Technological processes and material science. Рубрика в журнале - Siberian Aerospace Journal
Статья научная
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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Статья научная
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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Plasmotron for coating internal surfaces of component parts
Статья научная
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
Статья научная
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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Prediction of formation of competing phases during the growth of Cr2GaC THIN FILMS ON MgO(111)
Статья научная
MAX-phases are a family of ternary layered compounds with the formal stoichiometry Mn+1AXn (n = 1, 2, 3...), where M is a transition d-metal; A is a p-element (for example, Si, Ge, Al, S, Sn, etc.); X is carbon or nitrogen [1]. Layered triple carbides and nitrides of d-and p-elements (MAX-phases) exhibit a unique combination of properties characteristic of both metals and ceramics, which makes their application as various coatings in space industry very promising. Obtaining the desired properties of the MAX-phases depends on the technological conditions of material synthesis. This requires thorough theoretical modelling of the elements’ interaction at the interface. Concurrent growth of competing phases along with the MAX-phase may occur due to the favorability of competing phases’ formation and may also be promoted by lower energy interfaces with the substrate in comparison with a MAX-phase. In this work, we study thermodynamic favorability of competing phases and Cr2GaC MAX-phase depending on the chemical composition of the atomic flow. To study these compounds, it was necessary to consider the Cr-Ga-C system. According to the effective heat of formation model, each reaction of a certain phase formation can be characterized by enthalpy [2]. To find out the most favorable phases, it was necessary to calculate the enthalpy of all possible reactions. Thus, the task was to sort through all possible reactions between pure elements available in various ratios, in particular, in the ratio corresponding to the given MAX-phase stoichiometry, i.e. Cr:Ga:C=2:1: 1. Moreover, it is considered that the density of near-coincidence sites [3,4] for interfaces between MAX-phase, thermodynamically favourable competing phases and MgO(111) surface shows a role of the interface in the determination of the structural quality of the MAX-phase thin film grown on MgO(111).
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Production of finly despersed powder from graphite by electrolysis
Статья научная
Multifunctional coating is a multi-layer structure applied to the surface of an aircraft to protect it from external influences. The main tasks of the multifunctional coating are: restoration of properties, overall dimensions, mass of the surface of the product, which were violated under operating conditions; changing the initial physical, mechanical and chemical properties of the product surface to ensure the specified operating conditions. Today multifunctional coatings based on micro glass spheres with applied tungsten are widely used in aerospace engineering. However, this coating has a number of disadvantages: the coating layers heterogeneity; the composition contains a harmful and dangerous component – a fluorone dye. In this article it is suggested to replace the main component of a multifunctional coating with finely dispersed graphite powder obtained by electrolysis. For this purpose, the equipment based on the principle of a diaphragm electrolyzer was constructed. The main elements of the device are a stainless steel cathode and a graphite anode immersed in an aqueous solution. As a result of anodic processes, a finely dispersed graphite powder was obtained. The average particle size of the resulting graphite particles is 4 microns. This finely dispersed graphite powder can be used as the main component of a multifunctional coating in aircraft, since it has an even homogeneous structure, as well as higher values of the main mechanical properties of a multifunctional coating.
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Статья научная
The paper presents the results of studying the shielding properties of thin transparent films in single-walled carbon nanotubes on flexible substrates of polyethylene terephthalate. The films were formed by spraying colloidal solution on single-walled carbon nanotubes. The film thickness was determined by the volume of the sprayed colloidal solution and was measured using transmission electron microscopy in a cross-section mode. The morphology and structural quality of the films were studied by electron microscopy, optical spectroscopy, and Raman spectroscopy. The results showed the high structural quality of the material. According to Raman spectroscopy, the ratio of peaks intensities G / D is 23.4, which is the evidence of a significant predominance of carbon in the sp2 hybridization. It is typical for graphitelike systems and, in particular, carbon nanotubes. The spectral dependences of the transmission and reflection coefficients of radio waves in the K range of 18–26.5 GHz were studied. Absorption of radiation is the dominant shielding mechanism. Increasing the film thickness from 15.9 to 56.1 nm is accompanied by decreasing the surface resistance from 971 to 226 Ohm / sq, while optical transparency decreases from 93.58 to 76.71 %. Shielding efficiency increases from 2.29 to 6.6 dB, increasing the proportion of absorbed radiation from 34.6 to 51.2 % at a frequency of 18 GHz. This indicates the prospects for the use of films as electromagnetic shielding and anti-icing coatings in the aerospace industry.
