Вибрані статті з наукових збірників

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A finite element technique and results of continual fracture process modeling
(KNUCA, 2014) Bazhenov, V.; Pyskunov, S.
The techniques of modeling of continual fracture process for space circular and prismatic bodies under long-term static or cyclic force loading condition and some results of determination of responsible parts lifetime is presented in this paper. The scalar damage parameter is used to describe the material continual fracture process. A stress-strain problem solution made with semianalytic finite element method (SFEM). It‘s shown , that the value of residual lifetime could be differ significantly for different loading condition and object configuration.
Application of parameter continuation method for investigation of vibroimpact systems dynamic behaviour. problem state. short survey of world scientific literature
(КНУБА, 2014) Bazhenov, V. A.; Pogorelova, O. S.; Postnikova, T. G.
Authors in their works study vibroimpact system dynamic behaviour by numerical parametric continuation technique combined with shooting and Newton-Raphson’s methods. The technique is adapted to two-mass two-degree-of-freedom vibroimpact system under periodic excitation. Impact is simulated by nonlinear contact interaction force based on Hertz’s contact theory. Stability or instability of obtained periodic solutions is determined by monodromy matrix eigenvalues (multipliers) based on Floquet’s theory. In the present paper we describe the state of problem of parameter continuation method using for nonlinear tasks solution. Also we give the short survey of numerous contemporary literature in English and Russian about parameter continuation method application for nonlinear problems. This method is applied for vibroimpact problem solving more rarely because of the difficulties connected with repeated impacts.
Basic relationships for physically and geometrically nonlinear problems of deformation of primatic bodies
(КНУБА, 2020) Maksimyuk, Yu. V.; Pyskunov, S. O.; Shkril, A. A.; Maksimyuk, O. V.
The initial relations of thermo elastic-plastic deformation of prismatic bodies are given in the paper. The basic concepts, indifference of deformation tensors, with the condition of energy conjunction in description of the shaping process are laid out on the basis of classical works.
Boundary element approaches to the problem of 2-d non-stationary elastic vibrations
(КНУБА, 2020) Vorona, Yu. V.; Kozak, A. A.
Two boundary element approaches are used to solve the problem on non-stationary vibrations of elastic solids. The first approach is based on the transition to the frequency domain by means of a Fourier series expansion. The second approach is associated with the direct solution of a system of time-dependent boundary integral equations, with a piecewise constant approximation of the dependence of the unknowns on time. In both cases, a collocation scheme is used to algebraize the integral equations, and the difficulties associated with the calculation of singular integrals are overcome by replacing the kernels with the initial segment of the Maclaurin series. After such a replacement, the kernels take the form of a sum, the first term of which is the corresponding fundamental solution of the statics problem while other terms are regular. Since integration of static kernels is not difficult the problem of calculating the diagonal coefficients of the SLAE turns out to be solved. The developed techniques are compared in the process of dynamics analysis solving of elastic media with two cylindrical cavities. The boundary of one of the cavities is subjected to a radial impulse load, which varies according to the parabolic law. Both approaches have shown the similar effectiveness and qualitative consistency.
Buckling and vibrations of the shell with the hole under the action of thermomechanical loads
(КНУБА, 2020) Bazhenov, V. A.; Krivenko, O. P.
The paper outlines the fundamentals of the method of solving static problems of geometrically nonlinear deformation, buckling, and vibrations of thin thermoelastic inhomogeneous shells with complex-shaped midsurface, geometrical features throughout the thickness, under complex thermomechanical loading. The technique is based on the geometrically nonlinear equations of three-dimensional thermoelasticity, the finite element formulation of the problem in increments, and the use of the moment finite-element scheme. A thin shell is considered by this method as a threedimensional body. We approximate a shell by one spatial universal finite element (FE) throughout the thickness. The universal FE is based on an isoparametric spatial FE with polylinear shape functions for coordinates and displacements. The universal element has additional variable parameters introduced to expand its capabilities. The method of modal analysis of the shell is based on an approach that at each current stage of thermomechanical loading takes into account the stresses accumulated at the previous stages. The developed algorithm allows one to study geometric nonlinear deformation and buckling of elastic shells of an inhomogeneous structure with a thin and medium thickness, as well as to study small vibrations of the shells relative to the reference deformed state caused by static loading, taking into account large displacements and a prestressed state. An analysis of the stability and vibration of the spherical panel with the hole is carried out. The effect on the frequencies and mode shapes of the shell of the sequential action of thermal and mechanical loads is investigated.
