DSpace Зібрання: Вісник Тернопільського національного технічного університету імені Івана Пулюя, 2012 рік, том 66, № 2

Метод інтервального прогнозування водоспоживання із використанням моделі періодичної авторегресії

2011-10-15T00:00:00Z

Назва: Метод інтервального прогнозування водоспоживання із використанням моделі періодичної авторегресії Автори: Михайлович, Тарас Володимирович; Фриз, Михайло Євгенович; Mykhailovych, T.; Fryz, M. Короткий огляд (реферат): Здійснено статистичний аналіз похибок прогнозу водоспоживання на основі моделі періодичної авторегресії з метою встановлення їх ймовірнісного розподілу. Проведено верифікацію моделі водоспоживання. Встановлено некорельованість похибок прогнозу, чим підтверджено адекватність моделі водоспоживання у вигляді послідовності періодичної авторегресії. Розроблено метод інтервального прогнозування водоспоживання на основі методів непараметричної статистики.; Among the problems of water supply systems, the most significant are: zoning of water supply systems, pressure normalizing, selection of the optimal parameters for water consumption meters control. These problems can be solved by means of water consumption forecasting. The actual task is the development of water forecasting method for detection of water supply system emergency conditions: water leaks and poor service. This method must allow to estimate forecasting errors. Interval forecast is most useful in practical application. As a result they provide intervals which contain forecasting values with pre-specified probability. Conventional methods for water supply forecasting do not meet the requirements as to the stochastic and daily-cyclic nature of hourly water consumption process. This article describes new mathematical model and forecasting method, which contributes to the solution of the tasks, concerning water supply systems. The objective of this article is to show the developed method of water consumption operative interval forecasting. Hourly water consumption process has been modeled as the periodic autoregression time series, after which, forecasting errors were estimated by performing the forecasting in the known time interval. Statistical analysis of water consumption forecasting errors has been performed using periodic autoregression model. It allowed to identify probabilistic distribution of water consumption process. New model of water consumption has been verified using the Ljung-Box Q-test. Miscorrelation of water consumption errors series has been found. Thus, adequacy of the proposed water consumption model as periodic autoregression series was proved. The method of water consumption interval forecasting has been developed using the methods of nonparametric statistics. The method of water consumption interval forecasting was tested on a computer. The results of the experimental forecasting were compared with the real water consumption values for the appropriate time points. Probability of falling out of the intervals was estimated. These probability values are very close to those probability ones, specified as the input argument to the interval estimation function. Thus, the validity of this method for solving tasks of water consumption interval forecasting, has been concluded.

Математичне моделювання процесів магнітного фільтрування і регенерації та оцінка їх ефективності

2012-01-19T00:00:00Z

Назва: Математичне моделювання процесів магнітного фільтрування і регенерації та оцінка їх ефективності Автори: Гаращенко, В’ячеслав Іванович; Сафоник, Андрій Петрович; Гаращенко, Олексій В’ячеславович; Garashchenko, V.; Safonyk, A.; Garashchenko, O. Короткий огляд (реферат): Удосконалено математичну модель, що описує закономірності процесу магнітного осадження. Запропоновано методику розрахунку ефективності процесів фільтрування та регенерації. Досліджено результати, отримані при фільтруванні та регенерації у фільтрах, які функціонують за законами, прийнятими в узагальненій моделі Мінца.; The results of the investigations deal with the problem of water system purification from the contaminating admixtures. The problem is urgent in heat and nuclear engineering, chemical and metallurgical industries. Conventional methods of water systems purification from the products of corrosion, which are based on the application of filters, the filtering nozzle of which are organic and inorganic materials, are known not to provide high level of purification. The process of filtration is especially complicated while filtering high temperature water media (≈100-200ºC) and when high-depression iron admixtures are available. Numerous investigations have testified that iron admixtures (up to 70-95%) in waters of thermal station equipment possess ferromagnetic properties. The efficiency of purification is testified to be dependent on the quality of the filtering nozzles regeneration, that is, these processes are interconnected. It has been proved that for the purification of technological water systems, in which ferromagnetic admixtures are available, the method of magnetic sedimentation of admixtures in ferromagnetic filtering nozzles, which can be realized in the magnetic filters, is worthy being applied. Magnetic filters operating includes the process of admixtures sedimentation in the filtering nozzles and the nozzle regeneration. It has been testified that nozzles regeneration time affects the filtration cycle duration, that is, the period of time, during which the filter nozzle is maximally saturated by the admixtures. Basing on the experimental results data on the effect of active parameters of the magnetic purification of liquid media upon the mass exchange coefficient, mathematic model, which describes the regularities of the process of admixtures magnetic sedimentation in the magnetized ferromagnetic nozzle, has been improved. The basis of the mathematic model are regularities of the filtering process, which are similar to the theoretical approaches of he Mints mechanical filtration theory. The proposed mathematical model includes a wide range of change of the magnetized filtering nozzle length and sedimented admixtures concentration in filtering nozzle. The model takes into account such parameters: magnetic field stress, granulated filtering nozzle diameter, time of the protective action of the magnetic filter, rate of he liquid media filtering, coefficient, which is the characteristic of he mass amount of the magnetic sediment of the ferromagnetic admixture particles per time unit. Basing on the computer experiment and using the proposed mathematic model the regeneration time, during which the maximal specific density of the nozzle saturation by the admixtures was found to be reduced to 0,5; 0,4; 0,2; 0. Nomograms for determination of the operating filtration cycle of chip and ball-shaped filtering nozzle, the period of nozzle regeneration depending on the input iron concentration and purification efficiency, have been calculated and built. The rate of the water flow regeneration was found to affect sufficiently the regeneration efficiency. Thus, at the rate V=1000 m/h during 2 min the regeneration efficiency is 85% of the maximum possible efficiency. When V=500m/h under the same conditions, the regeneration efficiency is.

Методика визначення струму, що протікає в індукторі нагрівального приладу

2012-04-24T00:00:00Z

Назва: Методика визначення струму, що протікає в індукторі нагрівального приладу Автори: Шаблій, Олег Миколайович; Пулька, Чеслав Вікторович; Базар, Мар’ян Степанович; Король, Олег Іванович; Shabliy, O.; Pulka, Ch.; Basar, M.; Korol, O. Короткий огляд (реферат): Розроблено нові індукційні енергозберігаючі нагрівальні прилади, які складаються з двох теплообмінників (внутрішнього та зовнішнього), а також електричного індуктора, приєднаного до мережі змінного струму. Визначено зведені струми, що індукуються у зовнішньому та внутрішньому теплообмінниках. Розроблено схему заміщення індуктора з урахуванням навантаження від двох теплообмінників, а також враховано власний імпеданс індуктора. Проаналізовано можливість використання схеми заміщення індуктора для системи з одним теплообмінником (внутрішнім або зовнішнім). Також визначено повний струм, що протікає в індукторі, наведено вирази для обчислення його активної та реактивної складових.; Different gas and electric devices which consume sufficient resourse ( electricity and gas) becauce of their low efficiency are used now in engineering and construction for heating of buildings and other dwelling houses. Electric devices using induction heating have found wide application lately. Usage of electric energy for heating of buildings and other dwelling houses are analysed in the paper. The lalest investigations in the field of induction heating devices are analysed. New induction energy-saving heating devisel, which consist of two heat exchangers (internal and external) and the electric inductor, connected to the ac source, have been developed by the authors. Reduced currents induced in the internal and external heat exchangers have been found. The scheme of the inductor substitution taking into account the loading from two heat exchangers and the inductor own impedance, has been developed. Besides, the complete current which flows in the inductor has been found. Expressions for calculation of its active and reactive component are presented. Saving of energy resources and looking for the alternative sources and methods of producing energy and their mutual transformation is the most urgent and competitive problem in modern world economy. Natural resources of fossil, fuels gas and oil, are coming to an end, but the pace of their consumption is increasing. Electric heating systems are the promising direction of the development of the heat power engineering of Ukraine. This is the path towards the energy security and independence from the scarce fossil fuels resources. The problem of ecological safety is urgent in the world. Thus, electrical heating systems are the leaders, even when compared with those running on the biofuels, as the electrical devices do not produce any gases and the electrical energy can be produced by transformation of the wind and solar energy and by other eco-friendly methods. Besides, Ukraine produces enough energy. Modern electric heaters consume much electricity and as compared with the gas heating systems they are more expensive with low durability, TEN-type in particular, in which pipe-type electric heaters can not operate because of heating deposit. Taking into account everything mentioned, as well as the situation we happened to be, it is necessary to develop new electric devices, which would be more efficient and durable than conventional ones. It should be noted that while developing the device, the authors took advantage of fundamental laws of physics. The solutions were built on the basis of the Maxwell equations, the law of complete current, the Joule-Lenz law, the Kirchhoff’s rules and the Ohm’s law. Only the method for finding the current force in the inductor, which is the main power characteristic of the designed device, has been analyzed in the paper, because due to the current force the efficiency of the heating device can be found. Besides, the temperature of the heat carrier will depend on the current force.

Кластерна модель комп’ютерної візуалізації мережі сенсорів

2012-04-10T00:00:00Z

Назва: Кластерна модель комп’ютерної візуалізації мережі сенсорів Автори: Демчишин, Омелян Іванович; Demchyshyn, O. Короткий огляд (реферат): З використанням методу Делоне розроблено кластерну модель комп’ютерної візуалізації бездротової мережі сенсорів, на яких можливим є здійснення атак із подальшим їх підсиленням чи послабленням сигналу. Така модель дозволяє сформувати в конфігураційному двовимірному евклідовому просторі комп’ютера геометричну структуру у формі шестикутника, яка складається із обвідки внутрішнього шестикутника правильними трикутниками, вершинами яких є сигнальні точки, а сторонами – функціональні зв’язки між сигнальними точками.; Using Delaunay method and methods of the fracture structure plotting the claster model of the computer visualization of the wireless sensor net has been developed. Such model allows constructing geometric hexagonal structure on the configuration 2D Euclid space, which consists of the regular triangle outlines, of the internal hexagonal, the vertex of which are points and the sides are the functional connection between signal points. She claster, built up in such a way, consists of 18 signal points, which are connected between each other by 36 functional connections of the same length. Signal points in the claster are connected with other points by not less than three functional connections. It allows obtaining information from each of them and visualizes the sensor operation failure. To provide visual computer interpretation of the possible attacks on the sensor, the images of which in the configuration space are signal points from different classes of their fracture, the properties of four-point com-plex are used, the possibility to find the square of its volume in particular, using Keli-Menger determinant, the elements of which are the squares of the six distances between four-point of simplex. This index for simplexes, which are expressed by the flat geometric shapes, will equal 0. Four-point triangle pyramid shaped simplex will be found by the Keli-Menger determinant, which is different from zero. Attacks on sensors cause the claster symmetry failure, which results in creation of the four-point sim-plexes in the form of three geometric shapes: simplexes, which are not connected directly which the functional connections, which define the level of the attack on the sensor in the configuration space being of the plate rhomb shape; simplexes, which have two functional connections, which change their length during the attack on the sensor, transforming into the quadrangle, the shape of which can be presented by neither a rhomb nor a quadrangle; simplexes with three functional connections, the change of length of which is caused by the attack on the sensor and are transformed into the triangle pyramid. Thus, the attack on the sensor causes: firstly geometric shape of the main part of the simplex, which fill the claster and their edges are not changed functional connections, is unchanged; secondly, transformation of two sensors with two changed functional connections into quadrangle figure of 2D configuration space; thirdly, local deflection of the configuration space to the 3D with the epicenter in the signal point, which is treated as the attacked sensor resulted from the transformation from one to three simplexes into the 3D triangle pyramid. Under such deflection of the configuration space the high of the triangle pyramid, beside the accepted in-to computer the noise signal parameters and the sensor, will define the attacked signal parameters as well. That is why local deflection of the configuration space makes it possible to find the attacked sensor, and the analytical definition of the high – to valuate the attack value on the sensor.

Оцінка граничної точності високовольтних джерел струмових сигналів на базі моделі, побудованої за їх паспортними даними

2012-04-18T00:00:00Z

Назва: Оцінка граничної точності високовольтних джерел струмових сигналів на базі моделі, побудованої за їх паспортними даними Автори: Євтух, Петро Сильвестрович; Бабюк, Сергій Миколайович; Кислиця, Тетяна Анатоліївна; Yevtukh, P.; Babyuk, S.; Kyslytsya, T. Короткий огляд (реферат): Подано матеріал, який доводить, що після компенсації систематичних складових похибки високовольтних джерел сигналів струму похибка представленої інформації знизиться приблизно в 5 разів також. Визначено границю зниження похибки, яка досягається після компенсації систематичної складової похибки. Ця величина обмежується можливостями метрологічного забезпечення на заводі-виробнику і являє собою похибку порядку 0,05%.; The role and significance of electrical energy losses in tariff setting and energy system development is evident from the fact that in the electrical energy transmission the cost of the losses is sufficient (30-40%). During the last decades the losses of electric power in the networks of Ukraine were relatively stable and equaled about 10% of the supplied electricity. However, due to different reasons in recent years they grew up to 16%. Availability of errors caused by current signals sources, leads to the significant differences of the measured electrical value, such as active power and electric energy from their real values in the high-voltage power networks. Reduction of these errors makes it possible to increase the measurement accuracy, which in its turn will result in more precise specification of bills for the consumed electricity, its quality, electricity losses in networks and to control more precisely the generators power at the power stations, which is of great importance within the energy market. Error reduction of current measuring transformers is obtained by taking into consideration its metrology properties. Until now the errors of measuring transformers were estimated by their type of accuracy, which happened to be only the characteristic of networks. Application of the additional results on the initial and finished tests of each of transformers, that is represented in a specification, makes possible to decrease these limits. It is known that the random component of measurement error can not be excluded from the results of this single measurement. The value of this random component is the exceptional theoretical limit, which can improve measurement accuracy. It was proved that the characteristics of signals of current measuring transformer can be found from the low-voltage side that allows to find these characteristics in the production conditions. The method was developed and the scheme for measuring of signals characteristics of the current transformers from the low-voltage side, that can be applied in the production conditions for finding of error similar to real under real loading was presented. It is known also, that the most traditional is the systematic error compensation which can be carried out automatically by means of computer during its operation. But up to now it was not known what is the limit of possibility to carry out compensation of the systematic component of the error in the high-voltage sources of current sources. Information, which proves that after compensation of the systematic error components of high-voltage current sources, the error of the presented information will go down approximately in 5 times . The limit of the error decrease that is achieved after compensation of the systematic error component was found too. This value is limited by the possibilities of the metrology at the plant producer and equals about 0,05%.

Elliptic curve points calculation method with the Rademacher–Krestenson’s bases

2012-02-15T00:00:00Z

Назва: Elliptic curve points calculation method with the Rademacher–Krestenson’s bases Автори: Litawa, G.; Літава, Ґ. Короткий огляд (реферат): The method of calculation for increasing the speed of performance of the basic operation on the elliptic curves, has been proposed. Calculation models using the Rademacher- Krestenson’s bases of specially selected points on the elliptic curves, have been presented. The concept of functioning of elliptic curve GF(P) points adder is based on the calculations realized within the Krestenson’s bases and parallel summing. FPGA (valve matrix programmed by the user) for the performance of operstions on the elliptic curves the Krestenson’s bases and their testing, has been presented.; Запропоновано метод збільшення швидкості виконання основних операцій в еліптичних кривих. Наведено моделі обчислень із використанням базису Радемахера-Крестенсона спеціально підібраних точок на еліптичних кривих. Концепція функціонування суматора точок еліптичної кривої GF(p) ґрунтується на обчисленнях, які реалізуються в базисі Крестенсона і паралельним сумуванням. Також представлено ПКВМ (програмована користувачем вентильна матриця) для виконання операцій на еліптичних кривих із використанням базису Крестенсона та висвітлено його тестування.

Автоматизована система релейного захисту від замикань на землю

2012-02-14T00:00:00Z

Назва: Автоматизована система релейного захисту від замикань на землю Автори: Оробчук, Богдан Ярославович; Сисак, Іван Михайлович; Бабюк, Сергій Миколайович; Orobchuk, B.; Sysak, I.; Babyuk, S. Короткий огляд (реферат): Наведено алгоритм, що використовує значення амплітуди вектора початкового нульового струму приєднання з пошкодженням і кута між цим вектором і вектором міжфазної напруги для відомого режиму розподільної мережі. Він дозволяє однозначно визначати відстань до місця пошкодження ізоляції і значення опору цього пошкодження.; The algorithm which uses the value of the damaged connection initial zero current vector amplitude and the angle between this vector and the vector of the interphase voltage for the given mode of distribution network is given in the article. It allows to find the distance to the place of the isolation damage and the value of this damage resistance. The most typical type of damages in these networks are monophase ground faults which result in the isolation break down in its weakened places. Similar damages are caused by the isolation ageing, that is why the problem of providing efficient continuous control of the isolation, its detection in proper time and trouble clearing is still very actual. The purpose of our work is to improve the method of finding the distance to the place of the local isolation damage and this damage resistance in the distribution networks, which would allow to find not only the distance to the ground faults, but to the local isolation damages, as well as to find the resistance of the isolation local damage. It is possible due to the determination of the initial zero currents vector amplitude and the angle between the vector of this current and the vector of the interphase voltage. Experimental data are compared with those obtained on the mathematic model of the network while calculating step-by-step change of the place of the predictable isolation damage along the damaged connection and the change on each step the value of resistance in the place of the isolation damage from a zero to the maximum possible. Automatic system controls continuously the amplitude of the initial zero currents of all connections. Exceeding of the given value in one of the connections is treated as appearance of the isolation damage, being a ground fault in particular. As a result according to the change of place and the damage resistanse value, the cyclic process of finding the mathematic model parameters, which are equal to those of displacement of the predicted place of the isolation damage, starts. Besides, in every stage of calculation the cycle of the predicted damage value change from zero to the maximum possible is carried out. The calculated results of the initial zero current vector in every step is compared with the actual vector of the initial zero current of the damaged connection. When the actual and calculated vectors of the initial zero current coincide, calculated values are provided in the distance, which were used in this step of calculation. The change of the network configuration is taken into mathematical model automatically while including and excluding of the corresponding element of the network. To simplify the external connections of the system hand-operated correction of the network model under change of its configuration is used. Initial zero currents phase is found according to the relation to the vector of the interphase voltage. This voltage vector does not change the amplitude, when the isolation damages of different size of the transition resistance up to the ground faults, appear. Besides, the change of phases between the vector of voltage and the initial zero currents practically does not depend on the place and the size of the isolation damage.

Класифікація атак на бездротові сенсорні мережі і шляхи їх візуалізації

2012-02-13T00:00:00Z

Назва: Класифікація атак на бездротові сенсорні мережі і шляхи їх візуалізації Автори: Чиж, Віталій Михайлович; Карпінський, Микола Петрович; Балабан, Степан Миколайович; Chyzh, V.; Karpinski, M.; Balaban, S. Короткий огляд (реферат): Проведено аналіз можливих фізичних та інтелектуальних атак, представлено систему класифікації атак на бездротові сенсорні мережі, виділено характерні особливості окремих видів таких атак. Запропоновано методи візуалізації об’ємних бездротових сенсорних мереж і окремих видів фізичних та інтелектуальних атак на них.; Classification of wireless sensor networks (WSN) according to the difference of sensors placement levels and radius of their action was interpreted. To classify WSN according to their structure a network of fire protection was used, which has sensors placed under strict rules in real residential areas. Thus, the network is a classical surface WSN. The network of fire protection is built on a multistoried building and is a conventional Volume WSN. Peculiarities of construction of a scheme of mutual relations between the neighboring sensors should take into account the mutual influence of horizontal layers of the network. WSN have a number of essential advantages over their wired analogues. But at the same time they are characterized by certain disadvantages, such as possibility of being attacked. Efficiency and reliability of the WSN functioning depends on prediction and effectiveness of control methods, of such attacks. In developing and evaluating the effectiveness of methods to withstand the attacks on WSN it is recommended to use a system of attacks classification. The system of classification of attacks on WSN was developed. Sensors, signals that are broadcasted in the network as well as confidential information may be subjected to the outside influence. That is why the attacks are divided into physical and intellectual. Physical attacks include mechanical and radio technical ones. The given classification of mechanical attacks makes it possible to facilitate the choice of method of visualization of attack area distribution and parameters of its calculation. Thus, for the visualization of a plain attack two characteristic linear dimensions which characterize the corresponding plane are used. Radio technical attacks involve destruction of an electromagnetic signal. For visualization of such attacks the measuring of a received signal power level is used. In this case the reduction in signal strength is considered as the result of increasing the distance between sensors and thus increasing the area of WSN. Intellectual or logical attacks are divided into functional and confidential. The functionality of WSN corresponds to the correct operation of all sensors in a network, routing and physical level. Thus, functional attacks are aimed at the destruction of the functional parameters of WSN. These attacks hamper basic sensor to receive complete and correct information from sensors of the lower level. Confidential attacks are divided into traffic analysis information, eavesdropping and manipulation of information routing. Typically, as a result of these attacks the attacker is able to decrypt the information, determine the route and frequency of information transfer with the aim of further organization of functional attacks on WSN. For the visualization of these attacks famous Delaunay methods of triangulation and Voronoi decomposition are used. The visualization of attacks on WSN is of primary importance. The scheme of plane attacks dissemination in the area of VWSN coverage, scheme of spherical attack distribution in the area of VWSN coverage, scheme of cylinder attack distribution in the area of VWSN coverage have been presented.

Методики відображення внутрішньої структури віртуальних організацій у грід-інфраструктурах

2012-02-15T00:00:00Z

Назва: Методики відображення внутрішньої структури віртуальних організацій у грід-інфраструктурах Автори: Сальніков, Андрій Олександрович; Корнелюк, Олександр Іванович; Бойко, Юрій Володимирович; Salnikov, A.; Kornelyuk, A.; Boyko, Yu. Короткий огляд (реферат): Проведено аналіз особливостей внутрішньої структури віртуальних організацій (ВО) та показано їх вплив на ефективне планування ресурсів провайдером грід-інфраструктури. Досліджено методи виділення ресурсів Nordugrid ARC та сформовано методики розмежування доступу за параметрами участі у ВО. Відповідно до методик розроблено програмне забезпечення, яке успішно впроваджено на трьох кластерах українського національного грід (УНГ).; Virtual Organizations (VOs) have an internal structure that was not driven by grid-infrastructure. The structure of the VO is influenced by many factors including number of members, resource usage, grid services usage and moreover social cooperation of researchers. Similarly to ordinary organizations that are usually divided into departments, hierarchical structure is also defined for the VOs. Generally, three parameters are used to describe VO structure: groups, roles and attributes. Grid-infrastructure resource provider's scheduler efficiency relies on VO internal structure recognition. Internal structure development process starts with VO particularity analysis. Virtual laboratory MolDynGrid that was established to conduct researches in structural biology and bioinformatics has been chosen as an example to demonstrate such analysis. Different requirements for several laboratory researches (molecular dynamics simulations using GROMACS software, molecular structure modeling using Modeller software, docking using AutoDock software) were described. Production versus testing computation properties were discussed. Based on performed analysis an internal structure for MolDynGrid VO has been settled. Methods of resource allocation employed by Nordugrid ARC were investigated. Necessity of binding different tasks to distinct queues of local resource management system has been shown. Lack of mechanisms for VO internal structure mapping to scheduler queues was pointed out. Analysis of the job processing algorithm in Nordugrid ARC computing element (A-REX) has shown that per-queue access control based on VO internal structure defined via Virtual Organization Membership Service (VOMS) attributes can be implemented as plug-in called out of A-REX when job gets moved to ACCEPTED state. Access separation algorithm has been developed and implemented in software. Plug-in introduces additional configuration options in Nordugrid ARC common configuration file that allow to specify access policy in terms of Fully Qualified Attribute Names (FQAN) representing internal structure developed for a VO. Software implementation of the methods presented has been successfully deployed on three Ukrainian National Grid clusters: Institute of Molecular Biology and Genetics NAS of Ukraine, Taras Shevchenko National University of Kyiv, National Scientific Centre for Medical and Biotechnical Research at the Presidium of NAS of Ukraine. Example of plug-in configuration considering particularities of Institute of Molecular Biology and Genetics NAS of Ukraine cluster has been shown. Methods are applicable to the other grid-enabled clusters.

Дослідження узагальненого перетворювача іммітансу на польовому транзисторі при зміні полярності напруги на затворі

2011-12-26T00:00:00Z

Назва: Дослідження узагальненого перетворювача іммітансу на польовому транзисторі при зміні полярності напруги на затворі Автори: Ліщинська, Людмила Броніславівна; Барабан, Марія Володимирівна; Філинюк, Микола Анатолійович; Lischynska, L.; Baraban, M.; Filinyuk, N. Короткий огляд (реферат): Досліджено узагальнений перетворювач іммітансу на польовому транзисторі при позитивній та негативній полярності напруги на затворі від індуктивного іммітансу навантаження.; Generalized immittance converter (GIC) on field-effect transistor with a p-n-junction (JFET) and with positive and negative polarity voltage on the gate of inductive immittance load was studied. JFET is included in the scheme with common source. Physical equivalent circuit JFET at different voltage polarity on the gate was interpritated. Dependences of the input resistance of the load resistance at various gate voltage polarity was investigated. The diagrams of Volpert-Smit were built. The conditions under which JFET can be used as a converter and inverter of immittance without changing the connection circuit were specified. With the negative polarity of voltage on the gate JFET possesses properties of immittance inverter, with a positive polarity of voltage on the gate JFET possesses properties of immittance converter. In general, the structures of JFET with p-n junction is similar to the structures of UJT and IST, which allows in certain modes to describe it by the similar physical small-signal equivalent circuits. The main difference is in the length and resistance of the channel (base), which significantly affects the nature of the physical processes in it. Using the JFET in direct displacement of p-n junction it is necessary to describe the T-shaped equivalent circuit which is used for the bipolar transistor, the realized GIC possessing properties of immittance converter. Application of JFET as a converter or inverter of immittance without changing of the connection circuit is limited by the quantity of the immittance transformation and relative frequency Ω.

Оцінювання точності обчислювальної процедури розрахунку параметрів теплового поля при обмеженій точності вхідних даних

2012-04-16T00:00:00Z

Назва: Оцінювання точності обчислювальної процедури розрахунку параметрів теплового поля при обмеженій точності вхідних даних Автори: Євтух, Петро Сильвестрович; Ткачук, Роман Андрійович; Липницький, Володимир Володимирович; Evtukh, P.; Tkachuk, R.; Lypnytskyy, V. Короткий огляд (реферат): Розрахунок теплових полів з допомогою сучасних обчислювальних засобів часто зводиться до розв’язку систем лінійних рівнянь, вхідні дані яких є сигналами первинних датчиків і відомі з обмеженою точністю. Викладений підхід дає об’єктивні кількісні межі, в яких від обчислювальної процедури можна домогтися необхідної точності, і вказує шлях, яким потрібно до цього наближатися. Розрахунок із застосуванням комп’ютерних методів у цьому випадку може бути неоднозначним. Тому з безлічі обчислювальних процедур необхідно вибрати таку, яка забезпечує необхідну точність розрахунку. Для підвищення точності результатів розрахунку теплових полів необхідною умовою є вибір оптимального порядку матриці, коли ще не порушена просторова деталізація поля, забезпечена необхідна роздільна здатність і досягнута висока інформативність вимірювальної системи. Щоб підтвердити необхідну точність і забезпечити єдину методику використання вибраної обчислювальної процедури, необхідно розробити процедуру її оцінювання.; The сalculation of thermal fields with the help of modern computing facilities often deal only with the solving systems of linear equations, input signals of which are the primary sensors meters and are known for their limited accuracy. The approach enables to mark objective quantitative limits within which computational procedures can achieve the required accuracy. The application of analytical expressions for the evaluation of thermal field, calculation by the computer methods of parameters in this case can be different. Since the transformation was carried out by real environments and are not isometric, that is for real environments the necessary conditions are not fulfilled. Violation of these conditions is caused by different loss of information during its passage through the environment – this is dispersion selection, incomplete aperture of the data collection, uncontrolled changes in the operator environment, obstacles in transforming of data, distortion of information, etc. Output error values of measuring of converters can be significantly increase directly by the information-measuring system. To evaluate the efficiency of the system operation it is necessary to calculate this impact on its accuracy and informative character especially when sufficient input data are not available. The paper presents the method of approach to data processing and evaluation of the measurement experiment while calculating the network losses of heat in a limited number and accuracy of input data. If the computational procedure does not provide the required accuracy, the right part in the system of equations must be changed which, practically, means to correct the measurement experiment, which requires additional resources (change of sensors and their spatial location, improvement of the measurement accuracy, etc.). This approach allows to provide optimization of the selected computational procedure and to minimize the resources to find the losses in the heating network of the city.

Дослідження еволюційної динаміки та статистичне моделювання комп’ютерних мереж

2012-03-26T00:00:00Z

Назва: Дослідження еволюційної динаміки та статистичне моделювання комп’ютерних мереж Автори: Пасічник, Володимир Володимирович; Іванущак, Наталія Михайлівна; Pasichnyk, V.; Ivanuschak, N. Короткий огляд (реферат): Розглянуто модель і сформульовано правила структурування складних комп’ютерних мереж із використанням апарата теорії графів. Роботу алгоритму моделювання, адекватність опису моделлю реальної структури проілюстровано шляхом генерації стохастичного графа з використанням статистичних характеристик реальних комп’ютерних мереж. Запропоновані алгоритми моделювання можуть бути використані для розв’язання задачі про стійкість безмасштабних комп’ютерних мереж до спрямованих хакерських атак і розповсюдження комп’ютерних вірусів у них.; The object of research carried out in this work is computer systems, the processes of evolutionary dynamics of which are described on the basis of the concept of statistical physics of complex networks. Their topology, structure, hierarchical organization, and the local properties were studied. Computer networks are not static, they evolve in space and that is why for the understanding of the dynamics of their development it is necessary to know the principles of their evolution. From this point of view, the methods were used and the choice of new algorithms for modeling of growth and structure of computer networks were interpreted. The model was considered and the rules of structuring of complex computer networks using the apparatus of graph theory were formulated. The algorithm of modeling, the adequacy of description of the real structure by the model is illustrated by the generation of stochastic graph using the statistical characteristics of real computer network, such as “BW-Star & FoxNet” and “DSS-Group” in Chernivtsi and “Avenue” in Sumy. On the basis of the empirical data and the original method of network generation for the detected law of the network nodes degree distribution modeling in the environment «Processing» were carried out, comparative analysis and systematization of the main characteristics were made. There was analyzed the influence of the statistical characteristics of networks on the structure and properties of stochastic graph models which represent them. Our estimations, modeling algorithms and the validity of applying mathematical tools allow to make a conclusion on the accuracy and adequacy of the proposed model to the real structures. The proposed algorithms of modeling can be used to solve the problem of the stability of scale-free computer networks against the directed hacker attacks and the distribution of computer viruses.