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Research on electrical properties of manganese sulphides doped by thulium and ytterbium ions
Статья научная
Materials exhibiting connection between electrical and magnetic properties are attractive for possible use as an element base in microelectronics, spintronics, and sensor devices. Compounds with mixed valence exhibit a number of metal-insulator phase transitions, magnetic phase transitions, including changes in magnetic properties without changing magnetic symmetry. Promising materials for studying these effects are cation-substituted Mn1−xRexS compounds (Re = 4f elements) synthesized on the basis of the antiferromagnetic semiconductor of manganese monosulfide. The latter is of practical importance in the development of new materials for temperature sensors, widely used in the metallurgical industry. The structural and electrical properties of compounds with mixed valences TmXMn1-ХS (0 ≤ X ≤ 0.15) and TmXMn1-ХS (0 ≤ X ≤ 0.25) were studied in the temperature range 80–1100K. The regions of existence of solid solutions of TmXMn1-XS sulfides with an fcc (face-centered cubic) lattice of the NaCl type were determined. It was found that conductivity decreases upon the substitution of manganese cations with thulium ions and the lattice constant increases more sharply in comparison with Vegard’s law. When ytterbium ions are substituted, the conductivity increases with increasing concentration and the temperature dependence has the form typical of semiconductors.
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Simulation of the induction soldering process of waveguide paths from aluminum alloys
Статья научная
A system of waveguide paths is a complex structure of various elements with various geometries. Induction soldering based on the induction heating method is one of the promising methods for waveguides fabricating. Induction soldering of waveguide paths has a number of technological features: the melting temperature of the base material AD31 (695–663 0C) slightly differs from the melting temperature of St. AK12 solder (577–580 0C) at an average induction heating rate of 20–25 0C / sec; a wide variety of standard sizes of waveguide paths elements complicates the development and subsequent reproduction of technological parameters of the induction soldering process; zones of maximum heating of waveguide paths elements do not coincide with zones of soldering. Therefore, to solve the problems of controlling the waveguides soldering process, it is necessary to simulate this process. The paper deals with the problem of simulating the process of heating a waveguide during induction soldering. Requirements for the process model have been formed. The model is built on the basis of the differential heat conduction equation. The formed model requirements take into account the geometric parameters of waveguides, the physical parameters of materials, the initial and boundary conditions, as well as the uneven distribution of eddy current density in the waveguide. It is proposed to use the finite difference method for the numerical solution of the heat conduction equation. The process of calculating the temperature at the grid nodes is shown. The authors propose a two-stage solution. At the first stage, at an intermediate time step, the temperature at the grid nodes along the X axis is calculated. At the second stage, the temperature at the grid nodes along the Y axis is calculated. The numerical solution of the difference equations along the X and Y axes is carried out by the sweep method. An algorithm for the numerical solution of the heat conduction equation has been developed.
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Spraying plasmatron coatings with powder supply to plasma flow
Статья научная
The efficiency of using plasma energy when applying coatings is largely determined by the design of a plasma-tron. The main difference of the developed plasmatron PM-1 is the supply of transporting gas with powder to the plaza flow, which allows us to ensure more efficient and uniform heating of the material being sprayed. This paper presents the results of measuring a material usage factor (MUF), which is an important and indicative characteristic of plasmatrons, showing their economy and productivity. The authors calculated the cost of electricity and con-ducted studies of the sprayed samples for thermal shock.
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Structural-phase state and properties of hypereutectic silumin treated with a pulsed electron beam
Статья научная
Hypereutectic silumin composition are promising modern materials of wide application (mechanical engineering, aviation, instrumentation, medicine, etc.). Disadvantages of hypereutectic silumin, significantly limiting their scope of application, are pores and cavities, large (about 100 µm) inclusions of lamellar and needle-shaped second phases. As a result of the studies carried out in this work, the possibility of forming structural-phase states in the surface layer of silumin, the size and morphology of which can purposefully change in the range from tens of micrometers to tens of nanometers, is demonstrated. The irradiation modes that allow more than 5 times to increase the microhardness (15 J/cm2, 150 µs, 0.3 s–1, 5 imp.) and more than 3 times to increase the wear resistance (50 J/cm2, 150 µs, 0.3 s–1, 5 imp.) of silumin were revealed.