Creation of mathematical model of platformvibrator with shock, designed for concrete products compaction and molding
(КНУБА, 2020) Bazhenov, V. A.; Pogorelova, O. S.; Postnikova, T. G.
Platform-vibrators are the main molding equipment in the production of precast concrete elements. Shock-vibration technology for the precast concrete production on low-frequency resonant platform-vibrators significantly improves the quality of the products front surfaces and the degree of their factory readiness. This technology is used to produce large elements. We describe the creation of a mathematical model for platform-vibrator that uses shock to produce asymmetric oscillations. The values of the upper and lower accelerations of the mold with concrete have different values with shock-vibration technology. The created mathematical model corresponds to the two-body 2-DOF vibro-impact system. It is strongly nonlinear non-smooth discontinuous system. It has some peculiar properties, namely: the upper body with very large mass breaks away from the lower body during vibrational motion; both bodies move separately; the upper body falls down onto the soft constraint; the impact that occurs is soft one due to the softness and flexibility of the constraint. The soft impact simulation requires special discussion. In this paper, we simulate a soft impact by a nonlinear contact force in accordance with the Hertz quasistatic contact law. The numerical parameters for this system were chosen in such a way that: firstly they provide the fulfillment of requirements for real machine, and secondly they allow analyzing its dynamic behavior by nonlinear dynamics tools. The created model is well enough to fulfill a number of requirements, namely: T-periodic steady-state movement after passing the transient process; the appropriate value of mold oscillations amplitude; the satisfactory value of the asymmetry coefficient that is the ratio of lower acceleration to the upper acceleration. We believe that the created model meets all the necessary requirements.
Dynamic behaviour of nonlinear nonsmooth discontinuous vibroimpact system
(КНУБА, 2015) Bazhenov, V. A.; Pogorelova, O. S.; Postnikova, T. G.
Authors shortly describe the problem state about studying of discontinuous vibroimpact systems dynamical behaviour. Recently the investigations of such systems are developed rapidly. There is survey of world scientific literature about this problem. Information and description of an International Conference on Nonlinear Dynamics Complexity is given. Authors show owns the most spectacular results demonstrating the phenomena unique for nonsmooth systems describing by differential equations with discontinuous right-hand side. These results were obtained by numerical parameter continuation method.
Effectiveness of semi-analytical finite element method in the numeric analysis of deformation of non-homogeneous 3d constructions subject to initial deviation of form
(КНУБА, 2015) Solodei, I. I.; Vabishchevych, M. O.; Sіzevych, B. I.; Chepurna, O. O.
Static and dynamic numeric models to analyze stress-strain state of 3D uncanonical form bodies are considered in the range of semi-analytical finite element method. Effectiveness and simulation veracity analysis are provided on the base of specific test cases.
Kyiv school of the theory of structures
(КНУБА, 2020) Bazhenov, V. A.; Perelmuter A.V.; Vorona, Yu. V.
The paper presents a review of more than a century-long history of Kyiv school of the theory of structure, the foundation of which was laid by world-famous scientists V.L. Kirpichov and S.P. Tymoshenko. The birth of the Kyiv scientific school of the Theory of structures is associated in this paper with the establishment at the Kyiv Polytechnic Institute the Strength of Materials Department. It is noted that further formation and development of the theory of structures was facilitated by the creation in 1918 of the Ukrainian Academy of Sciences, the Institute of Mechanics of the NAS of Ukraine, expansion of relevant research in higher education institutions, creation of new academic and sectoral research institutions, most of which is located in Kyiv. The contribution of Kiev scientists to the development of methods for analyzing spatial structures of bar and shell type, their inelastic behavior, as well as dynamics and stability is reflected. Particular attention is paid to the fundamentally new opportunities for the development of the theory of structures in the era of numerical analysis. The successes of Kiev mechanics in the field of development and improvement of structure analysis numerical methods, such as the finite difference method and various modifications of finite element methods, are emphasized. Kiev engineers and scientists are also known for their developments in the field of design and calculation of modern cable-stayed structures, as well as optimal design. The activities of the scientific school of structural mechanics of the Kyiv National University of Construction and Architecture are also covered in the review. In the final part of the paper the new issues connected with the justification of calculation models and the analysis of reliability of constructions are considered. Some of this problems are dictated by the demands of practice, in particular those that arosed in the process of Chernobyl New Safe Confinement designing. The publication contains a wide bibliography.