Новий підхід до формалізації процесу самоорганізації на основі теорії Рамсея

2012-04-25T00:00:00Z

Назва: Новий підхід до формалізації процесу самоорганізації на основі теорії Рамсея Автори: Крамар, Володимир Ігорович; Лупенко, Сергій Анатолійович; Kramar, V.; Lupenko, S. Короткий огляд (реферат): Запропоновано новий підхід до формалізації процесу самоорганізації на основі теорії Рамсея. Розроблено нову концепцію, що лежить в основі формалізації процесу самоорганізації. Представлено узагальнену схему процесу самоорганізації. Перевагою такої концепції самоорганізації над відомими є встановлення конкретних причин процесу самоорганізації у вигляді внутрішніх правил системи як таких, що відіграють центральну роль у самозародженні структур. Обґрунтовано використання чисел Рамсея з правилами як індикаторів процесу самоорганізації. Розглянуто обмеження використання запропонованого підходу та можливість його практичного застосування.; At present there is a wide range of mathematically formal approaches to the description of self-organizing systems, each with its advantages and disadvantages, since a unified mathematical theory of self-organization is not built. A key problem in the theory of self-organization is the investigation and establishing of regularities of spontaneous appearance of the ordered structures in systems. Up to now a lot of mathematical models which describe the self-organization in a definite way have been developed. But it is necessary to specify that most of these models have been developed for the other purposes than modeling of the self-organization process. They describe only those aspects of self-organization that are important in terms of specific applied problems. A new approach to formalization of the self-organization process based on the Ramsey theory, which studies the availability of regular structures in random configurations of elements has been proposed. A new concept that underlies in the base of the formalization of self-organization is developed. The generalized scheme of self-organization is presented. The advantage of this concept of self-organization is the determination of specific reasons for self-organization process in the form of internal system rules which play a profound role in self-creation of spontaneous structures. The usage of the Ramsey numbers with rules as the indicators of the self-organization process is interpreted. Limitations on the proposed approach and the possibility of its practical application are considered. This approach enables to interpret mathematically why the structure in the system appears and whether there are some rules which cause the self-organization.

Дослідження структури Fe–Ti, утвореної методом СВС

2012-06-05T00:00:00Z

Назва: Дослідження структури Fe–Ti, утвореної методом СВС Автори: Самчук, Людмила Михайлівна; Samchuk, L. Короткий огляд (реферат): Розглянуто механізм спікання порошків титану, вуглецю та сталі ШХ15. Розглянуто основні закономірності, при яких відбувається СВС-процес. Показано, що характерною особливістю СВС-процесу є наявність двох продуктів реакції – тугоплавкого з’єднання і окису металу-відновника. Структура такого матеріалу залежить від багатьох факторів розчинності, відношення питомої ваги, розміру реакційної маси, тиску газу. Визначено оптимальний шихтовий склад сполук з використанням порошків титану, вуглецю, сталі ШХ15. Досліджено, що для системи титан-вуглець-сталь ШХ5 синтез здійснюється в інтервалі температур від 557–1677К з утворенням інтерметалідів FeTi, Fe2Ti. В інтервалі від 1083–1677К процес відбувається інтенсивніше, при цьому утворюється інтерметалід заліза. Як показали дослідження пористість отриманої структури становить 30%. Для підтвердження структури, яка визначена металографічним методом, додатково проводили рентгеноструктурний аналіз. На термограмі видно піки термоефектів, які відповідають поліморфним перетворенням та інтенсивній взаємодії між компонентами.; The mechanism of titanium, carbon and BBS15 steel powders sintering was considered. The powder of BBS15 steel is taken in such amount which allows to link titanium and carbon completely in chemically neutral compositions. The mixing lasts eight hours to form the homogeneous mass. The synthesis is carried out in the laboratory reactor. Basic regularities under which SHS-process takes place are analysed. It is shown that the characteristic feature of SHS- process is the availability of two products of reaction - refractory connection and metal-repairer oxide. The structure of such material depends on many factors: solubility, relation of the specific weight, reaction mass amount, gas pressure. Dynamics and structure-forming mechanism of the finished goods are not studied enough. The most important is the information on the change of the forming material microstructure in the SHS waves (distribution of the grains and pores according to their sizes). Manufacturing of the ШХ15 steel powder materials by the SVS method was carried out according to the scheme: mixing of the initial reagents powders due to the stochiometric calculation according to the certain reaction equations; drying of the reagent initial charge under protection environment conditions; pressing of the reagent initial charge in the cylinder blanks of different diameter and height at variation of the material density values of the obtained samples while changing the pressing pressure; realization of the SHS-process in the laboratory device and obtaining of the functional materials samples. The objective of the paper is to investigate the structure and the chemical composition of the materials obtained by the SHS method using powders of BBS15 (ШХ15) steel. The optional charge composition of compounds was found using the titanium, carbon powders, and ШХ15 steel. It was investigated that for the titanium – carbon – ШХ15 steel system the synthesis is carried out within the temperature interval 557–1677К with the formation of FeTi, Fe2Ti intermetallides. It was found that within the interval 1083–1677К the process is more intensive, the intermetallide being formed. As the investigations testified the porosity of the obtained structure is 30%. From the technological point of view this process can be divided into such stages: initiation of burning reaction, phase-forming, cooling of the reaction products. Only those processes were investigated, which take place in the stationary mode, that is, when the burning temperature is higher than that of the product melting, because the carbon takes place in the synthesis reactions, which causes additional heat release. To confirm the structure, which was found by the metallographic method, additional X-ray structural analysis was carried out. The picks of thermoeffects are seen on the thermogram, which are similar to polymorphic transformations and intensive interrelation between the components. One of the efficient ways of decreasing the cost price of parts manufacturing is recycling of wastes of the industrial production. It was proved that in order to obtain materials in the developed installation the wastes of the machine-building industry are worth being recycled, decreasing of the energy consumption is obtained due to SHS-processes. Refractory compounds materials will possess high strength and hardness.

Оцінювання інерційних навантажень вітроколеса

2012-02-08T00:00:00Z

Назва: Оцінювання інерційних навантажень вітроколеса Автори: Корендій, Віталій Михайлович; Korendiy, V. Короткий огляд (реферат): Подано математичний опис, побудовано та проаналізовано графічні часові залежності інерційних (відцентрових, дотичних, коріолісових) навантажень, які діють на лопаті вітроколеса при їх нерівномірному обертанні навколо трьох осей: башти (при зміні напрямку вітру), вітроколеса (внаслідок взаємодії з повітряним потоком) та власних поздовжніх осей (внаслідок зміни швидкості вітру або навантаження на валу вітроколеса при використанні в якості регулятора потужності вітроустановки механізму повороту лопатей).; Two basic modes of wind turbine functioning (inconstant and permanent) are considered. The first one is limited in time (starting of the wind-wheel, connection with the electrical supply network, normal or emergency stop). In the permanent mode the wind turbine can work perfectly during long time. The inconstant modes are rather dangerous from the viewpoint of dynamics. The starting mode includes: the blade turning from the feathering to optimal position in order to support maximal power takeoff from the wind flow; the change of nacelle position after the wind direction in order to support the perpendicularity of the wind direction to the plane of the wind-wheel rotation; the change of the wind-wheel angular velocity to its nominal value. The situation, when the extreme gust of wind coincides with the change of its velocity, may arise during the functioning of the wind turbine. Also the cyclic character of inertial loading should be taken into consideration when designing the wind turbine. The resonance (the effect of sudden increase of the amplitude of forced oscillations) may arise when the frequency of inertial loading is coming near the frequency of the blade free vibrations. That’s why the purpose of this article is to build and analyze the graphical time dependences of centrifugal, tangential and the Coriolis forces of inertia and the evaluation of their extreme values in order to substantiate the expediency of taking them into consideration when designing the wind-wheels. Mathematical description of the inertial (centrifugal, tangential, Coriolis) loadings, which operate on the wind-wheel blades at their irregular compound motion – rotation round three axes: that of the tower (at the change of wind direction), of the wind-wheel (as a result of interference with air flow) and of own longitudinal axes (as a result of change of wind speed or loading on the wind-wheel billow at the use of the blades traversing gear as the regulator of wind plant power) is presented. Kinematic scheme of the wind turbine when using the mechanism of blades turning, which consists of blade, wind-wheel, nacelle, tower and foundation, is built. Time dependences of inertial loadings in the mode of the wind-wheel starting are shown. The following conclusions were made after analyzing of the obtained results: 1) the greatest influence (about 95% from equivalent inertial loading) on the blades is caused by the inertial loading, which arises at the wind-wheel rotation. Considerably smaller influence (about 5%) is made by the Coriolis force, which arises at simultaneous rotation of the nacelle and the wind-wheel. Less than 1% from equivalent inertial loading is formed by all other centrifugal, tangential and the Coriolis forces; 2) the Coriolis forces make about 10–15% from total loading on the blade of the wind turbine, when aerodynamic forces – about 50–60%, gravitational - 15–25%, centrifugal, tangential forces of inertia and other loadings – 15–25%. That’s why the task of theoretical modeling of the Coriolis inertial forces and taking them into consideration when building the mathematical models of the blade loadings is rather up to date; 3) oscillations frequencies and amplitudes of inertial loadings abruptly increase when rising the angular velocity of wind-wheel, nacelle or blade. Herewith, these frequencies may coincide with the frequency of the blade free vibrations and the resonant modes may rise during compound motion of the system; 4) most of the inertial loadings rise only under unsettled modes of wind turbine functioning, i. e. at sharp changing of wind flow direction or speed. These modes are usually short-term, but they should be taken into consideration when designing wind-wheels to provide the of maximal operation reliability of the wind turbine.

Модель методики розрахунку залишкового ресурсу ресори за наявності тріщиноподібного дефекту

2012-04-23T00:00:00Z

Назва: Модель методики розрахунку залишкового ресурсу ресори за наявності тріщиноподібного дефекту Автори: Дубицький, Олександр Сергійович; Dubytskyi, O. Короткий огляд (реферат): Проаналізовано вплив експлуатаційних чинників на зародження втомних тріщин у кореневому листі ресори вантажного автомобіля. Показано, що саме цей фактор є визначальним для розрахунку залишкового ресурсу ресори. Запропоновано модель визначення робочого циклу вантажного автомобіля, а відтак на його основі – модель розрахунку залишкового ресурсу із застосуванням сучасних підходів механіки руйнування, яка може ефективно використовуватись експлуатаційниками.; During vehicle operation, several units experience aging of their materials under the influence of stress and environment, which results in the losses of strength and fracture toughness (material degradation). The chassis components, mainly the springs are mostly subject to the degradation process. They experience all kinds of load, the influence of aggressive environments and the temperature variations. Availability of a detected crack-like defect in the spring leaf may not always result in immediate replacement of the entire spring, since the most acceptable state of the material near the crack tip is unknown. Besides, in the field operating conditions, there are limited possibilities for such technological operation to be conducted. In such a situation it is necessary to determine the loading conditions of the spring, including its root leaf with such a defect, which, in fact, determines the remaining lifetime of the whole spring, and to calculate the residual lifetime using fracture mechanics approach. As it is seen from the literature, such method of calculation is not available. Conventional methods for evaluation of the remaining lifetime of the springs are probabilistic and applied at the stage of their design. The purpose of this work is to develop a model for calculation of residual lifetime of springs containing crack-like defects, including fatigue crack, which occurs as a result of exploiting the material of the leaves. In the paper the analysis of the influence of the operational factors on the initiation of fatigue cracks in the root leaf of the truck spring was done. It is shown that this fact is sufficient for calculating the residual lifetime of the spring. The model is developed in such a way that the functional service parameters of the load-bearing elements of truck suspension are close to their threshold values. Taking it into account, such factors as a type of pavement, maximum speed of the loaded and unloaded vehicle, and place of destination in both of these cases according to the specifications are of importance. The strongest load is sure to be applied to the truck sufficient suspension, when vehicle is moving down the road paved with stones with the maximum possible speed and to the maximum distance. For this purpose the model of truck workflow based on the conditions of its most intense operation was developed. The model which comprises modern approaches of fracture mechanics is the basis for calculation of residual lifetime of the spring. It considers the possibility of crack propagation under static and cyclic loading, low-temperature creep, and takes into account the most unfavorable service conditions for the propagation of cracks, including the handling of the dynamic life cycle. The main positions of the computational model are as follows: at first initial model is constructed, where the working cycle of the vehicle is considered with the maximum loads, irregularities of the pavement, speed of travel, distance, etc. Then the oscillating frequencies are determined for the under suspension and over suspension masses in the initial and loaded states, taking into account the above mentioned factors. Then a set of working basic service parameters are determined for the root leaves of the springs based on the time of operation. Using the approaches of linear fracture mechanics, the remaining lifetime is calculated for such leaves containing a half-disk of half-elliptic cracks detected during the in-service inspection of the vehicle. For this purpose the time for fatigue crack propagation has to be determined for cyclic loading under maximum possible level, with prior determination of its cyclic and static fracture toughness. If a durable parking of the loaded vehicle is expected, evaluation of the influence of static loading on toughness of the spring leaf to the load and the crack propagation rate under low-temperature creep conditions should be carried out.

Експериментальне вимірювання жорсткості моделі гексапода

2011-11-07T00:00:00Z

Назва: Експериментальне вимірювання жорсткості моделі гексапода Автори: Кириченко, Андрій Миколайович; Kyrychenko, A. Короткий огляд (реферат): Розроблено модель гексапода і конструкцію вимірювального стенда, запропоновано методику опрацювання результатів вимірювання, що дозволяє визначити вектор узагальненого пружного переміщення платформи гексапода при навантаженні та жорсткість, приведену до точки навантаження. Встановлено залежність приведеної жорсткості від положення рухомої платформи та координат прикладення навантаження.; The parallel machine tools stiffness is the most important as to their high accuracy and performance. The hexapods stiffness is considered in the article, as the hexapod is one of the effective machine tools for multiaxis processing. The objective is to experimentally measure the elastic deformation of hexapod platform under loading by the force, to determine the spatial stiffness depending on the position of the moving platform and loading force, to calculate the reduced stiffness at the loading point. The simplified hexapod model is developed and manufactured. The model consists of solid base and the moving platform connected to the base with six variable length struts. Each strut consists of two telescopic tubes with collet clamping device to lock its length. The struts also have the universal joints at both ends. It is possible to change the platform position and orientation arbitrarily within certain range by changing the struts length. Then the platform position can be locked by tightening the collet clamps of each strut. The stiffness of each hexapod strut is measured and its average value is calculated. The measuring bench is designed to measure the solely displacement of platform caused by the struts deformation and exclude the base deformation. With the manufactured equipment it is possible to apply the force to the platform at an arbitrary direction and angle, to simulate the load on the different height of the platform, from the top or the bottom of the platform. The force is created by the screw tensioner and measured with spring force gage dynamometer. The 6x1 spatial force vector is calculated with the force value and its position within the reference frame. The platform displacement is measured by six gages placed around the platform in the particular order. The procedure of experimental data analysis is developed to obtain the generalized spatial displacement from the indicators readings and their position around the movable platform. The 6x1 vector of spatial displacement is obtained for each load and the reduced stiffness is calculated. The relations of elastic deformations from the platform position with the reference to the base and the force position with the reference to the platform are obtained. It is found that when the distance between the loading force and the platform is increased, the longitudinal displacement of the platform center decreases, but the angular displacement increases. This testifies that the longitudinal displacement at the load point is compensated by the displacement caused by the rotation of the moving platform relatively to the center of stiffness. The measurements testified that the maximum stiffness is observed when the moving platform approaches the base. The maximum stiffness is observed when the load is applied at 0.05 to 0.1 m from the joints plane. In this case the stiffness approximately equals the strut stiffness.

Дослідження сил натягу канатів при роботі натяжних механізмів машин

2012-02-01T00:00:00Z

Назва: Дослідження сил натягу канатів при роботі натяжних механізмів машин Автори: Гевко, Богдан Матвійович; Ляшук, Олег Леонтійович; Гевко, Ігор Богданович; Колесник, Олег Анаталійович; Кучвара, Іван Миколайович; Gevko, B.; Lyashuk, О.; Gevko, І.; Kolesnuk, А.; Kuchvara, І. Короткий огляд (реферат): . Наведено конструкцію стенда для дослідження характеристик гвинтових опор при вирощуванні хмелю, винограду, натягування ліній радіо- й електропередач та інше. Виведено аналітичні залежності для визначення силових, конструктивних і технологічних параметрів натяжних лебідок машин різного службового призначення для трьох розповсюджених схем їх роботи.; A stand construction for investigating the characteristics of screw supporting structures in growing hop, grapes, mounting lines of radio and electrical transmitting and others was shown. Analytical dependencies for determining power, constructional and technological parameters of tensioning winches of machines for various official purposes with three widely spread schemes of their work are derived. Three versions of using hoisting-transporting winches were considered to provide their reliability and analytical dependencies for calculation power kinematic and constructional parameters were derived. The stand for investigating characteristics of screw supporting structures of hoisting-transporting winches was made in the form of a mainframe to which main units and devices are joined. A cylindrical reduction gearbox with a driving drum, which are fixed in a box like mainframe is mounted rigidly on the mechanism body’s top left side. A rope end is fixed rigidly to the driving drum with possible rotation and winding using a handle. Between left side of the driving drum and left pillar of the mechanism body a ratchet-wheel is mounted rigidly on a ratchet sleeve. The ratchet wheel interacts with a pawl supported by a spring to the wheel. To the left of the driving drum opposite to it on the same height a roller is mounted directing the rope’s motion. This roller is installed on the axis with a possible rotation. The value of the axial displacement of the guide roller is equal to the length of the driving drum with a possible uniform placement of the rope on it. The axis is rigidly installed on two pillars and fast fixed on the top to the body by well-known methods. Lower guide roller for the rope directing with possible regulating its position in vertical and horizontal planes is rigidly mounted on the mainframe’s bottom opposite to the guide roller by the well-known methods. A hook connecting the rope with a dynamometer for measuring tension force value on screw support is rigidly fixed further on the left along the rope. The other end of dynamometer is joined to the hook and the rope which is rigidly fixed to the screw support pin. Through a hole a screw by which the screw support is tightened into the soil is rigidly welded to the screw support. The hole of the screw support is on the minimal height over the soil level to prevent its excessive bending. A tripod signal pyramid is used to investigate the strength of screw support pin and the screw itself and also the rigidity of the weld by which the screw is fixed to the screw support. The pyramid is mounted over the screw support on the top of which a bearing roller on the axis with possible circular rotation. Besides the axis is parallel to the axis of the driving drum and is mounted on the same height. And two supports of tripod signal pyramid are placed on the top of the screw support axis for normal load receive. On the right end on the mainframe the analytic-digital transformer and computer are installed to fix the rope tension force by dynamometer while investigating both the value of force of screw support resistance and screw rigidity by well-known methods.

Деформівно-напружений стан несучої системи грейферного навантажувача ПЕА-1А

2012-02-14T00:00:00Z

Назва: Деформівно-напружений стан несучої системи грейферного навантажувача ПЕА-1А Автори: Рибак, Тимофій Іванович; Ріпецький, Євген Йосипович; Сікорський, Сергій Петрович; Rybak, Т.; Ripetskyi, Y.; Sikorskyi, S. Короткий огляд (реферат): Розглянуто плоску просторово-навантажену рамну конструкцію навантажувача-eкскаватора самохідного ПЕА-1А модифікованим методом мінімуму потенціальної енергії деформації для розв’язку задач пошукового конструювання та оптимізації геометричних параметрів несучих систем за повним напруженим станом. Отримано рекомендації для раціональнішого взаємного розміщення найбільш навантажених елементів, що призвело до підвищення їх міцності при одночасному зниженні матеріаломісткості.; Space-loaded frame structure of agricultural grab loaders and theirs components need improvements. Besides, constructional system of the grab loader tends to change from the considerable differences of rigidity. Planar space-loaded frame structure of the self-propelled excavator is analyzed in the article using the modified method based on the principle of minimum potential energy of deformation to solve the problems of design and optimization of geometrical parameters of the frame structure in complete tension. The calculation of simple frames with help of other methods is extremely bulky and takes much time, but this method simplifies even the calculation of the complicated frame structure. Metalwork of grab loader consists of longitudinal longerons with five different profiles. The main loads acting on the frame structure of grab loader are the external forces from the engine and gear-box, driving axle, speed-reducer and rear wheels, turning cylinders and boom of loader. These forces are counterbalanced by reactions of five fulcrums of the grab loader. The investigation of the stressed-strained state of frame structure of the grab loader begins with the design of the main scheme of calculation. Conditional intersection along the frame symmetry plane is used for construction of basic model of the grab loader and the action of the first part on the second is substituted by the internal unknown force factors. If the frames are composed of elements of an open section, the energy of torsional deformation is only taken into consideration that does not influence the final results. Potential energy of deformation of the frame of this type is equal to the sum of potential energies of its parts: potential energy of the first part of the frame of its elements under torsion and potential energy of the second part in the same condition of deformation. The expression of potential energy of deformation of both parts of the frame of its elements under torsion is formed on the basis of the following assumptions:  units of conjunction of traverse with longitudinal longerons are left unchanged before and after the deformation;  power of deformation of shear and distension is not taken into consideration;  the influence of moving power on distribution of internal forces in elements of frame of pull-type machines is neglected. Suitable quantity of unknown forces is excluded from the function of potential energy with the help of the equations of statics. Integrands of functions of potential energy of deformation are differentiated using the Leibniz’s rule. Definite integrals are calculated. According to the theorem on the smallest work each of derivatives of the potential energy of deformation equals to zero. As the result, a system of linear canonical equations is aggregated. Received canonical equations are divided into two independent systems for calculation of space-loaded frame structure. The first is used for the determination of symmetric and antisymmetric unknown values. It results in simplification of computation of this system. The second is used for algorithmization of calculation. As the result the internal unknown force characteristics are found. Tensity of the most dangerous section of the frame structure is determined using the numerical values of internal unknown values and predicted external loads. Recommendations for more efficient mutual locations of loaded elements are obtained the result of which is the increase of their strength while reducing material capacity.

До питання про фізичні співвідношення деформаційної теорії термопластичності

2012-06-08T00:00:00Z

Назва: До питання про фізичні співвідношення деформаційної теорії термопластичності Автори: Михайлишин, Михайло Стахович; Головатий, Богдан Зеновійович; Mykhaylyshyn, M.; Holovatyy, B. Короткий огляд (реферат): Розглянуто узагальнення деформаційної теорії термопластичності при неізотермічних процесах навантаження з урахуванням можливого пружного розвантаження після пластичного деформування, повторного пластичного деформування після пружного розвантаження і навантаження в протилежному напрямку до напрямку початкового навантаження, повернення на криву початкового деформування при навантаженні в напрямку початкового навантаження після пружного розвантаження, повторного пружного розвантаження після повторного пластичного деформування і т. д. з метою використання її для моделювання процесів зварювання тонкостінних елементів конструкцій. Отримано фізичні залежності в компонентах напружень і деформацій для довільного етапу деформування і знайдено формули для обчислення пластичних деформацій. Фізичні залежності записано у формі, яка дозволяє при реалізації обчислювальних алгоритмів використовувати метод додаткових деформацій для лінеаризації фізичної нелінійності.; Generalizations of the deformation theory of thermoplasticity under non-isothermic loading with the possible elastic unloading after plastic deformation, repeated plastic deformation after elastic unloading and loading in the direction opposite to the initial loading, return to the curve of the initial deformation under loading in the direction of initial loading after elastic unloading, repeated elastic unloading after repeated plastic deformation, etc. in order to use it for the modeling of welding of thin-walled structural elements are described in the article. Physical correlations under elastic unloading are obtained on the basis of the rule that directing stress tensors and elastic deformations coincide. Thus, the equations are obtained, which in its form are similar to those of the generalized Hooke's law, but interconnect the difference between the current stresses and tensions brought at the beginning of unloading to the temperature distribution in the body, where stress and the difference between the current deformations and deformations at the beginning of unloading are determined. The same equations can also be written in the form of the generalized Hooke's law between the current stresses and differences between the current deformations and plastic deformation at the beginning of unloading. The obtained equations are generalized in case of the repeated plastic deformation similarly to the equation of deformation thermoplasticity theory based on the thermoelasticity equations. Hereby, it is much easier for the plastic deformation description to use the dependence of , which depends only on the obtained plastic deformations at the beginning of unloading, rather than on the total deformation and temperature for this moment. It is shown that the last dependence in the elastic unloading field is to be presented favourably in different coordinate systems and the conditions that correspond to different directions of loading are indicated. Similar dependences are obtained when the repeated plastic deformation is changed by the elastic unloading with the further plastic deformation. Physical dependencies in the components of stress and deformations for any stage of deformation are obtained. Formulae for calculation of plastic deformation are found. Physical dependencies are written in the form, which allows to apply the method of additional deformations for linearization of the physical non-linearity under realization of the calculation algorithms.

Стиснення двома жорсткими кільцевими штампами ізотропного шару з наявними залишковими деформаціями

2012-06-02T00:00:00Z

Назва: Стиснення двома жорсткими кільцевими штампами ізотропного шару з наявними залишковими деформаціями Автори: Шелестовський, Борис Григорович; Габрусєва, Ірина Юріївна; Shelestovskiy, B.; Gabruseva, I. Короткий огляд (реферат): Наведено розв’язання контактної задачі про стиснення попередньо напруженого ізотропного шару двома співвісними жорсткими кільцевими штампами. Розглянуто числовий приклад та побудовано функції розподілу контактних напружень для обох ділянок контакту. Проаналізовано вплив залишкових деформацій у шарі на розподіл контактних напружень.; Increasing reliability and durability of structures and mechanisms is one of the most actual tasks of modern construction and engineering. As it is known [2], residual deformation is almost always available in the structural elements and machine parts. The nature of their appearance can be very different: irreversible deformation (plasticity, creep), structural changes in the material, changes of the aggregate state in some areas, mechanical, chemical and technological processes, etc. Resulted stress, can cause fracture and accelerate some phase transitions, corrosion. Consideration of the residual strains under development of the important structural elements of machines and installations can estimate more accurately the material strength life and significantly reduce its costs, while maintaining the necessary functional characteristics of the elements in general. That is why the study of the contact interaction of the elastic bodies with residual deformations is up to date and will remain so in the future. Research problems of the contact interaction of the preliminary stressed bodies in our country and abroad had appeared in the sufficient quantity only by the end of the last century. First of all it is due to the fact that the linear elasticity theory does not consider of residual stresses in bodies. In general, strict formulation of such problems requires the use of system of the nonlinear elasticity theory, however, for the sufficiently large values of the initial stresses its linearized version can be referred to. Current level of linearized elasticity theory and mathematical techniques, combined with the rapid development of computer technology makes it possible to form effectively a variety of computational models in a wide range of tasks. Complete enough description and classification of works devoted to the theory of contact interaction of the preliminary stressed bodies with rigid punches can be found in [1]. But the interaction of the complex configuration circular punches with the residual deformation elastic half-space and layer stays not studied enough. In the article the solution of the contact problem of compression of the preliminary stressed isotropic layer with two annular punches using the linearized theory of elasticity was built. All calculations are performed in the location of strain , which are associated with the coordinates of the initial state relations , where – coefficient of linear elongation element directed along the Cartesian axis . Using the basic relations of the linearized elasticity theory, the problem is treated as the construction of the solution of the triple integral equations with kernels involving the Bessel functions. The authors have developed a method of approximate solutions of this type. The main idea of this method is to represent the unknown distribution function of the contact stresses in the form of the Fourier series with unknown coefficients and to construct a system of the linear equations for finding them. To demonstrate the proposed methods the numerical example of the construction of the contact stresses distribution function is presented in the paper. Besides, the residual deformation field characteristics effect on the amount and nature of the contact stresses under punches has been analyzed.

Розрахунок критичного приведеного напруження зсуву для полікристалічного титану

2012-03-13T00:00:00Z

Назва: Розрахунок критичного приведеного напруження зсуву для полікристалічного титану Автори: Герасимчук, Олег Миколайович; Герасимчук, Олена Михайлівна; Herasymchuk, Oleg; Herasymchuk, Olena Короткий огляд (реферат): Запропоновано модель для розрахунку дійсних величин критичного приведеного напруження зсуву (КПНЗ) для необоротного ковзання в системах ковзання різного типу, які притаманні титановим сплавам. Показано, що різна величина КПНЗ для різних систем ковзання залежить від модуля пружнос-ті і величини вектора Бюргерса.; The onset of plastic deformation, i.e., the onset of irreversible slip of dislocations in different slip systems of certain metal crystals is determined numerically by the critical resolved shear stress (CRSS). However, in the case of polycrystals, it is impossible to determine accurately the CRSS value, since the dislocation motion is retarded by the gain boundary. For this reason, the grain size of a polycrystal affects the CRSS value. Based on this assumption, the paper presents a model for calculating the CRSS in a polycrystalline α-titanium, because titanium alloys belong to such class of materials in which the local plastic deformation due to a monotonic or cyclic loading is initiated on shear planes, most preferably located with respect to the loading direction. In hexagonal close-packed crystal structure (hcp) of α-titanium with lattice parameters a=0.295 nm and c=0.468 nm the following four types of slip systems can be activated: 1) < > in the basal plane (0002) with a slip direction  ; 2) < > in the prismatic plane { } with a slip direction  ; 3) < > in the pyramidal plane { } with a direction   and < > first order pyramidal slip in the same plane with a direction  ; 4) second order pyramidal < > slip in the plane { } with a direction  . The easiest system is the slip system with the Burgers vector in the prismatic plane. To calculate the CRSS using the proposed model, it is necessary to know the modulus of elasticity and the proportionality limit of the material, which are determined from the results of the short-term tensile tests of standard specimens. Besides, from the metallographic analysis, it is required to determine the mean linear size of the structural element (in the case of titanium alloys, this is the size of α-globules for globular and bimodal structures and the thickness of α-lamellae for lamellar structures) and the preferred direction of crystals with respect to the load direction, that is, the Schmid factor and the Burgers vector. The testing of the proposed model using the experimental results taken from the literature for single crystals of commercially pure α-titanium has shown a good coincidence between the calculated and experimental results. An error in determination of the CRSS is -3.3...+0.8%. In the paper it is also shown that for different slip planes in the hcp crystal lattice of α-titanium, the ratio of the CRSS values is determined by the ratio between elasticity moduli and the Burgers vectors for the corresponding planes. Basing on it, the ratios between the CRSS for the prismatic and basal < > slips and first order pyramidal < > slip are found. They are 1:1:2.6, respectively, i.e. they virtually coincide with the experimentally obtained by different authors for various titanium alloys. The proposed computational model can be used as express-evaluation of the characteristics of the static and fatigue strength in the development of new materials, since it enables one to obtain the value for CRSS without time-consuming and long-term experimental investigations.

Кавітаційно-ерозійна зносостійкість зміцнених поверхонь конструкційних сталей в середовищах харчових виробництв

2012-01-10T00:00:00Z

Назва: Кавітаційно-ерозійна зносостійкість зміцнених поверхонь конструкційних сталей в середовищах харчових виробництв Автори: Стечишин, Мирослав Степанович; Білецький, Олександр Олександрович; Береговий, Андрій Іванович; Мартинюк, Андрій Віталійович; Stechishin, M.; Bileckiy, O.; Beregovoy, A.; Martinyk, A. Короткий огляд (реферат): Розглянуто вплив термоциклічної обробки (ТЦО), іонного азотування і полімерних покриттів на кавітаційно-ерозійну зносостійкість конструкційних сталей. Отримані результати пояснюються фізико-механічними, електрохімічними характеристиками досліджених матеріалів з покриттями.; To improve cavitation and erosion wear-resistance of metals methods of surface strengthening must be used. For this reason the paper studies the influence of thermo-cyclic treatment (TCT), ion nitriding and polymer coatings on cavitation and erosion wear-resistance of C 45, 15Cr3 and 41 Cr 4 steels. Thermo-cyclic treatment of C 45, 15Cr3 and 41 Cr 4 steels was conducted using pendulum and medium-temperature approaches. Ion nitriding of normalized and temro-cycled samples of C 45 and 41 Cr 4 steels was conducted taking advantage of hydrogen-free nitriding machine and in a nitrogen-argon mixture at 500 and 560 оС. Coatings made of polypropylene PPR2 and fluorine plastic PTFE4 were sprayed on C 45 steel by the electrostatic method and colliquated in the furnace at the temperature 200...280 оС. The thickness of polymer coating was within 200...250 mkm. Research on cavitation and erosion wear-resistance has been done taking advantage of the magnetic strictional pulsator (MSP) in neutral, acidic and alkaline environmnet (3% NaCl, serum and milk). The results of the study have shown that TCT of structural steels improves the mechanical properties of plasticity, small-and multicyclic durability, corrosion resistance and, approximately by 35%, cavitation and erosion wear-resistance under the primary influence of corrosion damage factor. The developed technology of low temperature nitriding of structural carbon steels increases their cavitation and erosion wear-resistance in 1.15, 1.63, 1.65 and 1.84 times in the 3% aqua of sodium chloride, serum, milk and lactic acid respectively, that is by 10...32% higher compared with the conventional methods of nitriding. Polymer coating based on polypropylene and PTFE allow to increase in 2 times the cavitation and erosion wear-resistance of C 45 steel in a neutral (3% NaCl) and more than in 40 times - in acidic solutions. Especially effective is the application of polymeric coverages in a sour environment, where the increase of cavitation firmness presents more than in 40 times. Thus application of fluoroplastic for making of cavitation firmness detailsincreases their wearproofness more than in 50, and from a polypropylene – 60 times.

Дослідження напружено-деформованого стану триплексів при експлуатації в умовах знижених температур

2012-04-10T00:00:00Z

Назва: Дослідження напружено-деформованого стану триплексів при експлуатації в умовах знижених температур Автори: Мильніков, Олександр Володимирович; Підгурський, Микола Іванович; Mylnikov, О.; Pidhurskyy, M. Короткий огляд (реферат): Досліджено напружено-деформований стан (НДС), який виникає в тришарових клеєних скляних конструкціях – гомогенних та гетерогенних триплексах з обрамленням та без нього, в результаті температурних впливів на конструкцію.; Triplex glass is widely used for glassing vehicles (automobiles, railway vehicles, aircrafts and ships), windows and facades of buildings. Such constructions often work under sudden drops in temperature [extreme temperatures]. Therefore, the research of the stressed-strained state of triplexes in exploitation at low temperatures is of a great topicality The aim of the work is to research the stressed-strained state (SSS) appearing in the three-layered glued glass constructions: homogeneous and non-homogeneous triplexes with and without framing line, as a result of temperature influences. The problem has been solved with the polarized-optical method (POMM) – method of photoelastisity. The idea of modeling had been considered and implemented before analyzing SSS in full scale samples, in order to create and practice the methods of temperature load and research, as well as destruction of samples. Herewith, the same materials were chosen for triplexes models and full scale samples. Experimental conditions lied in determining the stressed-strained state (SSS) in the explored triplexes during the decrease of temperature from room T=293K to the fixed values of T = 273, 253, 233, 213 K and identifying the moment of their destruction. The method of integrating differential equations of equilibrium in finite differences has been used for the stress separation. According to the research objectives the maximum tangential (critical) stresses τmax and normal stresses σх and σу formed in the zones of glued surfaces contact have been defined. The distribution of normal stresses σх directed at each point along the gluing in triplexes, stress σу directed perpendicular to the gluing layer and tangential stresses τmax are presented graphically. The analysis of the received results has been conducted. The testing data indicates that the fracture of heterogeneous triplexes without framing line occurs at temperatures ~ 268 K, and with the frame line - at temperatures ~ 245 K. Moreover, the process of destruction takes place in the layer of silica glass in parallel with the gluing. In other samples the destruction in the researched range of temperatures was not observed. The reason for the destruction of heterogeneous structures is, evidently, the character of SSS, changing from compressive stresses at the edges of samples to stretching stresses in the middle of the sample. This situation leads to the detachment of silica glass and its destruction. The testing data can be used in glassing vehicles (automobiles, railway vehicles, aircrafts and ships), windows and facades of buildings.

Експериментальне оцінювання механічних властивостей металу трубопроводу зі сталі 17Г1С–У після тривалої експлуатації

2012-03-02T00:00:00Z

Назва: Експериментальне оцінювання механічних властивостей металу трубопроводу зі сталі 17Г1С–У після тривалої експлуатації Автори: Гопкало, Олексій Петрович; Юхимець, Петро Сергійович; Бернацький, Олександр Вікторович; Гопкало, Олена Євгенівна; Каток, Олег Анатолійович; Дмитриєнко, Роман Ігорович; Gopkalo, O.P.; Yuchsmetz, P.; Bernatsky, O.; Gopkalo, O.E.; Katok, O.; Dmitriyenko, R. Короткий огляд (реферат): Наведено результати експериментального визначення характеристик короткочасної статичної міцності та пластичності металу трубопроводу з поздовжнім заводським зварним швом. Встановлено, що характеристики міцності та пластичності основного металу трубопроводу та металу зварного шва залежать від напрямку прокату та форми лабораторних зразків. Визначення характеристик міцності металу трубопроводу неруйнівним методом інструментованого індентування добре узгоджуються з даними механічних випробувань.; The results are presented for the experimental determination of the short-term static strength and ductility of the metal in the longitudinal and transverse directions of the pipe of steel 17G1S-U with a factory-made longitudinal welded joint after a long operation. Specimen blanks were cut out of a piece of the pipe of 530 x 8 mm in diameter. The mechanical properties of the base metal (BM) and the metal in the specific areas of the welded joint: weld metal (WM) and the metal of the heat-affected zone (HAZ) were determined in the transverse direction of the pipe. The mechanical properties of the BM and WM were determined in the longitudinal direction of the pipe. The strength and plasticity characteristics of the pipe metal were determined by conventional tensile testing of laboratory specimens and a nondestructive instrumented indentation technique. For conventional tensile tests, flat specimens (with a treated and untreated test portion), both full-sized cylindrical specimens and those with a shortened test portion (for weld zones) were used. The strength characteristics of the BM were determined by a nondestructive instrumented indentation technique, whereas the strength of the specific areas of the welded joint was determined under static and cyclic loading conditions using a ball indenter of D = 2.5 mm. It is found that the mechanical treatment of both surfaces of the flat specimen of the BM increases the ultimate strength by 4.8%, the offset yield stress by 7.6% and the reduction of area by 16% as compared to the specimen with an untreated surface. The machining of the external or internal surface of the flat specimen increases the ultimate strength only by 1.2% as compared to that with an untreated surface. Tensile tests of specimens with a treated surface (flat and cylindrical specimens) of the BM and WM give a higher ultimate strength (by 6.3-7.6%) as compared to the similar data obtained for flat specimens having the BM without surface treatment, regardless of the rolling direction. The data obtained in testing of cylindrical specimens cut out in the transverse direction of the pipe and having a shortened test portion for the BM and WM exhibit higher ultimate strength and offset yield stress (by 5.46% and 2.86% and 8.7% and 9.05%) and lower reduction of area by 11.42% and 14.42% as compared to the corresponding characteristics obtained for full-sized cylindrical specimens in the longitudinal direction of the pipe. The determination of the strength characteristics of the pipeline metal by a nondestructive instrumented indentation technique agrees well with the data of conventional mechanical tests.

Визначення напруженого стану залізобетонної балки, підкріпленої поперечною арматурою

2012-02-27T00:00:00Z

Назва: Визначення напруженого стану залізобетонної балки, підкріпленої поперечною арматурою Автори: Лучко, Йосип Йосипович; Распопов, Олександр Сергійович; Добрянський, Іван Михайлович; Luchko, J.; Raspopov, O.; Dobrjanskiy, I. Короткий огляд (реферат): В роботі побудовано схему розрахунку напруженого стану залізобетонної балки, будівлі моста, підкріпленої поперечною арматурою, яка ґрунтується на розв’язку відповідної задачі теорії пружності про рівновагу полоси, до бокових граней якої прикладене дотичне зусилля, яке зрівноважує зовнішнє навантаження.Основні рівняння математичної моделі балки отримані, виходячи з умов сумісності деформації бетону й арматури та розгляду рівноваги елемента балки. Запропоновано методику побудови наближеного розв’язку одержаних рівнянь, яка базується на використанні рядів Фур’є за системою тригонометричних функцій. Отримано апроксимаційну залежність дотичних напружень в поперечному січенні армуючого шару. Проведено дослідження зміни дотичних напружень вздовж довжини і висоти балки. Отримані результати можуть бути використанні при пргнозуванні зародження та розвитку тріщин в армованих залізобетонних балках, що перебувають під дією силових навантажень.; The scheme of the stressed state of the reinforced beam, bridge structure strengthened by the lateral reinforcement, which is based on the solution of the certain problem of the elasticity theory on the strip equilibrium, to the edge sides of which shearing force is applied, which balances the external loading, has been built. Basic equations of the beam mathematic model were obtained, in the conditions of the concrete and reinforcement deformation compatibility and analyses of the beam element equilibrium. The method of finding the approximate solution of the obtained equations, which is based on the application of the Fourier series according to the system of the trigonometric functions, was proposed. Approximation dependence of the shearing stresses in the cross-section of the reinforced layer was obtained. Investigations of the shearing stresses change along the beam length and height were carried out. Obtained results can be applied for the prediction of the initiation and growth of cracks in the reinforced concrete beams which are under the power loadings.

