed technology for stamping a blank of a sleeve can be implemented on a universal pressforging equipment, has a high productivity and minimizes mechanical processing.

Repeatability of multipass laser forming of sheet materials

ср, 06/23/2021 - 00:00


Laser forming (LF) of sheet material is a progressive treatment process and have some benefits. Laser forming is a flexible process and need no heavy metal-intensive equipment and tools. Materials with high rigidity, brittle, elastic materials can be treated by laser forming. Therefore, the investigation of LF is important task. An important point to study is repeatability of multipass laser forming of sheet materials and explore of the possibilities of stabilizing process parameters. Actually, this research is aimed at these issues.

Methods and results of experimental investigation of repeatability of multipass laser forming of sheet materials on parallel and multidirectional passes are described.

A methodical approach of using the VisualWeld software package for modeling the process of multi-pass laser forming has been developed. The mentioned software package was used for modeling as an alternative to a physical experiment to predict sample deformations and determine treating parameters. It has been experimentally established that the repeatability in laser forming is quite high, the difference in the amount of deformation preferably did not exceed 5%. In addition, it is shown that by varying the direction of irradiation trajectories, their step and the number of passes on each trajectory, it is possible to obtain a complex spatial configuration of the product.

Modeling the material of the cylindrical work with welded seam at compression distribution of vehicle parts

ср, 06/23/2021 - 00:00

It is shown that the distribution of the ends of tubular billets, which are the main connecting elements of the vehicle brake system, is accompanied by a loss of stability in the circumferential and axial directions, as well as localization of deformations, followed by destruction in the form of a longitudinal crack that occurs at the end of the preform. The presence of the weld complicates the general conditions of deformation during crimping and distribution and leads to the destruction of the workpiece along the weld. To prevent cracking, it is necessary to tighten the crimping and distributing factors, which inevitably leads to an increase in the number of transitions, the complexity of the process and the cost of manufacturing the part as a whole. The issue of deformation of welded structures is of interest with the development of new materials for the automotive industry, such as joining two or more steel sheets with different mechanical properties, thickness or type of coating, which are important for reducing weight, minimizing costs and reducing scrap. It is shown that the deformation of the pipe billet will depend not only on the plasticity characteristics of the base metal and the weld metal, which is obvious, but also on the ratio of the squares of the pipe billet. The increase in the above modulus of plasticity is accompanied by hardening of the welded joint compared with the initial metal of the workpiece, respectively, a decrease in the value of the secant modulus in both directions – a decrease in the strength characteristics of the weld metal. Further analysis of the deformation of the welded workpiece should be carried out taking into account the local anisotropy caused by the welding seam, which will make it possible to determine the conditions of sustained plastic deformation and create an additional effect on the weakened area.

Increasing the durability of cylindrical parts of wheelcarms of railway

ср, 06/23/2021 - 00:00

A description of a new design of a vibrating machine for strengthening the surface plastic deformation of cylindrical long parts, in particular stabilizers of wheeled carriages of railway cars, is given. The main design and technological parameters of the process of vibration – centrifugal strengthening of these parts are outlined. The influence of technological parameters of this hardening process on such basic indicator of hardening processing as depth of hardening is experimentally investigated on cylindrical samples from 45 steel. Mathematical dependences for the choice of optimal values of design and technological parameters of this hardening treatment are given.

The list of long cylindrical parts for which vibration – centrifugal strengthening treatment is suitable and effective is outlined, among which torsion shafts of suspension of military tanks, axles of wheels of railway transport, drilling and casing pipes of gas and oil wells.

Restoring bearing capacity of fiberglass overwrap of aviation cylinders for storing liquids, gases and fire – extinguishing compounds

ср, 06/23/2021 - 00:00

The article proposes a methodology for numerical research of stressed condition (SC) of aviation cylinders for storing liquids, gases and fireextinguishing compounds in order to determine structural and technological parameters (STP) for repairing of defects in their fiberglass overwraps (FO) due to longterm operation and mechanical damages.

Structural and technological parameters for repair of FO using fiberglass bandages and fiberglass fabric patches аre determined on the examples of numerical research of SC of cylindrical and spherical cylinders.

According to developed methodology, STP for repairing of FO of cylinders make possible to select modern materials and technolognogical equipment.

Application of Avinit vacuum plasma technologies Avinit to the manufacture of high-precision full-size gears

ср, 06/23/2021 - 00:00

Avinit duplex technologies have been developed, combining Avinit N plasma nitriding of finished high-precision parts with subsequent application of Avinit superhard antifriction coatings in a single technological process

Due to the absence of a brittle layer on the nitrided surface after precision nitriding, the preservation of the original geometric dimensions that do not require further mechanical refinement, and the compatibility of the processes of plasma precision nitriding of Avinit N and the vacuum plasma deposition of functional coatings Avinit C, duplex technologies allow the deposition of strong adhered, high-quality coatings.

The effect of the duplex process on the dimensions of parts during plasma nitriding of high-precision gears and the application of Avinit C functional coatings was investigated, the properties of the nitrided layer and the parameters of Avinit coatings were studied.

Plasma precision technology Avinit N allows nitriding of finished parts without changing dimensions, including gears of 4 degrees of accuracy. Avinit N nitriding time is 2 ... 4 times less than with gas nitriding.

The coating of Avinit C310 parts increases the microhardness of the surfaces of the parts and reduces the coefficient of friction, while it has sufficient adhesion to the working surfaces of the gear teeth and bearing raceways.

Manufacturing of high-precision gears with accuracy grade 4 using Avinit duplex technologies was carried out.

Analysis of the results shows that, within the measurement accuracy, no changes in the profiles of the teeth, their location on the ring gear, as well as the location of the gear ring relative to the measuring bases are observed.

Plasma nitriding makes it possible to reduce the nitriding time by more than two times compared to gas nitriding, while the thickness of the layer of the brittle phase with the maximum surface hardness is ensured within the specified values ​​to ensure the necessary indicators of contact and bending long-term strength in the manufacture of gears according to the degree of accuracy 4 without grinding after nitriding.

Measurements of the ring gear after nitriding and coating showed that there were no changes in the geometry of the gear processed by duplex technology. Avinit C310 anti-friction coating 1.5 microns thick does not distort the geometry of the tooth profiles. All parameters of the ring gear manufactured using the Avinit duplex technology correspond to accuracy grade 4 in accordance with the requirements of technical documentation.

The gears manufactured using the Avinit duplex technology were tested as part of the AI-450M engine reducer at the Ivchenko-Progress hydraulic brake stand according to the program of equivalent cyclic tests. A pair of experimental gears were installed in the engine reducer instead of the serial wheels of the second stage of the reducer. The total test time of the wheels was 26 hours. After testing, no damage to the gear, including the Avinit coating, was found. Antifriction coating Avinit C310 with a thickness of 1.5 microns does not distort the geometry of the tooth profiles during testing as part of the AI-450M engine reducer. Measurement of the parameters of the teeth showed a complete absence of wear.

Application of exponential functions in weighted residuals method in structural mechanics. Part II: static and vibration analysis of rectangular plate

ср, 06/23/2021 - 00:00

The paper is continuation of our efforts on application of the properly constructed sets of exponential functions as the trial (basic) functions in weighted residuals method, WRM, on example of classical tasks of structural mechanics. The purpose of this paper is justification of new method’s efficiency as opposed to getting new results. So, static deformation and free vibration of isotropic thin – walled plate are considered here. Another peculiarity of paper is choice of weight (test) functions, where three options are investigated: it is the same as trial one (Galerkin method); it is taken as results of application of differential operator to trial function (least square method); it equals to the second derivative of trial function with respect to both x and y coordinate (moment method). Solution is considered as product of two independent sets of functions with respect to x or y coordinates. Each set is the combination of five consequent exponential functions, where coefficient at first function is equal to one, and four other coefficients are to satisfy two boundary conditions at each opposite boundary. The only arbitrary value in this method is the scaling factor at exponents, the reasonable range of which was carefully investigated and was shown to have a negligible impact on results.

