CC BY
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5. ФЗ № 273-ФЗ от 21.12.2012 «Об образовании в Российской Федерации».
References
1. Viktorova T. S., Mushkatov M. S. Transition from remote training to electronic at the present stage. Electronic resource. Access mode: http://www.architektura-btlarusi.ru/PUBLIKACn/perehod_ot_distancionnogo_obucheniy_k_elektronnomu/ (date of the address of 27.11.2014).
2. Korniyenko S. A. Electronic training as implementer of an educational program [Text] / S. A. Korniyenko//Pedagogics: traditions and innovations: materials V междунар. науч. конф. (Chelyabinsk, June, 2014). - Chelyabinsk: Two Komsomol members, 2014. - