Technological processes and material science. Рубрика в журнале - Siberian Aerospace Journal
Interaction of magnetic and dielectric subsystes in a bismuth nodymic ferrite-granate
Scientific article
Bismuth-substituted ferrite garnets possess magneto-optical (MO) properties and are used as spatial light modulators and indicators. The paper studies the influence of magnetic and electric fields on the structural characteristics of thin epitaxial films of bismuth-neodymium ferrite garnet (Bi: NIG) deposited on glass and gallium gadolinium garnet (GGG) substrates. Dynamic properties of polarization, relaxation in a magnetic and electric field are considered, which is an important task for getting a deep insight into the mechanisms of electromagnetic phenomena in solids. Dependence of the magnetostriction coefficient on the magnetic field and dependence of a relative change in the length of the film on the electric field at different temperatures are obtained. A change in the sign of magnetostriction constants with respect to temperature was found. The electric polarization in a periodically applied electric field of 400 V / cm with a frequency of 10 MHz is determined for various magnetic field orientations of 12 kOe and in the absence of a magnetic field. Anisotropy of polarization in a magnetic field and a functional dependence of the polarization relaxation on time are found. These materials can be used as sensors of the magnetic field in a spacecraft.
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Scientific article
The relevance of the work is explained by the significant problems of the modern aerospace industry, mechanical engineering, energy, mining, processing and other industries in the disposal of waste products made of composite materials and products based on composites of various functional purposes (carbon fiber, fiberglass, metalceramic and cast glass reinforced). The aim of the work is to increase the efficiency of processes for obtaining micron fractions of composite materials waste through the use of an upgraded roller crushershredder design. Computational and experimental studies have substantiated the possibility of increasing the efficiency of waste recycling of composite materials due to their gradual (step-by-step) disintegration. Based on analytical calculations and finite element analysis methods, a kinematic scheme, layout and design of an up-graded prefabricated roller crusher-shredder with working bodies (discs) in the form of an equiaxed contour – a Relo triangle – have been developed. The new design implements a more complex system of forces (compression, friction, alternating cyclic loads) compared to analogues, which makes it possible to increase the speed and productivity of the crushing process. The process of cutting the material using the “rotating scissors” mechanism is implemented between adjacent counter knives of the PK profile, which also contributes to more intensive grinding of the material (especially when processing lamellar or long fragments of waste). The original location and inconsistency of the contact points of the oncoming profiles, the gap between the discs during their rotation creates a rolling effect due to the reciprocating movement of the crushed material, which reduces the risk of jamming and increases the throughput of the grinding rolls and the intensity of the disintegration processes. In order to determine the best performance in terms of the size of the working bodies of the crusher, the gap between them when grinding materials with different sizes and properties, kinematic models were created to simulate the grinding processes and conduct a numerical experiment using finite element analysis methods. It is shown that due to the effective combina-tion of various fracture mechanisms (abrasion, crushing, cutting, alternating loads), the intensity of deformation processes and specific loads on the material increases, but the stresses on the working surfaces of the crusher vary in the range of 430–580 MPa, the safety margin of the working bodies increases to 0.43–0.65, which is a prerequisite for increasing the service life of the workers. grinding elements. The results of calculations using new methods and kinematic schemes show that the design of the upgraded prefabricated roller crusher with working bodies in the form of a Relo triangle has an increased resultant speed (by 30 %) and productivity is almost 2 times higher than the prototype with cylindrical rolls (with the same or comparable sizes of working bodies, kinematic parameters in terms of rotation speed and drive power). Design and technological preparation were carried out and a prototype of the installation for experimental studies was made, which confirmed a good agreement between the calculated and experimental data on the size of the gap, the speed and productivity of the crushing and crushing process.
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Laboratory separator of bulk materials
Scientific article
New materials for spacecraft radiation screens engineering require a fine classification of powder materials by particle size. The article concerns the construction of powder materials laboratory separator. This type of material separation is related to gravity methods. The Moseley laboratory separator serves as the prototype of the construction with table longitudinal shaking and diametrical vibrations by means of buffers during the separation process. The unbalanced oscillator yields deck separation surface harmonic vibrations in all directions. The unbalanced oscillator DC motor voltage control gradually alters the vibration frequency and supports finer separation of the material. A power pipe enables to conduct perpetual separation process. In prototype, in contrast, up to 100 g weight is processed for up to 5 minutes. To improve the materials fine and small classes separation efficiency, riffles are made on the separation surface, which determine the places of concentration of material particles. As a result of the conducted researches for elimination of the secondary circulation flows, a system of diametrical reefing is worked out: the riffle is approximately equal to the maximum particle size of the separated material and is equal to 0.2 mm in this construction; the distance between riffles is equal to 50 mm, the tilt angle is 80 degrees relative to the deck longitudinal side. The particle motion depends on the inclination angle of the separation surface. Large particles move upwards at angles of up to 5 degrees, and downwards at angles higher than 5 degrees. Vibration frequency and amplitude alteration, as well as adjusting the inclination angle of separation surface enables to move and adjust the speed of different properties and sizes of test material. The laboratory separator work is based on the physical effects, which enable to vary the location of the power pipe. This fact allows the construction to be adapted to a variety of specific conditions and expands the construction sphere. The separator construction is simple for production and operation, and can be quickly reconfigured if necessary. The separator portability allows it to be transported.
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Laser processing of titanium alloys to increase the strength of adhesive joint with cfrp
Scientific article
Titanium alloys are hard-to-bond materials due to the fact that a thin oxide film is always present on their surface, which prevents the formation of interatomic and intermolecular bonds between the adhesive and the substrate. In the load-bearing structures of spacecraft (SC), an adhesive bond between a titanium alloy and a composite material is often used. But the strength of such knots is relatively small compared to the mechanical connection. The purpose of this work is to increase the strength of the adhesive joint, due to laser processing of the working surface of the titanium alloy for gluing. Texturing of the surface of the tita-nium alloy OT-4 was carried out on an ytterbium pulsed fiber laser in 4 processing modes. The treated sur-face was glued with KMU-4 carbon fiber over an area of 300 mm2 using a VK-9 three-component adhesive. The adhesive strength test was carried out on a Eurotest T-50 tensile tester. The test showed that the strength of the laser-treated samples increased by more than 80% relative to the average value of mechan-ical grinding. The highest value of shear strength was shown by samples with laser processing No. 1 and No. 3. This is due to the greatest increase in the area of bonding of the surface, as well as the mechanical locking of the adhesive in the microrelief of the structure. The increase in shear strength caused by laser surface treatment is a mixed effect of increasing surface area, mechanically locking the adhesive, and changing the surface chemistry. The chemical composition of the surface structure under the influence of laser scanning is gradually transformed from Ti and Ti2O3 to crystalline TiO2. The nature of the destruc-tion of the adhesive joint in the samples with laser processing is predominantly cohesive, but samples with the destruction of the carbon fiber material were also observed, that is, the shear stress in the composite material exceeded the adhesive strength. The effect of pretreatment of the composite material on the strength of the adhesive joint was not considered in this work.
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Magnetic capacity in manganese sulfides with rare earth substitution Mn1-xRexS
Scientific article
Polycrystalline samples Mn1–xGdxS and Mn1–xYbxS with a concentration x = 0.2, near the concentration of ion flow through the fcc lattice, are studied in order to determine fluctuations in the valence of the ytterbium ion on dielectric properties. Dielectric constant and dielectric losses were determined from measurements of capacitance and loss tangent in the frequency range 102–106 Hz at temperatures of 80– 500 K without a magnetic field and in a magnetic field. The magnetic capacity and dielectric losses in the magnetic field of the sample were determined from the relative change in the real and imaginary parts of the dielectric constant of the sample in a magnetic field H = 12 kOe applied parallel to the capacitor plates. A temperature range with a sharp increase in dielectric constant and with a maximum dielectric loss has been discovered, which shifts with increasing frequency and magnetic field. An increase in dielectric constant and dielectric losses in a magnetic field above 170 K was found in Mn1-xYbxS. The increase in dielectric losses is explained by an increase in relaxation time, as a result of local deformations near ytterbium ions during valence fluctuations. The mechanism for reducing reactance in a magnetic field in Mn1–xYbxS at low frequencies due to capacitance, and at high frequencies due to inductance, has been determined. In the Mn0.8Gd0.2S compound, the imaginary part of the dielectric constant has two maxima. The low-temperature maximum shifts in a magnetic field towards high temperatures and is described in the model of localized electrons with freezing of dipole moments. Dielectric losses decrease in a magnetic field. The magnetic capacity decreases by an order of magnitude in Mn0.8Gd0.2S compared to Mn0.8Yb0.2S. The dielectric constant in both compounds is described in the Debye model with the activation dependence of the relaxation time on temperature, where the activation energies differ for ytterbium and gadolinium ions.
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Magnetic characteristics of iron nanoclusters
Scientific article
The study of the nanocrystalline state, which significantly changes most of the physical characteristics of sub-stances, is very relevant. Of great practical interest are the works devoted to the study of the magnetic character-istics of nanocrystals of ferromagnetic substances. It has already been shown that the size of iron nanocrystals significantly affects the magnitude of their magnetization. Nevertheless, an adequate model of the structure of nanocrystalline formations consisting of a different number of iron atoms, which allows us to describe the exper-imentally detected changes in the magnetic characteristics, has not yet been presented. In this paper, we analyze nanocrystalline iron clusters that are different in configuration and number of their constituent atoms. Spatial models of clusters are constructed using a three-dimensional modeling program, and the coordinates of individual atoms in the cluster are determined. The proposed structures of nanocrystals are based on tetrahedrally close-packed cluster assemblies of iron atoms. The electron state density spectra were con-structed for the proposed clusters. For this purpose, the theory of the electron density functional was used, the calculation was carried out by the method of scattered waves in accordance with the band theory of crystals. It is shown that the appearance of magnetization in tetrahedral densely packed cluster formations is associat-ed with the excited electronic states of the atoms located on the surface of the nanocluster. Excited atoms have an increased electron density, that is, electrons are able to transition to states with higher energy, approaching the Fermi energy. In this case, the Stoner criterion necessary for the occurrence of magnetization is fulfilled. The con-figurations of electrons with spin up and down differ, which is why uncompensated magnetic moments appear. It is confirmed that the proposed models of iron nanoclusters satisfactorily correspond to the known experimental data.
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Magnetic impedance in nonstichiometric manganese sulfide
Scientific article
The role of defects on the dynamic characteristics of manganese sulfide is studied by impedance spectroscopy in the frequency range 102–106 Hz and temperatures 80–500 K. Nonstoichiometry plays an important role in the formation of new transport and magnetic properties, as it leads to electrically inhomogeneous states. The phase composition and crystal structure of nonstoichiometric manganese sulfide were studied on a DRON-3 X-ray unit using CuKα – radiation at room temperature. According to X-ray diffraction analysis, the synthesized compound is single-phase and has a NaCl-type cubic lattice. From the frequency dependences of the impedance components measured in the absence of a field and in a magnetic field, the relaxation time of the current carriers in the Debye model is found. A sharp decrease in the relaxation time and its correlation with conductivity were found. The contribution to the impedance of the active and reactive parts of the impedance at frequencies below and above the relaxation time is established. The capacitance from the impedance hodograph in the equivalent circuit model is determined. In defective manganese sulfide, the temperature-dependent impedance has an activation character. The activation energy is determined in the range 250–500 K, which is attributed to the excitation energy of lattice polarons. The effect of a magnetic field on the dynamic characteristics of current carriers was studied as a result of a change in the impedance components in a magnetic field at fixed temperatures. The impedance increases in a magnetic field and reaches a maximum in the temperature range of charge ordering of vacancies. An increase in the impedance in a magnetic field is explained by a decrease in the diagonal component of the permittivity in a magnetic field in an electrically inhomogeneous medium. The experimental data are explained in the Debye model.
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Scientific article
Bismuth pyrostannate Bi2Sn2O7 is a diamagnet and belongs to the structural type of the A2B2O7 pyro-chlore class. In this class of compounds, in the presence of magnetic ions, very interesting magnetic proper-ties appear. Chromium- and iron-substituted bismuth pyrostannates Bi2(Sn0.9Me0.1)2O7, Me = Cr, and Fe were synthesized by solid-phase synthesis. X-ray diffraction analysis showed that the samples correspond to the Pc monoclinic cell of the Bi2Sn2O7 α-phase at room temperature. The magnetic properties up to 1100 K in magnetic fields up to 0.86 T and the electric polarization at frequencies of 10, 3, and 1 mHz in the tem-perature range 80–550 K have been studied. The effect of heterogeneous substitution by Cr3+ and Fe3+ ions on the magnetic properties and electric polarization of bismuth pyrostannate is investigated. An analysis of the experimental data revealed the dependence of the magnetic properties on the degree of filling of the elec-tron shells of chromium and iron ions. The Bi2(Sn0.9Cr0.1)2O7 compound exhibits ferromagnetic properties, while Bi2(Sn0.9Fe0.1)2O7 exhibits antiferromagnetic properties. In chromium-substituted bismuth pyrostan-nate during the α→β transition, the paramagnetic Curie temperature increases by a factor of 3. The temper-ature dependence of the inverse magnetic susceptibility is characterized by hysteresis in the temperature range of 400–900 K. The reverse magnetic susceptibility of Bi2(Sn0.9Fe0.1)2O7 in the entire temperature range is satisfactorily described by the Curie-Weiss law. Studies of the magnetic properties have established that the Fe3+ ions are in a high-spin state. The polarization hysteresis in Bi2(Sn0.9Cr0.1)2O7 is found, which shifts along the polarization axis and depends on temperature. Bi2(Sn1-xFex)2O7, x=0.1 is characterized by a linear field dependence. With an increase in the concentration of iron ions, a hysteresis arises in the field dependence of the electric polarization. The hysteresis of polarization in Bi2(Sn0.9Cr0.1)2O7 which depends on temperature was found. The nonlinear field dependence of the polarization in Bi2(Sn0.8Fe0.2)2O7 can be ex-plained by the interaction of the dipole and migration polarizations and the presence of oxygen vacancies. For the Bi2(Sn0.9Cr0.1)2O7 compound, a transition to the dipole glass state was found. In the β-phase of Bi2(Sn0.8Fe0.2)2O7 above T = 400 K, no polarization hysteresis is observed and the electron-relaxation polar-ization predominates. The mechanism of the occurrence of electronic polarization is explained with the ap-pearance of anionic vacancies upon heterogeneous substitution of tin ions.
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Magnetic properties of Mn1-xGdxSe sol-id solutions
Scientific article
Potential materials for spintronics operating under extreme conditions based on manganese selenides substituted with gadolinium are investigated. The technology of synthesis of solid solutions based on solid-phase reactions using MnSe and GdSe compounds is presented. As a result, Mn1-xGdxSe solid solutions with concentrations x = 0.05; 0.1; 0.15 and 0.5 were synthesized. The synthesis was carried out under vac-uum conditions of 10–2 Pa. The products of the primary synthesis were subjected to thorough grinding into powders, from which tablets were made under pressure for homogenizing annealing at 1370 K. After two hours of exposure, the synthesis products were tempered in cold water. At the final stage, homogeneous strong ingots of greyish-silver color were obtained. X-ray phase analysis of synthesized solid solutions of the Mn1-xGdxSe system was performed in Cu-K radiation in the point-by-point measurement mode with a scanning step along the angle Δ2θ = 0,03 degree; the time of information collection at the reference point Δτ =3 seconds. The spatial symmetry group and the parameter of the elementary crystal cell of solid solu-tions of the Mn1–xGdxSe system from X-ray diffraction analysis are determined. The dependence of the pa-rameter value of the crystal lattice of solid solutions on the concentration of gadolinium ions is found. The specific magnetization was measured by the ponderomotor method in a magnetic field with an induction of B = 0.86 Tesla and the magnetic susceptibility of the samples was determined in the temperature range of 80 ≤ T ≤ 950 K. The cycles carried out in the heating - cooling mode did not detect a change in properties. The Neel temperatures and the paramagnetic Curie temperature are determined from the Curie – Weiss law depending on the concentration of a rare earth element. A decrease in the temperature of the magnetic phase transition is established.
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Magnetoimpedance in thulium manganese chalcogenide
Scientific article
Control of transport characteristics under the influence of a magnetic field is promising from the point of view of creating magnetic field sensors resistant to radiation. The impedance and its components in thulium manganese chalcogenide in the frequency range of 102–106 Hz are studied. The temperature range with a prevailing contribution of the reactive and active parts of the impedance is found. The impedance components are described in the Debye model. When manganese is replaced by thulium ions, the frequencies of the maxima of the imaginary component of the impedance shift toward high frequencies in manganese selenide by two orders of magnitude. With an increase in the concentration of substitution by thulium ions in selenides, two relaxation times are found, compared with sulfides. The activation nature of the relaxation time, the activation energy from the concentration of thulium ions are found. An increase in impedance in a magnetic field in the region of low concentrations and a change in the sign of the impedance with temperature for high concentrations are established. Magnetoimpedance in chalcogenides passes through a maximum when heating the samples. The increase in impedance in a magnetic field is due to a change in the diagonal component of the permittivity in a magnetic field, which is proportional to the conductivity. A positive value of magnetoimpedance is described in the model of an electrically inhomogeneous medium. From the impedance, information can be obtained about the electrical inhomogeneity of the material.
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Scientific article
Operational characteristics of contacting elements of cars and mechanisms are by far defined by a layer quality indicators at the surfaces of contact. One of the ways of increasing details durability, including missile and space equipment details, is the superficial plastic deformation (SPD). In the article aspects of dynamic ways of hardening from the position of the wave theory of blow are considered. The construction of a shock stand on the basis of a linear electrodynamic drive with a size of 60 mm, operating in a shock-pulse mode, as well as a well-known mathematical model of the workflow – the movement of the armature with the tool at the moment of striking the surface. This model does not fully describe the operation process since the mass of the striker taken into account equaled 1 kg, which does not characterize the process of the impact tool, the purpose of which is the object deformation (for example, work hardening with the aim of surface material sealing or breakdown of the hole in it, or applying license plates markers). The mathematical model that describes the movement of the armature with the tool, taking into account the elastic deformation of the hardened surface was obtained. In the course of the performed calculation, the magnitude of the elastic deformation of the hardened surface was calculated from the dynamic component of the force impulse applied to it through the indenter (the tip of the impact tool). The layout of the shock stand with the equipment used, are offered. Experiments on the signal recording with various arrangements of piezoelectric transducers on the anvil – the hardened surface (diagrams of the sensors location are given) were carried out.
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Mathematical modeling of the flat ingot casting process for solving automation problems
Scientific article
Aluminum alloys are widely used in the production of aircraft due to their strength, lightness, corrosion resistance, and necessary electrical conductivity. At the same time, aluminum ingots used in further processing of the space industry must be of high quality. Technological problems and defects arise when temperature, speed, and other technological parameters of casting are not observed, or when modes change. At the same time, foundry processes are partially automated; the human factor significantly affects product quality and work safety. Therefore, automation of these complex processes using mathematical models to predict casting parameters is an urgent task. The goal of the work is to create mathematical models available for use in automated process control systems (APCS), as well as for the development of a digital twin. The work presents simplified formulas for modeling the temperature distribution of an aluminum ingot during the casting process, cooling the metal when moving along a metal path, and test calculations of the temperature distribution inside the ingot when the ingot reaches a fixed length. The results of this work can be used to improve the efficiency and accuracy of controlling the process of casting aluminum ingots, to eliminate emergency situations.
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Scientific article
In this scientific work, a method of controlling high-frequency products from polymeric composite materials is considered. The authors of the work present the rationale for choosing a method of high-frequency diagnostics as the most suitable for non-destructive testing of products from polymeric materials of machine-building and rocket-space purposes. In the presented article, the primary task of creating and studying a mathematical model of the effect of highfrequency radiation on a polymer product, including those with a “metallic inclusion” defect, has been stated and solved. In addition, the work presents the calculations of diagnostic parameters using the mathematical model developed during the study. The calculation of the dynamics of heating the product and the temperature distribution during the control process is presented. The results of the calculation of specific power are described, the dependence of the instantaneous power consumption on the warm-up time is found. In the study based on a mathematical model, the Aleo- Diagnost software package was developed and registered, which is directly intended to ensure the functioning of the diagnostic devices and the investigation of the monitoring process. In addition, the developed complex allows solving a number of such practical problems as the calculation of the operating voltage depending on the geometrical parameters of the product and the determination of the value of energy consumed for monitoring the product for a specified period of time. This stage was necessary, as the consumed energy is the main output parameter of the diagnosis. In addition, the value of energy consumed is taken as the basis for the organization of the process of non-destructive testing in the automated mode. The solution of the tasks in this work has significantly reduced the cost of preparation of diagnostic operations, as well as improve the quality of control of products on an industrial scale at the stages of manufacture, operation and during repair work. The article also presents practical results, conclusions.
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Scientific article
The article contains the results of scientific research on modeling the technological parameters of electron beam welding. The modeling used a material VT-14 with a thickness of 0.16 cm. The purpose of the simulation is to improve the quality of the weld due to the optimal shape and the absence of defects in the form of pores and cracks. A concentrated energy source equivalent to an electron beam is used in the calculations. During the study of the thermal process of heating the material, the authors developed and tested criteria that allow optimizing welding parameters such as welding speed and the position of the focal spot relative to the surface of the heated part. In their calculations, the authors applied an original method of finding the welding speed and the coordinates of the focal spot according to the functionals of the thermal model. The algorithm developed by the authors was successfully tested on AMG-6 material with a thickness of 10 cm. In the process of modeling welding for large thicknesses, results have been obtained that must be taken into account when optimizing the welding parameters of products with large thickness. The relevance of the presented material is confirmed by the demand for the quality of the technology of welding structures with an electron beam. Research by the authors of this direction will significantly expand the possibilities in the application of electron beam technology for rocket and space technology.
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Numerical analysis of the influence of defects a on the durability of turbomachines working blades
Scientific article
The aim of the study is to numerically analyze the effect of damages and defects of various types and levels on the fatigue life of blades and impellers of axial and radial turbomachines. In the field of turbine technology, it is of particular importance to increase the durability and reliability of turbine blades, especially in conditions of defects and parameter adjustments. Defects such as cracks, corrosion, material irregularities, etc., can significantly reduce the service life of components, causing the risk of accidents and increasing operating costs. The article presents a numerical analysis of the effect of parameter adjustments related to turbine blade defects on their durability. The research includes the development of mathematical models based on the finite element method (FEM) to assess the impact of damage on the strength characteristics of the working blades of pipe machines. The research methodology is based on the use of FEM using modern software systems, as well as machine learning algorithms. The analysis results showed that impeller fatigue life varies significantly depending on the location and orientation of cracks and damage. These findings can be used to develop diagnostic and service life prediction methods for turbomachines, as well as to optimize their design to improve operational reliability. The study demonstrates the possibility of increasing the durability of the blades by purposefully changing their geometric parameters.
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Scientific article
The results of the study of the damping capacity of manganese-copper alloys based on the Mn – 40 % Cu alloy with additives (0.5 – 1.5) % zirconium in the field of amplitude-independent damping are present-ed. Mn – Cu alloys with high damping capacity can be effectively used to reduce vibration and noise. Stud-ies on the influence of a number of alloying elements on the magnitude and stability of the damping capaci-ty of Mn – Cu double alloys in the field of small deformations of relative shear are not enough. In the pa-per, the influence of one of these elements, zirconium, was elucidated. Mn – Cu alloys were smelted in an induction furnace. From the ingots cast into cast iron molds, samples for studies with dimensions (11 × 15 × 117) ± 1 mm were obtained by mechanical cutting. The samples were subjected to aging at a temperature of 643 K for 0.5–40 hours. The damping capacity of Mn – Cu alloys (the logarithmic decrement of attenua-tion of oscillations) was studied for longitudinal oscillations of samples in the frequency range 14–17 kHz and the amplitudes of the relative shift (1 ... 3) × 10–6. It has been established that alloying the Mn – 40 % Cu alloy with zirconium from 0.5 % to 1.5 % does not increase its damping capacity in the cast state, as well as in the cast and aged at a temperature of 643 K for 40 hours. It was found that the minimum values of the frequencies of resonant vibrations of samples of Mn – Cu alloys correspond to the maximum levels of the damping capacity of these alloys. Itʼs shown that the high damping capacity of cast and aged alloys at 643 K for 40 hours Mn – 40 % Cu, Mn – 38.5–39.5 % Cu – 0.5–1.5 % Zr after natural aging at 293 K for 7 months decreases by 2.0–2.6 times.
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Scientific article
The analyzes of the requirements to 3D-configuration pipelines production at the rocket and space industry enterprises is done. A review of different approaches to pipe bending technology (with heat treatment and without heat treatment) is carried out. The object of the study is the bending process and a universal bending machine for pipelines’ production of complex configuration. The article is divided into four sections, which consider the key factors, causing directly the effectiveness of the technological operation of pipeline bending of a complex 3D-trajectory. An overview of no-temperature shaping of the pipeline is given in the first section. The requirements to the technology, excluding: corrugation, flattening, stretching and thinning of pipeline walls during their bending, are considered. The actual regulatory documents and industry aerospace standards, regulating production of pneumatic and hydraulic pipelines are given. An example of calculating the minimal allowable bend radius of the pipe, depending on the diameter and thickness of the pipe wall, is given. The requirements to unification of the pipe size production and gaps are listed. The dependence of the maximal allowable internal pressure in the pipeline is shown. The requirements to equipment, used in pipeline bending and to the design of the pipe bending machine are considered. In the second section, the possibilities of temperature influence on the pipe bending process are viewed. The analysis of patent and technical literature and six possible methods of effective thermal effects are presented: heating of the whole pipeline length, narrow zone heating of the bend pipe place, water cooling with nitrogen in the pipe, laser-cooling of atoms of the pipes, application of the petroleum products on the place of heating of the pipe and using of modern fillers inside the pipe to change its temperature. In the third section the tasks of the development of a universal bending machine are set; the system of the algorithm of the universal bending machine operation is considered; the system of algorithm of the bending machine operating with CNC is shown. The General functional scheme of the bending machine and the sequence diagram of the equipment operation is given.
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Plasma spheroidization of metal and ceramic powders
Scientific article
The paper presents the results of plasma spheroidization of metal and ceramic powders. The aim of the study was to conduct a comparative analysis of two methods for feeding powders into a plasma jet – under the nozzle section (plasma torch F-4) and along the axis of the plasma jet (plasma torch PM-1). Metallic (Cu, NiCr) and ceramic (Al2O3, ZrO2) powders were used as objects of research. To implement the spheroidization process, a specialized water-cooled reactor has been developed that provides controlled cooling of molten particles. Numerical modeling of thermal processes in the reactor confirmed the efficiency of the cooling system: the stationary thermal regime is established 286 seconds after the start of operation of the plasma torch, and the increase in the temperature of water in the reactor, measured experimentally, is consistent with the data obtained by calculation and is 5 °C. It has been established that the PM-1 plasma torch provides homogeneous and finely dispersed powders, however, when processing materials with a low melting point (copper), the powder begins to melt in the inlet channel of the plasma torch, settles on the walls of the nozzle and, over time, clogs it. Spheroidization with the supply of powder under the nozzle section makes it possible to process any materials, however, larger particles with a wide granulometric distribution are formed, especially when processing refractory powders. Based on a comprehensive analysis of the microstructure and granulometric composition of spheroidized powders, technological recommendations have been formulated for choosing the type of plasma torch depending on the required powder properties: the PM-1 plasma torch is preferred for obtaining homogeneous fine powders, and the F-4 plasma torch is preferred for processing low-melting materials and ensuring the maximum degree of spheroidization.
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Plasmotron for coating internal surfaces of component parts
Scientific article
Plasma spraying is one of technologically appropriate, productive and effective methods of applying protec-tive coatings to component parts produced by aerospace, metallurgical and other industries, objects exposed to high temperatures, dynamic loads, aggressive media, etc. Plasma spraying makes it possible to apply quite a va-riety of materials, such as metals, oxides, carbides, nitrides, etc. to different surfaces. Certain problems may arise, though, in applying protective coatings to the inner surfaces of cylinders and complex parts of small size (about 100 mm). These complexities depend on the dimensions of the plasma generator proper. There are no home-produced small-size plasma torches, they are all imported from other countries. That causes certain prob-lems with delivery, to say nothing of very high commercial price. One of the ways to improve the situation is to develop small-size plasmatrons capable of applying high-quality coatings to the internal surfaces of limited-size parts; that may significantly reduce expenses through import substitution. The effectiveness of the proposed device is in working out a method of applying high-quality coatings to the inner surfaces of orifices as small as 60 mm in diameter (operating a plasmatron of smaller size), as well as in significant cost reduction due to domestic production. Sample calculations show that the price of that plasma-tron type will not exceed 0.5 million rubles.
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Point defects in nematic liquid crystal materials with conical anchoring at the interface
Scientific article
The topological point defects in nematic liquid crystal materials have been studied. The method of oblique light incidence has been proposed to determine an azimuthal director angle of an achiral nematic as well as a chiral nematic (cholesteric). The idea of the method is based on the dependence of the optical phase difference between ordinary and extraordinary light beams on the azimuthal director angle at the layer center at oblique incidence of light on a structure in which the polar director angle of a nematic liquid crystal is not equal to 0° or 90° (conical boundary conditions). It has been shown that the phase difference reaches a maximum at a zero azimuthal angle at the center of the layer regardless of the total twist angle of the director. The developed method has been used to analyze topological defects formed in the nematic and cholesteric layers under conical boundary conditions at the interface. The director field distributions of nematic and cholesteric near the surface point defects (boojums) with topological charges m = +1 and m = –1 have been drawn based on the experimental data. The proposed method of oblique light incidence can be used to analyze a wide class of the achiral and chiral liquid crystal media of various types: smectics, nematics, and cholesterics with tilted or hybrid boundary conditions.
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