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Study of structural properties of bismuth pyrostannate by Raman and IR spectroscopy
Статья научная
Chromium-substituted bismuth pyrostannates with a pyrochlore structure were synthesized by the solid-phase reaction method. The X-ray structural analysis performed at room temperature showed that the samples Bi2(Sn1-xCrx)2O7, x = 0; 0.05, 0.1 are single-phase and belong to the Pc monoclinic structure. Polymorphic transformations of the synthesized samples were studied by Raman and IR spectroscopy. IR spectra were obtained at the temperature range 110–525 K and frequencies 350–1100 cm–1. Raman spectra were measured at room temperature at frequencies of 100–3000 cm–1. Heterovalent substitution of Sn4+ for Cr3+ modifies the spectra of pure Bi2Sn2O7. The crystal structure of Bi2Sn2O7 consists of two oxygen sublattices: SnO6 and Bi2O'. Chromium ions substituted tin ions in the SnO6 oxygen octahedra, distorting the local structure in the vicinity of bismuth ions. Phonon modes are softening in the vicinity of phase transitions. А shift of the phase boundaries of polymorphic transitions is observed for Bi2(Sn1-хCrх)2O7, x = 0.05, 0.1. The frequencies of stretching vibration modes were determined from IR and Raman spectra. The substitution of chromium for tin ions resulted in the appearance of two new modes at frequencies of 581 and 822 cm–1 in the Raman spectra. The absence of an inversion center in the crystal structure of Bi2(Sn1-xCrx)2O7 is confirmed by Raman spectroscopy. IR spectra of chromium-substituted samples consist of complex lines, which decompose into 2 and 3 Lorentzian lines. The softening and broadening of optical absorption modes are associated with the electronic contribution. Impurity states of electrons form polarons.
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The influence of prefinishing operations at titanium alloys on the characteristics of MAO coatings
Статья научная
Improving the reliability, service life and operational safety of titanium alloy structures exposed to thermal, chemical and mechanical stresses can be achieved by applying various protective coatings. One of the effective methods of protecting such alloys is the formation on their surface of oxide coatings that are resistant to external factors. Of great interest from this point of view is the method of micro-arc oxidation (MAO), which allows one to obtain multifunctional ceramic-like oxide coatings with unique properties. Such coatings can be used to create a durable heat and electrical insulating layer on parts, protect surfaces from erosion in high-speed gas flows, corrosion in aggressive environments and wear by friction, to increase the surface emissivity, etc. This method is well established for the oxidation of aluminum alloys. Despite the fact that the mechanism of coating formation during MAO is the same for aluminum and titanium alloys, there are certain differences in the structure and characteristics of the resulting coating. For example, it is believed that during the MAO treatment of aluminum alloys, preliminary surface preparation is not required and the adhesive strength is comparable with the strength of the substrate material. However, when processing titanium alloys, we noted cases of a significant decrease in adhesive strength. One of the reasons may be the lack of preliminary surface preparation before coating. Therefore, studies aimed at studying the influence of the method of surface preparation and the resulting roughness on the characteristics of the applied coatings are relevant.
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The magnetic anisotropy comparison of polycrystalline and single-crystal Fe3Si films
Статья научная
High-tech devices improvement requires development of technology and search for new materials from science. Currently, the development of the magnetism research field has reached a very broad knowledge, making it possible to create and study a variety of artificial ferromagnetic materials, which are already actively used in science and technology. The latest scientific knowledge shows that the same material in different states can exhibit different electrical and magnetic properties. Thus, thin magnetic films are actively used in modern devices. Physical processes in thin films proceed differently than in bulk materials. As a result, the film elements have characteristics that differ from those of bulk samples and make it possible to observe effects that are not characteristic of bulk samples. A film is a thin layer of a bound condensed substance, the thickness of which is compared with the distance of surface forces action; it is a thermodynamically stable or metastable part of a heterogeneous film-substrate system. Further researsh of film structures led to the creation and study of multilayer magnetic systems. In such structures, the presence of both various ferromagnetic materials layers and non-ferromagnetic interlayers is possible, and the multilayer systems properties can differ significantly from the properties of any system components. These materials also have many practical applications, including radio communications and geological exploration. In our experiment, ferromagnetic thin films of Fe3Si silicide were synthesized by molecular beam epitaxy with co-deposition of Fe and Si. A polycrystalline silicide film was obtained on a SiO2/Si(111) substrate, and a single-crystal film - on Si(111)7×7. The structure was investigated using the diffraction of reflected fast electrons directly during the growth process. The magnetic anisotropy of the obtained samples was studied applying the method of ferromagnetic resonance. It was found that the polycrystalline film is characterized by uniaxial magnetic anisotropy, which is 13.42 Oe and is formed as a result of “oblique” deposition, whereas the magnetic anisotropy for a single-crystal Fe3Si film is formed to a greater extent by internal magnetocrystalline forces.
