Статьи журнала - Siberian Aerospace Journal
Все статьи: 151
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
Today, the scope of application of electric propulsion systems for orbit correction and spacecraft’s attitude control is rapidly expanding due to their high efficiency compared to liquid jet systems. The main elements of electric jet systems are plasma or ion thrusters. To ensure power supply of such thrusters, complex electronic power processing systems – power processing units (PPU) – are used. These units are capable to operate for a long time (up to 15 years or more) in a high vacuum environment and generate sufficiently high accelerating voltages – from 300 V and higher. PPU’s comprise various EEE-parts, mainly in the case design. As a rule, the technology of their production is such that air or nitrogen is initially located inside the housing at atmospheric pressure. During the operation of the unit, the non-absolute hermeticity causes pressure decrease inside EEE housings. Due to high voltages applied, this can lead to electrical breakdowns between current-carrying ele-ments inside the parts, their failure with the subsequent failure of the functional blocks of the unit. The paper considers the physical principles of the breakdown occurrence inside EEE-parts cases. The results of non-hermiticity measurements of several types of HV EEE-parts are presented. The dynamics of the pressure drop to the values dangerous from the point of view of breakdown event and the relevant occurrence duration are esti-mated. It is shown that duration of being exposed to the pressure-dangerous conditions can be as long as space-craft service lifetime. It can make difficult to use packaged gas-filled EEE-parts at the level of units intended to operate in non-pressurized compartments of spacecraft. Recommendations are provided for selecting the design of EEE parts with an operating voltage of about 300 V or more, as well as circuit solutions used to develop high-voltage equipment intended to operate in vacuum environment.
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The use of the inverse transformation method for time series analysis
Статья научная
In modern conditions of technology development, signs of systemacity are manifested to one degree or another in all areas, so the use of system analysis is an urgent task. In this case, the main factors in this situation are data processing and prediction of the state of a system. Mathematical modeling is used as a prediction method for a given subject area. A mathematical model is a universal tool for describing complex systems representing the approximate description of the class of phenomena of the external world expressed by mathematical concepts and language. The mathematical model can be represented as a set of systematic components and a random component. In this article, the object of prediction is the irregular random component of a model, which reflects the impact of numerous random factors. The origin, nature and laws of variation of the random variable are known, therefore, to simulate its behavior or predict its future value, one needs high degree of certainty to establish the form of continuous distribution function of the random variable. The empirical distribution function is calculated using the sample of random variable values. This empirical function is close to the values of the desired unknown function of distribution. The resulting empirical function is discrete, therefore it is necessary to apply piecewise linear interpolation to obtain a continuous distribution function. The predicted random component of time series has been included in the initial regression model. In order to compare augmented and initial regression models, several values were excluded from the time series and new prediction was built. The value of the average approximation error for assessing the quality of the model is calculated. The augmented regression model proved to be more effective than the original one.
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Статья научная
Ensuring high reliability of unique high-critical products at the design stage is an actual task that the aerospace industry faces. For high reliability indicators, at the design stage, it is necessary to ensure the basic property of the product – its strength, with a high probability of non-destruction. It is provided by introducing the corresponding coefficients – «safety coefficient» and «margin of safety» into the strength calculations. The necessity in these coefficients is based on the spread of values of external loading factors: magnitude of forces, combination of forces, kind of actions, place of connection, etc. In this case, the safety coefficient is related to external factors. The margin of safety refers to internal factors: the spread of the mechanical characteristics of the product material, the spread of the geometric dimensions of the product, etc. To determine, with a given probability, the safety coefficient and margin of safety, it is necessary to know their dependence on the combination of spread of external and internal factors. The purpose of this work is to determine the mathematical connection between the internal factors of the spread and the safety coefficient, external factors of the spread and the margin of safety, the combination of these factors and the probability of non-destruction of structures. In this work the values of internal and external factors, which affect the strength and probability of non-destruction of the product and have the boundaries of the spread of their values, using the tools of probability theories, were characterized as random variables, the values of which are determined by the distribution density, expected value and variance. I this work there was found a high dependence of the product strength on the spread of its geometric characteristics and tools were defined to determine the total spread of the values of the main strength characteristics of the product with a given probability of non-destruction. The practical significance of the results of this work can be achieved in the aerospace industry, in particular, at the design stage of unique high-critical products.