Static deformation was investigated on example of simple supported plate when outer loading is either symmetrical and concentrated near the center or is shifted to any corner point. It was demonstrated that results converge to correct solution much quickly than in classical Navier method, while moment method seems to be a best choice. Then method was applied to free vibration analysis, and again the accuracy of results on frequencies and mode shape were excellent even at small number of terms. At last the vibration of relatively complicated case of clamped – clamped plate was analyzed and very encouraged results as to efficiency and accuracy were achieved.

Procedure of the updated calculations of disks of aero – engines with removable blades a finite element method in three – dimensional statement in the environment of Femap/Nastran

ср, 06/23/2021 - 00:00

Problematic. At adaptation of a design of discs of rotor of air gas-turbine drives (GTD) it is necessary to conduct, in particular, strength calculations for what to create the computer models corresponding to stated designs (delineations) and operation conditions. If creation of a geometrical part of model does not call special difficulties the algorithm of creation of an is finite-element grid models for carrying out of calculations of performances of the disc stress-strain conditions (SSC) with blades can be modified taking into account development of programs for calculate.

Research objective. To offer the algorithms allowing with the set exactitude to calculate performance of the SSC of discs with blades on personal computers, and also to represent outcomes in the form of schedules of type "surface".

Realization technique. On an example of the disc of 2nd stage of the compressor of GTD the algorithm of construction of a three-dimensional is finite-element grid of the disc of GTD from the separate blocks which have been "pasted together" in a unified grid has been created. Numerical calculations (a contact problem of thermoelasticity, isotropic materials) are carried out. For preparation of construction of schedules of type "surface" the interface program of transformation of the table of columns in the two-dimensional table is created.

The results of research. Are created and explicitly techniques of reaching of research objectives are described.

Conclusions. The created techniques allow to carry out on the limited computer powers exact enough control calculations of discs with blades in three-dimensional statement, to conduct visualisation of distribution of stresses and contact forces of a zone of a contact "disc-blades" in the form of schedules of type "surface".

Experience in Selection of Cavitation-Resistant Steels for Inducers of Centrifugal Pumps of JSC "VNIIAEN" Specialization

ср, 06/23/2021 - 00:00

Purpose of the study. To formulate the problems of increasing the resistance to cavitation erosion of the hydraulic parts of centrifugal pumps by selecting the most suitable steel grades and to review the experience of using cavitation-resistant steels for inducers of centrifugal pumps of JSC “VNIIAEN” specialization.

Research method. Analytical and statistical analyses were carried out using research and experimental development data of cavitation-resistant steels for inducers of centrifugal pumps at JSC "VNIIAEN", as well as using data from open access publications.

Research results. The article deals with the problem of centrifugal pump hydraulic part failure caused by cavitation. It has been actually demonstrated that the most effective way to improve the cavitation performance of centrifugal pumps is to use an inducer upstream of the first stage impeller. Therefore, the study of cavitation-resistant steels was carried out on inducers which are most exposed to cavitation when operating under condition of developed cavitation. The results of tests carried out on experimental model test rig and full-scale pumps are presented. The selection of steels resistant to cavitation has been optimized. The relationship between the chemical and mechanical properties of steels and resistance to cavitation is shown. In addition, the essential role of structural properties of steel is shown in terms of heat of steel 08Х15Н4ДМЛ.

Conclusions. The article provides a rationale for the fact that the potential for improving the cavitation-erosion properties of the hydraulic parts of centrifugal pumps solely by improving their hydrodynamic characteristics is practically exhausted; therefore, more attention should be paid to the search for cavitation-resistant steels used for the manufacture of hydraulic parts. It is shown that in order to achieve the best cavitation-erosion properties, it is necessary to provide a certain interaction of the selected chemical and mechanical properties of materials. The possibility of achieving better resistance to cavitation erosion by modifying the melting process is shown in terms of steel 08Х15Н4ДМЛ.

Key words: cavitation, pump inducer, parameters of cavitation erosion, properties of steels, castings and forgings of steel 08Х15Н4ДМЛ.

Development of a tool module for external intermittent grinding with the activation of the cutting fluid.

ср, 06/23/2021 - 00:00

Development of a tool module for external intermittent grinding with the activation of the cutting fluid.

Numerical modeling of crack initiation and propagation processes in various specimen’s types using the GTN material damage model

ср, 06/23/2021 - 00:00

Problematic. A combination of experimental and computational methods for studying the processes of crack initiation and propagation in various specimen’s types is used to determine the mechanical properties of materials, as well as to improve the accuracy of assessing the strength and durability of structural elements.

Research objective. Determination of the parameters of the Gurson-Tvergaard-Needleman (GTN) material damage model based on the numerical modeling results of various specimen’s types under various types of loading for steel 22K using the finite element method.

Realization technique. Using the finite element method, numerical modeling of the processes of cracks nucleation and propagation in cylindrical specimens under uniaxial tension, in Charpy specimens under dynamic loading, and also in CT specimens under quasi-static loading was carried out for steel 22K using the GTN material damage model.

The results of research. By comparing the experimental and numerical results, the full set of GTN material model parameters for steel 22K was determined. The stress state in the crack tip area and the kinetics of its propagation in the material of various specimen’s types under static and dynamic loading were estimated.

Conclusions. The GTN material damage model with the parameter values determined from experiments, can be used for numerical simulation of the processes of crack initiation and propagation both in specimens of various types under various loading types, and in structural elements.

Keywords: GTN material damage model, finite element method, crack initiation and propagation, Charpy specimen, CT specimen.

Modeling of cutting forces while boring heat – resistant alloy Inconel 718

ср, 06/23/2021 - 00:00

In this work, authors had made computer FEM (finite element method) simulation of machining holes in part made of heat-resistant alloy Inconel 718. For this simulation nonlinear solver LSDyna had been used. Material type for physical modeling of workpiece have been selected to JohnsonCook formulation. Tool configuration is rigid and have dynamic stiffness in three dimensions in the fastening points. Graphs of cutting forces and moments of cutting for three different depths of cut had been obtained. In the beginning of the cutting, in addition to the smooth increase of cutting forces, highfrequency oscillations with amplitudes of 13 N also take parts. The resulting cutting force has pronounced harmonic oscillations at low frequencies. The maximum burst of amplitude occurs in the period from 0.9 to 1.3 seconds from the start of cutting. It is recommended to carry out a smooth increase of cutting forces at this time through cutting modes. Highfrequency oscillations, which were insignificant in the context of each component of the cutting forces, due to the summation and oscillations of the holder play a crucial role in the oscillations of the boring moment.

Investigation of shape stability of semi-finished samples in the form of a ring made of plastic ceramic material based on SiC, obtained by injection molding

ср, 06/23/2021 - 00:00

The concept of form stability is considered. A semifinished product in the form of a ring from a thermoplastic mass based on SiC powder has been made on the installation for injection molding developed at the Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine  in accordance with the established technological parameters optimized by the results of computer modeling. Schemes of loading and dividing the ring into samples in the form of prismatic segments are presented. A technique for the preparation of experimental samples is proposed. The study of the compressive strength of the samples from the injected semi-finished product has been carried out on the FP-5 mechanical test machine and a corresponding здще of its change has been constructed. The formation of a barrel shape during compression tests of samples, both along the radial and tangential directions, has been established. The values of the minimum and maximum loads at which the samples are destroyed have been determined. An increase in the compaction of the thermoplastic mass around the injection point has been experimentally proved. The scheme and the actual image of crack distribution as a result of destruction of samples have been presented. It is shown that the failure occurs in the area of the presence of the calculated parting lines, which have become stress concentrators.