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The process of nanomodifying cast aluminum alloy ingots for components of aerospace vehicles
Статья научная
Currently, increasing attention has been paid to such a class of materials as nanopowders (NP) of chemical compounds, which are ultra-thin formations of not more than 100 nm in size. Such attitude to these materials is explained by the fact that they have unique physical, chemical and mechanical properties significantly different from the properties of materials of the same chemical composition in a massive state, and these properties can be transferred to some extent from them or with their participation to the products. The existing methods of introducing NP into metal melts could not be used due to their special properties in comparison with coarse powders, and therefore a new method of their introduction into the melt was developed, excluding direct contact of NP particles with oxygen and unhindered penetration of particles into the melt through the oxide layer. The essence of the method was as follows. In the aluminum container filled up with aluminum particles or deformable aluminum alloys D1 or D16 and various NP (nitrides, carbides, oxides, etc.), and this composition was pressed into the rod, with its help NP was introduced into the melt during casting of aluminum ingots and deformable aluminum alloys. The results of the study showed that this excludes the appearance of cracks in the ingots, as well as improves their technological and mechanical properties.
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Статья научная
Today, protective coatings are applied to almost all parts and components of engineering products in order to ensure high performance properties of machines, with the lowest economic cost. The method of plasma spraying allows to apply heat-resistant coatings on a different kind of basis, in addition to a wide variety of materials. Therefore, rocket and space engineering is primarily interested in the method. In modern conditions of high rate of mechanical engineering development engineers must develop and put into operation products within the shortest possible period of time. As a rule, engineers select the modes of plasma spraying using the method of selecting the empirical relationship between the properties of the coatings and the values of the specified parameters of plasma spraying, which suggests conducting a huge number of experiments. That is why we see the need to find new methods for selecting the plasma spraying parameters, which are based on mathematical and analytical apparatus. We set the task to study and show the applicability and prospects of the proposed method. In the work we carried out the operations of spraying nichrome coating, at different values of the arc current. We studied the adhesive strength of the coatings obtained and their microstructure. We showed the relationship between the arc current and the adhesion of the coatings using their microstructure. These studies have made it possible to exclude a large number of experiments, which usually establish an empirical relationship between the values of the input parameters of the deposition process and the values of the characteristics of the coatings obtained. In the future, we assume that the database of such relationships will make it possible to fully use this method in engineering industries.
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Статья научная
The most important resource for improving the performance of parts is the reduction of the surface roughness. One of the promising ways to reduce the surface roughness is the abrasive extrusion processing. When developing the AEP technology, it is necessary to know the flow rate (pressure) of the WE, which depends on the viscosity of the latter. In turn, the viscosity of the WE is determined by its temperature. The temperature of the working environment at AEP can be calculated if the coefficients of thermal conductivity and thermal diffusivity of the WE are known. The working environment for AEP consists of two components, therefore, the coefficient of thermal conductivity can be calculated by known formulas. However, the calculation error is significant, therefore, the experimental determination of the abovementioned coefficients is required. The installations for the coefficients research have been presented, the methods of conducting experiments have been developed. After mathematical processing of the experiments results by means of the AdvanceGrapher v. 2.11, the dependences of the thermal conductivity and thermal diffusivity on the abrasive concentration have been obtained. The studies of the thermophysical properties of the working environment have shown that the values of thermal conductivity and thermal diffusivity of the WE are mainly determined by the concentration of abrasive grains in the working environment. The direct dependence of these coefficients on the degree of filling the working environment with abrasive grains has been established.
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Статья научная
In the production of space rocket technology, electrochemical processes are used, as a result there is pollution of sewage by metal ions. The strict requirements of environmental authorities do not allow sewage, containing metal ions with concentration exceeding the maximum permissible values, to be discharged directly into reservoir or sewers. The greatest difficulties are caused by the purification of water from hexavalent chromium. The proposed methods for purifying from hexavalent chromium, electrocoagulation method, galvanocoagulation method, sorption methods, combined methods, have some disadvantages, such as: significant energy consumption, significant consumption of soluble metal anodes, passivation of the anodes, need for large excesses of reagent (iron salts), large amounts of precipitate and the complexity of its dehydration, high cost and scarcity of sorbents, high consumption of reagents for the regeneration of sorbents, and others. This work shows equipment for experiments, including a diaphragm electrolyzer with a coaxial arrangement of electrodes. Formulas for calculating the chromium ions flux due to migration and diffusion are presented. The difference between the calculated amperage from the practical one is 25 %, and the theoretical degree of purification from the real one is 4 %, which confirms the effectiveness of the proposed cleaning method. The concentration of chromium anions was determined by atomic absorption spectroscopy. The degree of purification of water from chromium ranged from 84 to 96 %. The highest degree of purification (96 %) was obtained with an electrolysis duration of 29 minutes.
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