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To the question of forecasting the technical condition of low-thrust liquid rocket engines
Статья научная
In the rapidly developing space and rocket industry, spacecrafts are being equipped with low-thrust liquid rocket engines. Нigh requirements are imposed on the reliability, efficiency and economy of fuel use for this type of rocket engine. To ensure monitoring of the characteristics of spacecrafts, a functional diagnostic system is used, which includes telemetry and analytical data processing. Telemetry performs the functions of receiving and transmitting information. Information processing is carried out in computer centers located on the spacecraft and the Earth. The most promising computing tool capable of predicting time series and classifying a large amount of interconnected data is considered an artificial neural network. In this regard, the subject of research in the work is data processing methods based on an artificial neural network. The purpose of the work is to develop a method for forecasting the technical condition of low-thrust liquid rocket engines using an artificial neural network. The relevance of research on the use of a neural network in the system of functional diagnostics of low-thrust liquid rocket engines for spacecraft is explained in the introduction. In the main part, an analysis of many telemetric data of the rocket engine is carried out and their strength in the forecast of the main diagnostic parameters is determined. It is proposed to use traction, specific impulse, and temperature of the structure as diagnostic parameters. The prognostic capabilities of the neural network were investigated and a schematic diagram of a method for predicting the technical condition of a low-thrust liquid rocket engine was developed. In the developed method, at the first stage, the neural network performs the approximation of the function and extrapolates the time series of telemetric data; the second stage determines the probable class of the technical condition of the engine. The conclusion outlines a plan for further experimental research in the study area and provides recommendations on the development and improvement of algorithms for functioning of artificial neural networks as part of the functional diagnostics system of the spacecraft. Due to the generalized nature of the methodological schemes, the results of the work can be applied to any type of rocket engines and used at all enterprises of the rocket and space industry of the corresponding profile.
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To the task of controlling a group of objects on the basis of information technologies
Статья научная
To participate the TPP with cross-section communications in the general primary frequency control, it is necessary to have a working main regulator. The main regulator is designed to maintain the steam pressure in the major steam line of the TPP at a given level, which is a difficult task. At the TPP with cross-connections, the steam produced by the boilers enters the major steam line. To maintain the pressure in the major steam line, it is necessary to control the heat load of the working boilers. Traditional solutions to construct the main regulator found no use, as have a number of disadvantages, not allowing exploiting a system of automatic control. Looking at the steam pressure control system in the major steam line from the bottom to up, it is possible to identify disadvantages that prevent the effective operation of the main regulator at each level. At the lower level of the main regulator, there are controllers of heat load of boilers, built according to the scheme task-heat. Heat load controllers are designed to maintain heat release in the boiler furnace at the required level. The heat signal is the sum of the signals for the steam flow of the boiler and the rate of change in the steam pressure in the boiler drum. Such a structure does not allow maintaining the invariance of the heat signal under external disturbances effectively, as sharp changes of the steam pressure in the major steam line lead to a "false" operation of the controllers. At the upper level there is the main regulator itself, which maintains the steam pressure in the major steam line at a given level and corrects the tasks to the controllers of the heat load of the boilers. The simultaneous identical effect on the heat load of the boilers cannot be optimal from the point of view of the criteria for assessing the quality of regulation, since the dynamic properties of the boilers, such as the gain, the transition time constant and the transport delay are individual for each boiler. However, in 2006–2008, the attempt to build an updated main regulator that takes into account the shortcomings of the traditional scheme was made. The basis of the structure of the main regulator is still parametric and, as a result of ten-years’ experience, shortcomings in the operation of the updated main regulator were identified. The shortcomings, in most cases, consist in need of frequent corrections of adjusting coefficients of system because of the change of dynamic properties of an object during the operation. In fact, the same problems related to the parametric structure of the regulator remain. Up-to-date information technologies made it possible to introduce adaptive process control systems that allow to count an extended number of signals entering the system and to form control actions, based on both current and historical data of the technological process. The use of the latest information technologies and modern hardware in the control of complex multi-connected units that solve not only the problems of process control, but also the problem of improving the economic and environmental performance of enterprises, should become a new step in the development of automatic control systems.
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Torsion of prismatic orthotropic elastoplastic rods
Статья научная
Conservation laws were introduced into the theory of differential equations by E. Noether more than 100 years ago and are gradually becoming an important tool for the study of differential equations systems. Not only do they allow you to qualitatively investigate the equation, but, as the authors of this article show, they also enable you to find exact solutions to the boundary value problems. For the equations of the iso-tropic theory of elasticity, the conservation laws were first calculated by P. Olver. For the equations of the theory of plasticity in the two-dimensional case, the conservation laws were found by one of the authors of this article and used to solve the main boundary value problems of the plasticity equations. Later it turned out that the conservation laws can also be used to find the boundaries between elastic and plastic zones in twisted rods, bent beams, and deformable plates. The proposed work found conservation laws for equations describing the orthotropic elastic state of the twisted straight-line rod. It is assumed that the remaining current depends linearly on the voltage tensor component. In the workit was also found an endless series of laws of preservation, which allows you to find an elastic-plastic boundary, which arises when twisting the orthotropic rod.
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Using signals of navigation satellites in the monitoring of the Earth covers
Статья научная
The features and capabilities of remote sensing of earth covers by means of signals of navigation satellites are presented. The methods of reflectometry of the surfaces of earth covers and radioscopy of forest canopy are described. The options for using the signals of GLONASS, GPS systems are considered. Test measurements of interference diagrams were carried out on 5 test platforms from heterogeneous soil surfaces: salt marshes and asphalt; water surfaces of saline and freshwater bodies in summer, including ice cover of small thickness in the period of autumn freeze-up. The method of radioscopy helped obtain the data on the spatial and temporal characteristics of attenuated signals of the GLONASS and GPS satellites in the pine forest. Estimates of the linear attenuation coefficients of the signals passing through a forest canopy with a coordinate reference were made. The results obtained are the basis for the development of methods and technologies for continuous monitoring of the characteristics and state of earth covers by means of signals of navigation satellites for solving a wide range of applied tasks.
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Volume temperature control at automated high-frequency processing of polymer and composite materials
Статья научная
The purpose of this work is to develop and justify a method for volumetric temperature control of a polymer and composite material in automated high-frequency processing. The developed method is implemented by in-troducing thermocouples into the prism-shaped or cube-shaped sample body according to a certain pattern of their location throughout the volume. This technique is cost-effective and easy to implement compared to expen-sive and specialized equipment with complex design, as well as to the cost of thermocouples having a simple de-sign. Methods to achieve the purpose of the research of the contact method of volumetric temperature of a polymer or composite sample control are development and outlining thermocouples throughout the volume so as to iden-tify the most accurate temperature spectrum of the polymer or composite sample during automated high-frequency processing. Another method to achieve this purpose is the method of finding out how it will affect the measurements accuracy of the heating sample temperature from the introduction of thermocouples by making holes in it for installation. For this, a finite-difference mathematical calculation of the dependence of the sample temperature on the number of holes for thermocouples in it was performed in the MSC Patran Sinda software package. The calculation results were summarized and presented on graphic data. Further, a general mathemat-ical calculation was performed according to the formulas for the process of heat and mass conductivity calcula-tion, the results of which were table and graphic data. At the end of the finite-difference and general mathematical calculation, a comparative analysis of the ob-tained error of temperature measurement from the introduction of thermocouples into the body of the sample was performed. Based on this analysis, the developed method is applicable for further research on automated high-frequency processing of polymer and composite materials, since the errors obtained do not exceed the permissi-ble 3 %.
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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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