Proceedings of the National Academy of Sciences of Belarus, Physical-Technical Series / Известия Национальной академии наук Беларуси. Серия физико-технических наук
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Фазовый состав, микроструктура и микротвердость сплава In–Sn, полученного высокоскоростной кристаллизацией
Get PDFThe results of studying of the structure and properties of the In – 42 at.% Sn alloy in the form of foil obtained by the method of rapid solidification with a cooling rate of the melt of at least 105 K/s are presented. X-ray diffraction analysis showed that the phase composition of the alloy corresponds to the equilibrium state diagram. Foils consist of an InSn4 compound (γ-phase) and an In3Sn compound (β-phase). The grain structure of foil was studied by electron backscatter diffraction technique. It is established that the foil have a microcrystalline structure. The parameters of the microstructure are determined by the method of random linear secants: the volume fraction of the phases, average chord length of the random linear secant on the inclusions of each phase, the specific surface of the interface. Microstructure and distribution of components was also studied for both foil surfaces. The texture of both phases of the polycrystalline foils was studied by the method of inverse pole figures. It is established that the initial foils of the investigated alloy are in an unstable state. It is shown that an increase in the microhardness of the alloy during aging and annealing caused by change in the parameters of the grain structure.Исследования направлены на получение перспективных для бессвинцовой пайки легкоплавких сплавов в виде фольги с однородным распределением дисперсных составляющих. Представлены результаты изучения структуры и свойств сплава In – 42 ат.% Sn, полученного методом сверхбыстрой закалки из расплава при скорости охлаждения расплава порядка 105 К/с. Рентгеноструктурные исследования показали, что быстрозатвердевшая фольга состоит из соединения InSn4 (γ-фаза) и соединения In3Sn (β-фаза), что соответствует равновесной диаграмме состояния. По экспериментальным данным, полученным методом дифракции отраженных электронов (ДОЭ), определены параметры фаз с использованием метода случайных секущих: объемная доля фаз, средняя длина хорд случайных секущих на выделениях каждой из фаз, удельная поверхность межфазной границы. Микроструктура и распределение компонент изучались с помощью растровой электронной микроскопии и рентгеноспектрального анализа. Вид микроструктуры существенно различается для стороны, прилегающей к кристаллизатору, и свободно затвердевающей. Методом ДОЭ установлено, что сплав In – 42 ат.% Sn, полученный высокоскоростной кристаллизацией, состоит из основной β-фазы и дисперсной γ-фазы, имеющих микрокристаллическую структуру с размером зерен, не превышающим 2 мкм. Методом обратных полюсных фигур изучена текстура обеих фаз, составляющих полученные поликристаллические сплавы. Проведены исследования механических свойств как сразу после изготовления фольги, так и после старения и отжига. Показано, что увеличение микротвердости сплава при старении и отжиге обусловлено изменением параметров зеренной структуры
РЕШЕНИЕ 3D-ЗАДАЧИ КОМПЬЮТЕРНОЙ ТОМОГРАФИИ ПО ИЗВЕСТНЫМ ТОМОГРАММАМ НА СИСТЕМЕ ПРОИЗВОЛЬНЫХ ПЛОСКОСТЕЙ
Get PDFThe article is based on restoration method for the internal structure of a three-dimensional body using polynomial interflatation based on known tomograms (traces) lying on a system of arbitrary planes, which is a generalization of the method of body restoration with its known tomograms on a system of three groups of parallel planes. A definition of tomograms in the mathematical sense has been provided and the algorithm of transition of tomogram images into the functional dependence has been outlined.Theorems on interflatation properties and errors of the built operator have been formulated and proved. A test case for the construction of the interflatation operator for the quadratic function has been demonstrated, and the computational experiment involved the development of a number of programs in MathCad. The experiment has provided visualization results for an exact solution and a solution obtained experimentally for the case when the exact function is known. It has been shown that the constructed structure approximates this function exactly, which is not the case of classic interpolation operators.The suggested method makes it possible to solve the problem of three-dimensional computer tomography for a fundamentally new data collection scheme. For example, it permits the use of the fan scheme for data collection in each of the planes in which the tomograms lie.
ПРОГНОЗНАЯ ОЦЕНКА ДОЗОВЫХ НАГРУЗОК НА ПЕРСОНАЛ ТИПОВОЙ АЭС-2006 ПРИ ПРОЕКТНЫХ АВАРИЯХ С УЧЕТОМ ИНФРАСТРУКТУРЫ ПРОМПЛОЩАДКИ
Get PDFAssessment of radiation effect on nuclear power plant staff was made for design basis accident. The considered accident scenario includes spent fuel assembly drop into the reactor core or fuel pool during load-unload operations with fuel assemblies damage and radionuclide emission. The proposed method included the assessment of radionuclide sedimentation on characteristic surfaces of nuclear power plant site, calculations of radioactive aerosol distribution depending on the distance of emission source in COMSOL 3.5 program. The software module is based on highly detailed account of the infrastructure of the nuclear power plant industrial site according to the master plan, which allows obtaining more accurate estimation of radioactive substances deposition and, as a result, more accurate calculation of doses for staff and population. The assessment of average volume activity in lower air layer on site during VVER design basis accident is performed. Doses from radioactive cloud (external exposure) and from inhalation (internal exposure) were estimated for following radionuclides: 137Cs, 131I, 133I, 90Sr. In the case of the design basis accident associated with the fall of the assembly during fuel load-unload operations the received value of the total effective dose of staff exposure is 7.80 mSv for the first 8 hours after the accident beginning. This number is well below the threshold of the allowable annual dose limit for personnel in emergency situations (50 mSv).
ДИНАМИКА ПЕРЕХОДНЫХ ПРОЦЕССОВ В ПРИВОДАХ С ГИБКОЙ СВЯЗЬЮ ПРИ РАЗДЕЛЕНИИ ПОЛУПРОВОДНИКОВЫХ ПЛАСТИН НА КРИСТАЛЛЫ АЛМАЗНЫМ КРУГОМ
Get PDFPossibilities of increase of cutting speed at simultaneous increase of accuracy of coordinate movements and decrease of dynamical loads at initial, the most dangerous from emergence of chips and breakages, moment of interaction of 15–120 microns thick diamond wheel with a wafer having 250–500 microns thickness and diameter of 50–250 mm, at its chipping are shown. The table with a wafer makes reciprocal coordinate cyclic movements at cutting. In the course of its acceleration to working feed rate there are mechanical oscillations in the direction of driving, which have natural frequency. These oscillations can lead to a table deviation from the machine coordinate and to occurance of accelerations, significantly differ with predicted ones, at achievement of working feed rate and subsequent contact of a wafer with a diamond wheel. That can be considered at realization of a production cycle, and, in some cases, oscillations can be operated programmatically by the choice of rational ratios of values of working stroke, length of non-working stroke and free frequency that allows reducing or exclusion of chips and breakages of wafers and diamond wheel, reducing their thickness and increasing processing speed by 1,5–2 times. Possibilities of creation of combined system of drives which use allows exclusion emergence of mechanical oscillations are shown
ИНТЕГРАЛЬНЫЙ МЕТОД РЕШЕНИЯ ЗАДАЧ ТЕПЛОПРОВОДНОСТИ С ГРАНИЧНЫМ УСЛОВИЕМ ВТОРОГО РОДА. 1. ОСНОВНЫЕ ПОЛОЖЕНИЯ
Get PDFПолучение алюмоматричного композиционного материала, модифицированного наноструктурным кубическим нитридом бора
Get PDFThe structure and microhardness of an aluminum alloy with additives of nanostructured cubic boron nitride (cBN) after treatment under high pressure and temperature are investigated. А nanostructured powder of cBN with primary particles within 50–200 nm is used as a filler. A preliminary chemical-thermal modifying of the nanostructured cBN, which consists in its high-temperature annealing in the temperature range of 750–950 °C in a medium of aluminum-contai ning compounds, is carried out to increase the chemical affinity of the nanostructured cBN to the aluminum matrix. It is shown that the modifying of nanostructured cBN with aluminum increases the strength of the additives retention in the aluminum matrix. At the same time the increase in the concentration of BN additives from 1.5 to 5 wt.