Lyapunov exponents estimation for strongly nonlinear nonsmooth discontinuous vibroimpact system
(КНУБА, 2017) Bazhenov, V. A.; Pogorelova, O. S.; Postnikova, T. G.
Lyapunov exponents are ones of the most important characteristics for the definition of the dynamical system state. Their estimation for nonsmooth discontinuous system that is vibroimpact system has got certain difficulties. We study their calculation by following the evolution of two nearby orbits in phase space and use three formulas for such estimation. We check this calculation for three different oscillatory regimes: periodic, quasi-periodic and chaotic. We also define the largest Lyapunov exponent by Benettin’s algorithm and compare obtained results.
Modeling of crack growth process in spatial bodies under cyclic loading condition
(KNUCA, 2014) Bazhenov, V.; Pyskunov, S.; Shkryl, O.
The algorithm for finite element modeling of fatigue cracks growth in the spatial bodies under cyclic loading using semianalytic finite element method (SFEM) is presented. The crack growth process is described by Paris' equation, stress intensity factor (SIF) is determined by the direct method. Testing of the algorithm is executed on the problem of the development of an elliptical crack in a prismatic body under the action of cyclic loading.
“Nonlinear Dynamics - 2016” Conference
(КНУБА, 2016) Bazhenov, V. A.; Pogorelova, O. S.; Postnikova, T. G.
There is short description of problem state on nonlinear dynamics in this paper. Information about some contemporary journals and recent Conferences on this subject is given. Information about 5th International Conference on Nonlinear Dynamics which was holding in National Technical University “Kharkov Polytechnic Institute” in September 2016 and impression about it are presented.
The parametric oscillations of rotating rods under action of the axial beat load
(КНУБА, 2020) Nedin, V. O.
The paper presents the results of investigation of the axial beat loads’ influence on the transverse rotating rods’ oscillations and their stability. The perforator's long drills are considered as objects of investigation. The analysis of different author’s papers that are studded the dynamics of oscillations of shafts and rotating rods is carried out. The relevance of the research topic is substantiated. The model of the considered dynamic system is described and equations of oscillations in space are given. The technique for investigation is presented. This technique is based on search for new bend forms of rotating rod by solving the equations of oscillations with using the Hubbolt time integration method and the polynomial functions (splines) that are described the current bend form. In it, the spline functions are found by current bend form approximation where each of the found functions is responsible to certain point of rod elastic line and describes the position of nearby points. Described technique was realized in a computer program with graphic user interface that is developed by author. Program allows to monitor for dynamics of the oscillatory motion of the modeled system in real-time by calculating and drawing the current band forms of the rotating rod during the oscillation. Diagrams with regions of stable and instable motion of the rods, that were found by different parameters and boundary conditions are shown. The analysis of the results is obtained and the conclusion about possibility of operating the equipment in certain frequency ranges is done. The space oscillating process of rotating rods is considered with account of the gyroscopic loads and geometric nonlinearity.
Thermoelasticity of elastomeric constructions with initial stresses
(КНУБА, 2020) Bazhenov, V. A.; Kozub, Yu. G.; Solodei, I. I.