Підвищення опору руйнуванню зразка з тріщиною внаслідок обробки імпульсним магнітним полем

2012-03-02T00:00:00Z

Назва: Підвищення опору руйнуванню зразка з тріщиною внаслідок обробки імпульсним магнітним полем Автори: Степанов, Генадій Володимирович; Харченко, Валерій Володимирович; Котляренко, Андрій Аркадійович; Мамєєв, Іван Анатолійович; Stepanov, G.; Kharchenko, V.; Kotliarenko, A.; Mameev, I. Короткий огляд (реферат): Наведено методику та результати експериментальних досліджень впливу обробки імпульсним магнітним полем (ІМП) на опір руйнуванню компактних зразків з попередньо вирощеною тріщиною втоми, виготовлених зі сталі 45. Перед обробкою ІМП зразки механічно навантажували розтягом до рівня напружень у вершині тріщини, при яких значення коефіцієнта інтенсивності напружень нижче за його критичне значення (Кс). У результаті обробки ІМП у зразку відбувається релаксація напружень за рахунок пластичної течії у вершині тріщини, що призводить до її притуплення. Результати випробувань оброблених зразків показали істотне підвищення опору руйнуванню в порівнянні зі зразками в початковому стані.; Experimental technique and results of investigations of the effect of pulsed magnetic field (PMF) treatment on fracture resistance of the fatigue pre-cracked compact tension (CT) specimens are presented. Each specimen, made out of a hot-rolled sheet of medium carbon steel 45, was cut by the electric discharge machine. The initial starter notch in the specimens, perpendicular to the direction of rolling, was performed. To avoid possible residual stresses in the specimens after their manufacturing operations annealing was used. A natural sharp fatigue crack in CT specimen was created by cyclic loading. Before PMF treatment, in order to form the initial elasto-plastic stress in the crack tip and to reduce the electrical contact between its edges, treated specimen was mechanically preloaded in tension using special pool-rods. The load was carried to the stress level in the crack tip at which the value of stress intensity factor does not exceed its value on the last step of loading at growing of a natural fatigue crack in the specimen. The pulse magnetic field was provided by discharging a bank of high voltage capacitors through connected in a transmission line circuit with inductors, installed on both sides of the specimen. The parameters of current discharge were monitored using a calibrated non-contact inductive probe, called the Rogowski coil, placed around one of the current feeding wires and recorded on a personal computer (PC) with pre-installed high-frequency analog-digital card. For all specimens the same parameters of current discharge were used. According to measurements the discharge current was about 11 kA for the total duration of 10 ms. Direct measurement of the load, applied to the specimen and temperature rise in the vicinity of fatigue crack during PMF treatment were also recorded. After treatment irreversible relaxation (significant force decreasing) and negligible increase in temperature in the vicinity of the crack were observed. After testing at room temperature CT specimens in the initial state and specimens after PMF treatment, the values of maximum stress intensity factor Kmax and strength ratio of specimen Rsc were obtained. Test results showed a substantial increase of the fracture resistance of the treated specimens in a comparison to the specimens in an initial state. Stress relaxation, caused by plastic flow in a vicinity of the crack, takes place due to PMF treatment and provokes a crack blunting. This fact was confirmed by increasing the value of a crack opening displacement of the treated specimen in comparison with its initial state. Increasing of fracture resistance should be mainly associated with blunting of the crack due to plastic flow in its tip, caused by the relaxation of initial elastic-plastic stress under electroplastic and magnetoplastic effects

Пружно-пластична задача для обмеженої пластинки з м’яким еліптичним включенням

2012-03-27T00:00:00Z

Назва: Пружно-пластична задача для обмеженої пластинки з м’яким еліптичним включенням Автори: Максимович, Володимир Миколайович; Пастернак, Ярослав Михайлович; Приходько, Олексій Сергійович; Maksymovych, V.; Pasternak, Ia.; Prykhod’ko, O. Короткий огляд (реферат): Розглянуто пружно-пластичну задачу для обмеженої пластинки із м’яким еліптичним включенням. Визначення напруженого стану проведено за допомогою методів граничних елементів та змінних параметрів. Досліджено напружено-деформований стан пластинок залежно від розміщення включення та прикладеного навантаження з урахуванням зміцнення матеріалу.; Experimentally it is found that most of the materials are more or less macroscopically inhomogeneous. In particular, structural elements contain many inclusions, which can induce crack initiation. When the stress is sufficient to deform permanently the material of a solid or an inclusion, elasto-plastic deformations should be also accounted for, because plastic deformation involves the breaking of a limited number of atomic bonds by the movement of dislocations. Thus, determination of the elasto-plastic state in the vicinity of inclusion tips is essential in the study of the plate-like structural elements strength. Similar studies were provided mainly for the truly elastic case, or for the infinite plates. However, in practice the size of inclusions are often comparable with the size of the structural element. This significantly influences stress field and stress concentration inside the inclusion and near it. This type of problems can be solved numerically; however, for complex geometry it will require high computational performance and large amount of time. On the other hand, the solution of elasto-plastic problem for a soft inclusion in the infinite plate is quite simple and is easy-to-use in the engineering applications. Therefore, it is of considerable interest to test whether the latter can be applied to the calculation of finite plates with inclusions. This paper provides the analysis of elasto-plastic state of a soft inclusion embed into a finite square plate and the stress/strain field of inclusion and a plate using the boundary element method combined with the method of variable elastic parameters. In this approach, the problem of elastic-plastic deformation of the inclusion is reduced to the solution of the sequence of linear algebraic equations for Mises stress inside the inclusion, which is obtained based on the boundary element method, in which the kernels are related to that Mises stress by constitutive relations of the method of variable elastic parameters. Based on the obtained numerical solution the elastic-plastic state of plates with inclusions of different size and placement is analyzed. Stress/strain state of the plate is studied depending on the position of inclusion and the applied load. Material hardening is accounted for. Obtained results are compared with the solutions for infinite plates under the same input data. It is found that for the inclusion, which dimensions are two or more times smaller than that of a plate, the divergence of the numerical results and the closed-form solution for infinite plate does not exceed 1%, which is quite acceptable for engineering calculations. Critical load and orientation of the inclusion are studied as well. Thus, it is found that the calculation of Mises stress inside the inclusion under relatively low loads can be provided based on the solution for infinite plates. It is also found that the nature of the stress distribution in the inclusion and the plate is different. In particular, the maximal Mises stress inside the inclusion are the greatest for tension of the plate at an angle of relatively to the bigger semi-axis of the inclusion, and in the matrix for the transverse tension.

Згин кусково-однорідної пластинки з криволінійним розрізом за умови контактування його берегів

2012-03-02T00:00:00Z

Назва: Згин кусково-однорідної пластинки з криволінійним розрізом за умови контактування його берегів Автори: Сяський, Андрій Олексійович; Музичук, Катерина Петрівна; Syasky, A.; Muzychuk, K. Короткий огляд (реферат): Побудовано систему сингулярних інтегрально-диференціальних рівнянь для задачі про згин нескінченної кусково-однорідної пластинки з криволінійним розрізом за умови контактування його берегів. Розрахунок напруженого стану здійснено числовими методами механічних квадратур і колокації.; Mixed contact problem for the piecewise homogeneous lamellar construction which contains the infinite isotropic plate with the curvilinear hole and the complete hard disk, which are partly soldered between each other on the line of delimiting, is considered. The edges of the cut between the plate and the disk are contacting along the line providing bending load in the plate which is acting on the infinity in the direction of the coordinates. As a result of it the plate is in the conditions of the generalized two-dimensional stress state and the cylindrical bending. The solving of the problem includes the determination of the components of stress state on the contour of the hole of the plate, the size and the position of the contact zone. The boundary conditions of the problem on the smooth contact zone of the plate and the disk are formulated as the equality of the normal displacements of contour points on one of the faces. Thus, it was considered that the contact stress is brought in the mean plane of the plate with the addition of the corresponding bending moment. In the zone of the soldered joint the boundary conditions of the problem are formulated as the equality of contact stresses and moments and also as the equality of the displacement vector components and the rotation angle of normal line up to the mean plane of the plate and the disk. The dependencies between the displacement vector components and the rotation angle of normal line in the plate contour points and the stresses contact are presented in the from of the integral relations with the logarithmic kernels. Their substitution in the boundary conditions leads to the system of singular integral-differential equations for the determination of the functions through which the contact stresses and the moments are determined. Finding an exact solution for this system makes great mathematical problems, so the solution is found approximately. The decision structure for this system at the contact zones and soldered joint was determined for the case of the non-full contact of cut banks. As the contact between the plate and the disk is smooth the normal stresses and the moments are limited in the contact zone and are equal to zero. At the ends of the zone of the soldered joint the contact stresses and the moments have the root feature on which the local oscillation is superposed. The numerical realization of this problem has been conducted by the methods of mechanical quadratures and the collocation by which the influence upon the size of contact zone and the shape of the hole on the stress state components allocation at the triangular contour hole of plate have been analyzed. The size and the position of the contact zone are determined by the method of dichotomy. The results of the numerical calculation of stress state components are illustrated on the graphs. At the top of the graphs was built distributions of the contact stresses and the hoop stresses and at the bottom of graphs – distributions of the contact moments, the hoop and the rotational moments were built. According to the results the size of the contact zone considerably depends on its curvature. The values of the contact zone for these examples are presented in the article. This problem is new for the formulation and the solution method. In scientific literatures there are only some published works in which by the reduction to the problem of the linear conjugation the stress state of the complete infinite isotropic plate with one or two cuts on the arc of the circle, the edges of which are contacting in the process of the flexible deformation, is researched.