% as well as the increase in the treatment temperature at a fixed pressure promotes the increase in the microhardness of the material by a factor of 1.5 to 2 as compared with the base aluminum alloy without the addition of a modifier. An increase in the cBN concentration to 5 % by weight results in an increase in the fraction of smaller particle conglomerates (1–5 μm) in the material and in a decrease in the size of large inclusions to 10–20 μm. In this case, the distribution of BN particles in the aluminum matrix is more uniform in comparison with a material with a cBN content of 1.5 wt.%. In the material with the growth of temperature up to 1000 °С, cBN in aggregates is recrystallized with the formation of single-crystal (polycrystalline) particles with the size of 1–10 μm with faceting specific for cBN micron particles.Проведено исследование структуры и микротвердости алюминиевого сплава с добавками наноструктурного кубического нитрида бора (cBN) после обработки в условиях высоких давлений и температур. В качестве наполнителя применяли наноструктурный порошок сBN с размером первичных частиц в пределах 50–200 нм. Для повышения химического сродства наноструктурного cBN к алюминиевой матрице проведено предварительное химико-термическое модифицирование наноструктурного cBN, заключавшееся в его высокотемпературной обработке (отжиге) в диапазоне температур 750–950 °С в среде алюмосодержащих соединений. Показано, что модифицирование наноструктурного нитрида бора алюминием способствует прочности удержания наполнителя в алюминиевой матрице. При этом увеличение в шихте концентрации наполнителя BN от 1,5 до 5 мас.%, а также повышение температуры обработки при фиксированном давлении способствует возрастанию микротвердости материала в 1,5– 2 раза по сравнению с базовым алюминиевым сплавом без добавок модификатора. Повышение концентрации BN до 5 мас.% приводит к увеличению в материале доли более мелких конгломератов частиц (1–5 мкм), уменьшению размеров крупных включений до 10–20 мкм, при этом распределение включений из частиц BN в алюминиевой матрице более равномерное по сравнению с материалом, содержащим 1,5 мас.% cBN. С ростом температуры до 1000 оС в материале происходит рекристаллизация cBN в агрегатах с образованием его отдельных монокристаллических (поликристаллических) частиц размерами 1–10 мкм, обладающих огранкой, характерной для микрочастиц cBN
РЕКУРРЕНТНАЯ ЛИНЕЙНАЯ ФИЛЬТРАЦИЯ СЛУЧАЙНЫХ ДИНАМИЧЕСКИХ ПОЛЕЙ В УСЛОВИЯХ АПРИОРНОЙ НЕОПРЕДЕЛЕННОСТИ
Get PDFThe task of filtering random dynamic fields is relevant for a number of applications. To solve it, one can use a statistical approach based on the Kalman filter theory. Because of large dimension of the images, this leads to complicated equations and requires large computational costs, which makes it difficult to solve the problem in real time. Instead of statistical, it is suggested to use a deterministic approach based on the recursive least-squares technique. It is assumed that the field model, its covariance characteristics, as well as the model and characteristics of the measurement results are a priori given. To obtain recursive filter equations the loss function is used, which consists of two parts. The first one is the quadratic residual functional of the solution with weight in the form of an inverse covariance measurement matrix. The second one is a quadratic functional of the difference between the current estimation and its extrapolation to the next time point. As a result, an optimal filtering algorithm is obtained in an explicit form, which can be realized in real time with significantly less computational costs compared to the Kalman filter. An equation for the variance of filtering errors is obtained, that allows estimating the accuracy of the proposed filter and its comparison with the accuracy of the Kalman filter. An example of using the proposed methodology is given.