The article presents an algorithm for solving linked problems of thermoelasticity of elastomeric structural elements on the basis of a moment scheme of finite elements. To model the processes of thermoelastic deformation of structures with initial stresses the incremental theory of a deformed solid is used. At each step of deformation, the stiffness matrix is adjusted using an incremental geometric stiffness matrix. The use of triple approximation of displacements, deformations and volume change function allows to consider the weak compressibility of elastomers. The components of the stress tensor are calculated according to the Duhamel-Neumann law. To solve the problem of thermal conductivity, a thermal conductivity matrix considering the boundary conditions on the surface of a finite element is constructed. A sequential approximation algorithm is used to solve the thermoelasticity problem. At each stage of the solution, the characteristics of the thermal stress state are calculated. Based on the obtained components of stress and strain tensors, the intensity of internal heat sources is calculated as the dissipative energy averaged over the load cycle. To calculate the dissipative characteristics of the viscoelastic elastomer the parameters of the Rabotnov’s relaxation nucleus are used. Solving the problem of thermal conductivity considering the function of internal heat sources allows you to specify the heating temperature of the body. At each cycle of the algorithm, the values of the physical and mechanical characteristics of the thermosensitive material are refined. This approach to solving thermoelastic problems is implemented in the computing complex "MIRELA+". Based on the considered approach, the solutions of a number of problems are obtained. The results obtained satisfactorily coincide with the solutions of other authors. Considering the effect of preload and the dependence of physical and mechanical properties of the material on temperature leads to significant adjustments to the calculated values.
Автоматизація оптимального проектування просторових систем споруд
(КНУБА, 2004) Баженов, В. А.; Слободян, Я. О.
При автоматизованому проектуванні будівельних конструкцій ставиться задача одержати найбільш економічне розв’язання, що забезпечує зниження матеріалоємності споруди. Традиційно цю задачу намагаються вирішувати шляхом розгляду обмеженого числа різних варіантів конструктивних рішень, обраних на основі інтуїції ідосвіду. Однак, аналіз показує, що при цьому навіть, у найпростіших випадках для залізобетонних конструкцій типу балок і рамних каркасів перевищення витрат матеріалів складає в середньому 7-10%, а в окремих випадках до 15-20% у порівнянні з розв’язаннями, отриманими методами оптимального проектування.
Актуальность и перспективы использования международных и национальных достижений в развитии науки, практики и образования в строительстве
(ДНДІБК, 2014) Дорофеев, В. С.; Кривошеев, П. И.; Козелецкий, П. М.; Сенаторов, В. Н.
У статті підкреслюється актуальність міжнародного співробітництва та висвітлені питання використання міжнародного та національного передового досвіду в розвитку науки, практики і освіти в будівельній галузі.
Алгоритм розв’язання вісесиметричних задач нестаціонарної теплопровідності
(КНУБА, 2015) Андрієвський, В. П.; Гуляр, О. І.; Максим’юк, Ю. В.; Мицюк, С. В.
Наведені основні розрахункові співвідношення вісесиметричних задач нестаціонарної теплопровідності в криволінійній системи координат. Проведені чисельні дослідження для обґрунтування достовірності результатів.
Алгоритм моделювання розвитку тріщини в просторових тілах із застосуванням напіваналітичного метода скінченних елементів
(КНУБА, 2004) Гуляр, О. І.; Пискунов, С. О.; Сахаров, О. С.; Шкриль, О. О.
Метою даної роботи є розробка алгоритму чисельного моделювання росту тріщини в просторових тілах, його реалізація в межах НМСЕ і проведення дослідження ефективності запропонованого підходу на прикладі призматичних просторових тіл.
Алгоритм розв’язання задач нелінійного деформування та стійкості пружнопластичних вісесиметричних оболонок середньої товщини
(КНУБА, 2014) Максим’юк, Ю. В.
Розроблена методика, яка базується на розрахункових співвідношеннях моментної схеми скінчених елементів (МССЕ), і запропонований алгоритм розв’язання систем нелінійних рівнянь пружнопластичного деформування і втрати стійкості вісесиметричних оболонок середньої товщини неканонічної форми, який дозволяє отримувати достовірні результати для широкого класу тонкостінних об’єктів.
Алгоритм розв’язання задач про коливання масивів з тріщинами поздовжнього зсуву
(КНУБА, 2010) Ворона, Ю. В.; Русанова, О. С.
На основі співвідношень методу потенціалу побудовані граничні інтегральні рівняння та чисельний алгоритм для розв’язання задачі про антиплоскі гармонічні коливання пружних масивів, послаблених плоскими тріщинами. Розв’язана тестова задача про динамічний напружений стан пружного простору поблизу тріщини поздовжнього зсуву.