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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МОДЕЛИРОВАНИЕ ПРОЦЕССОВ ДИФУЗИОННОГО ВЗАИМОДЕЙСТВИЯ ПРИ СПЕКАНИИ ПОРОШКОВЫХ МАТЕРИАЛОВ С ИСПОЛЬЗОВАНИЕМ ГИДРОДИНАМИЧЕСКОЙ ТЕОРИИ СМАЗКИ
Get PDFPowder material is a certain set of particles capable of plastically deforming both due to plastic shear of this set of particles, and due to sliding of the same set of contacting particles relative to each other. Making simulation, we proceeded from the fact that the model must have a finite number of features from the number inherent in the original object. At the same time, some of the properties of the object, when transferred to the model, could undergo a number of changes, which, having had insignificant effects on the object under study, could substantially simplify its theoretical-model representation. Using the structural model of diffusion interaction in powder materials, the process of densification and inelastic deformation of powder materials is described under the condition of plasticity using the liquid-dynamic theory of lubrication in a closed volume. Based on this, a theoretical analysis of the mechanism of sintering particles of iron-based powder materials was carried out. The effect of plasticizer introduction at different stages of product manufacturing on the basis of the proposed models of powder metallurgy processes is considered. The results of the scientific publication can be used in experimental studies of diffusion processes in the formation of powder materials and the choice of technological regimes
МОДЕЛИРОВАНИЕ И ОПТИМИЗАЦИЯ ПРОЦЕССОВ ФОРМОВАНИЯ МАКАРОННЫХ ИЗДЕЛИЙ В КАНАЛАХ МАТРИЦ СТУПЕНЧАТО-ПЕРЕМЕННОГО СЕЧЕНИЯ
Get PDFCurrently velocity unevenness of forming pasta matrix over the cross section is an unsolved problem, both in domestic and in international practice.The construction of the matrix is one of the key factors influencing technical and economic indicators of pressing work. The matrix includes a cylindrical body with wells located on concentric circles, liners mounted within wells, shaping with through holes that are grouped in the nests.The aim of the work was to develop a methodology and establish it by the ratio between plastic and viscous components of the total hydrodynamic resistance in the flow of pasta dough in the channel of step-variable cross-section. The technique of determining the minimum pressure of the molding that is required to overcome the yield stress in shear (ultimate shear resistance) pasta in the channel of circular, annular, rectangular and arbitrary cross-sections, is developeds. Computational evaluation of this pressure in the molding of the dough of first and higher grades and test on the basis of polyrope used for industrial types and sizes of channels with stepped variable cross-section is made. It is shown that in general the hydrodynamic resistance is dominated by the contribution of the component due to viscous shear deformation in the course. An approximate method of estimating the speed and power of flow parameters pasta in the channels of step-variable cross section using the model of Bingam is proposed. The research results can be used in the design of the forming equipment, as well as in the development of methods of calculation of processes of formation and pasta dough
ВЫБОР ПАРАМЕТРОВ ОПРЕДЕЛЯЮЩИХ УРАВНЕНИЙ ПРИ ТЕЧЕНИИ НЕЛИНЕЙНО УПРУГОПЛАСТИЧЕСКОГО МАТЕРИАЛА
Get PDFThe question of the choice of two scalar parameters, respectively, the two defining equations of the flow of the particular model of a nonlinear elasticity-plasticity to limit the growth of elastic anisotropy is considered. The elastic properties of the material are described by the generalized Murnaghan law of elasticity. The model is constructed with the assistance of the potentiality principle of defining equations in the stress rate, which lets determine the yield surface deviator cross-section. To simplify the case the material assumed to be perfectly elastic-plastic. The values of the first and second parameters are relative parts of dissipative specific deformation power and projections on the surface of deviator section of yield surface of criterion deviator operator. They are part of the differential equations for determining a specific potential energy of elastic deformation and the Cauchy stress tensor. In the case when the first parameter is independent on the strain rate tensor, the system of equations generates the minimum value of the parameter. This choice makes too large errors in the condition of biaxial state of stress in numerical modeling of Bridgman’s experiments under biaxial compression. The value of the second parameter has to be substantially smaller. The first parameter is chosen while carrying out of this requirement when the first parameter depends on the angle between the normal vector to the surface deviator section and “vector” of strain rate (in basic, epitaxial experiments). The choice of these parameters significantly limits the growth of elastic anisotropy, as it is shown by numerical simulation of biaxial loading. It can be updated by use of additional experimental data of these loadings
ВОЗБУЖДЕНИЕ КОЛЕБАНИЙ ШЕПЧУЩЕЙ ГАЛЕРЕИ В ДИСКОВОМ ПЛАНАРНОМ ДИЭЛЕКТРИЧЕСКОМ РЕЗОНАТОРЕ ЩЕЛЬЮ СВЯЗИ
Get PDFThe spectral and energy characteristics of disk planar dielectric resonator (DR) with high-order whispering gallery modes (WGMs) were investigated in Ka-band. The diameter of the planar DR was several wavelengths in the dielectric material, and its height was much smaller than the wavelength. The dielectric disk was placed by flat bases between two conducting mirrors. Thus, electromagnetic field of the resonator was limited by the height of the planar disk by two conducting surfaces. The resonant properties of such structure were determined by the condition of total internal reflection of the waves from the curved surface of the dielectric disk. A method of effective excitation of WGMs in the planar DR by the coupling slot in the metal mirror was proposed. It is shown that with this excitation method, a regime of supercritical coupling with planar DR is achieved. In this case, the mode spectrum of such a resonator is rarefied relatively. It is established that the Q-factor of a planar DR is mainly determined by the losses in its dielectric material and by the ohmic losses in metallic mirrors, since the radiation losses at a necessary ratio of the wavelength and the diameter of the dielectric disk can be small. For a disk made of teflon with a height of 1 mm, a diameter of 78 mm, located between brass mirrors, the Q-factor of the planar DR can reach 1500 at the high-frequency edge of the Ka-band. The recommendations for increasing of Q-factor of the planar DRs and reducing their dimensions are proposed
МЕТОДИКА ПОДГОТОВКИ МНОГОМАССОВЫХ КОМПЬЮТЕРНЫХ МОДЕЛЕЙ К ВЕРИФИКАЦИИ
Get PDFCoefficients calculation methods for systems of differential equations are developed. These coefficients are calculated by the results of multimass model elements displacement function and loading function measurements obtained during bench tests.The obtained results can be used for verification of complex mechanical systems, models and finite element models of rod structures.Разработаны методы идентификации параметров математических моделей по результатам стендовых и натурных испытаний механических конструкций. Исходными данными для вычисления параметров дифференциальных уравнений, описывающих динамику колебаний многомассовых моделей, являются измеренные в ходе эксперимента функции перемещения и нагружения. Получены формулы для вычисления коэффициентов упругих и демпфирующих элементов, объединяющих колеблющиеся массы в единый механизм. Результаты работы могут быть использованы при моделировании многомассовых колебательных систем, работающих в режиме свободных колебаний или с закрепленными граничными элементами
ЭКРАНИРУЮЩИЕ СВОЙСТВА ОПТИЧЕСКИХ ПОКРЫТИЙ, ПОЛУЧЕННЫХ НА СТЕКЛЯННЫХ И ПОЛИМЕРНЫХ МАТЕРИАЛАХ
Get PDFCoatings In2O3 + SnO2 (ITO) and ZrO2 – Ni – ZrO2 – Cu – Ni – ZrO2 deposited on glass and polymer substrates, are presented. Their shielding properties in the optical and radio frequency wavelength ranges have been studied. Samples with coatings 120(In2О3 +SnО2 ) and 90ZrO2 /8Ni/90ZrO2 /22Cu/5Ni/35ZrO2 have good shielding properties (98 % of electromagnetic emission is reflected in the range of 0.7…17 GHz). ITO-coating has low surface resistance of 8…9 ohms/ square per square in combination with high light transmittance (T ~ 90 %). However, in order to achieve these properties one needs to heat the substrate up to 300…400 °C. The coating 90ZrO2 /8Ni/90ZrO2 /22Cu/5Ni/35ZrO2 has surface resistance of 2…3 ohms/square per square and light transmittance of about 60 %. These values have been obtained without heating of the substrate and, as a consequence, this coating may be deposited on temperature-sensitive materials such as polycarbonate. Moreover, since 90ZrO2 /8Ni/90ZrO2 /22Cu/5Ni/35ZrO2 coating is a multilayer coating containing layers of pure metals that have high electric conductivity and magnetic permeability and ZrO2 layers with high dielectric permeability it has higher shielding effectiveness than ITO alloy coating. It has been demonstrated that ZrO2 – Ni – ZrO2 – Cu – Ni – ZrO2 coatings may be used for protection of display screens since they comply with the requirements of screens of information displays devices.
ОЦЕНКА НАВЕДЕННОЙ АКТИВНОСТИ В ОБЛУЧАЕМЫХ МАТЕРИАЛАХ ПРИ ИСПОЛЬЗОВАНИИ ОТРАБОТАВШЕГО ТОПЛИВА РЕАКТОРА ВВЭР-1200 В РАДИАЦИОННЫХ ТЕХНОЛОГИЯХ И ПУТИ ЕЕ ОСЛАБЛЕНИЯ
Get PDFTechnical ability to use the VVER-1200 spent nuclear fuel as a source of γ-radiation to solve radiation technology problems is substantiated. The technology area for these sources is limited to the problems which do not require large absorbed doses. EGSnrs program is used to determine the absorbed dose in irradiated materials from the spent fuel assemblies (SFA). This program is a computer code system, which forms a versatile package for simulation by Monte Carlo method the bound transfer of electrons and gamma-rays with energy above a few keV. The design of the radiation installation with the irradiator based on the SFA or composed of a number of fuel rods is proposed. The irradiator is located on the bottom of the pool and can be raised above the water level, or remain under its surface, if necessary. This layer of water plays a role of the shield and decreases neutron activation of irradiated material to a safe level. In some cases, boric acid dissolved in water allows reduction of the thickness of the water layer. Results of the evaluation of materials irradiation time and the thickness of the water shield are presented.
ИССЛЕДОВАНИЕ ПРОЦЕССА ПОЛУЧЕНИЯ ДРЕВЕСНОГО УГЛЯ ПУТЕМ ПИРОЛИЗА ПОД ДАВЛЕНИЕМ
Get PDFThe preliminary results of an experimental study of the effect of pressure on the formation of charcoal in the pyrolysis of birch chips are discribed. The experimental investigation was carried out at pressures of 0.1, 0.3, 0.5, 0.7 MPa and at heating rate of the order of 1 °C/min. The initial moisture content of the chips was 14.2 % by weight, and the dimensions – 17×8×6 mm. To investigate the effect of pressure on the pyrolysis process, a laboratory bench was designed and constructed. It was found that increasing the pressure from 0.1 to 0.7 MPa increases the yield of charcoal from 25.1 to 32.4 % by weight (relative to the dry weight of the starting material) and the carbon content from 89.1 % by weight at 0.1 MPa to 96.4 % by weight at 0.7 MPa. The calorific value of charcoal decreases from 34.86 MJ/kg at a pressure of 0.1 MPa to 30.23 MJ/kg at a pressure of 0.7 MPa. This is due to release of oxygen-containing components from the porous coal structure, which have higher calorific value than pure carbon. Reduction of charcoal heat combustion with decrease in the amount of oxygencontaining components confirms conclusion that their calorific value exceeds the calorific value of pure carbon
ОЦЕНКА НАДЕЖНОСТИ ПРОИЗВОДСТВЕННЫХ ОПЕРАЦИЙ ПО ТЕХНОЛОГИЧЕСКОМУ ПУТИ ОБРАБАТЫВАЮЩЕГО ИНСТРУМЕНТА
Get PDFProcesses and equipment are classified based on mutual interactions between elements of a technological system. Reliability of each type of the technological system and operated process is different due to varying complexity of the performed operations. The main properties-determining feature of the process is the interaction of the constituent element of the technological process, mainly instrument and machining object. Based on this, technological processes in the interaction zone are divided into four groups: pointed, linear, surface and volumetric. Groups of the technological processes and determination of the reliability of their operations during goods formation is described. Colligation of the technological path with component failure rate is shown. Calculations of the technological path for each group of processes are presented. Intensities and failure rates for the all groups of processes are calculated. Based on the calculations of the object technological path, evaluation of reliability of performed operations for each group of the interactions was obtained. Obtained regularity of the component failure rate during decrease of the technological path allows quantitative comparison of the manufacturing operations reliability during its designing