ПОЛУЧЕНИЕ ВЫСОКОПРОЧНЫХ ДЕФОРМИРУЕМЫХ АЛЮМИНИЕВЫХ СПЛАВОВ ТИПА АМг10
Get PDFTraditional grades of aluminum alloys do not always meet the requirements of modern aerospace engineering. Al–Si foundry alloys possess insufficient mechanical strength characteristics and low plasticity due to their structural features (coarse brittle silicon inclusions and intermetallic phases). Therefore they cannot be exposed to pressure treatment. A technique for producing high-strength aluminum alloys, which consists in obtaining ring blanks by means of direct crystallization of melts with application of non-stationary centrifugal force fields and simultaneous introduction of modifiers, is proposed. The microstructure and plasticity of resulting tube-shaped blanks allow them to be exposed to sheeting for subsequent production of pipe workpieces with mechanical strength commensurate with mechanical strength of structural steel. The technique involves hydrothermal synthesis of nanostructured particles of aluminum oxide, which are overheated above the melt temperature prior to introduction into the molten aluminum alloy. This procedure enhances the processes of intercrystalline hardening with minimal fluctuations of internal stresses within the hardened material. The materials have tensile strength of up to 380 MPa (before modification by nanodispersed aluminum oxide it was 210 MPa). The microstructure has showed changes in the acicular dendrite component, which tends to become more dispersed and equiaxial. Eventually this leads to an increase in the mechanical strength by a factor of 1.25–1.32.
ОПТИМИЗАЦИЯ РЕЖИМА НАГРУЖЕНИЯ ПРИ СКОРОСТНОМ УДАРНОМ ВЫДАВЛИВАНИИ БИМЕТАЛЛИЧЕСКИХ ПЛОСКОСТУПЕНЧАТЫХ СТЕРЖНЕВЫХ ИЗДЕЛИЙ
Get PDFМОДЕЛИРОВАНИЕ ВЗАИМОДЕЙСТВИЯ ЭЛЕКТРОМАГНИТНЫХ ВОЛН С АНИЗОТРОПНЫМИ СРЕДАМИ НАД УГЛЕВОДОРОДНЫМИ ЗАЛЕЖАМИ В РЕЖИМЕ ВИДЕОИМПУЛЬСНЫХ СИГНАЛОВ
Get PDFThe article presents the simulation of the interaction of electromagnetic waves in the mode of video pulse signals with the medium over hydrocarbon deposits. The analysis of the spectra of reflected video pulse signals from the medium over hydrocarbons is carried out. A study of the propagation of radio waves over hydrocarbons is carried out within the framework of a quasihydrodynamic approximation. The choice of the frequencies of video pulse signals is due to the determination of media characteristics over deposits at great depths compared to the surface of the earth. The spectrum of reflected signals from an anisotropic medium above a hydrocarbon deposit in the mode of video pulse signals can be used to determine the electrodynamic characteristics of the medium over the deposit over a wide range of frequencies of probed signals, dielectric permittivities and conductivity of media. The ability to reconfigure a geo-prospecting device from one mode to another (pulse width adjustment) in the presence of a deposit complements the functionality to search for hydrocarbon deposits. Electromagnetic methods for the search for and identification of hydrocarbons can be improved by obtaining information about objects through several information channels, which allows them to be identified with a sufficiently high level of reliability on the background of the underlying environment. The depths of occurrence, the resolving power in the investigated frequency range are determined. The results of the research can be used to develop new electromagnetic methods for the search for hydrocarbon deposits.Приводится моделирование взаимодействия электромагнитных волн в режиме видеоимпульсных сигналов со средой над углеводородными залежами. Осуществлен анализ спектров отраженных видеоимпульсных сигналов от среды над углеводородами. Исследование распространения радиоволн над углеводородами проводится в рамках квазигидродинамического приближения. Выбор частот видеоимпульсных сигналов обусловлен определением характеристик сред над залежами на больших глубинах по сравнению поверхностью Земли. Спектр отраженных сигналов от анизотропной среды над углеводородной залежью в режиме видеоимпульсных сигналов может быть использован для определения электродинамических характеристик среды над залежью в широком диапазоне частот зондируемых сигналов, диэлектрических проницаемостей и удельных проводимостей сред. Возможность перестройки устройства георазведки с одного режима на другой (регулировка длительности импульса) при наличии залежи дополняет функциональные возможности для поиска углеводородных залежей. Электромагнитные методы поиска и идентификации углеводородов могут быть усовершенствованы за счет получения информации об объектах по нескольким информационным каналам, что позволяет с достаточно высоким уровнем достоверности выделять их границы на фоне подстилающей среды. Определены глубины залегания, разрешающая способность в исследуемом диапазоне частот. Результаты исследований могут быть использованы для разработки новых электромагнитных методов поиска углеводородных залежей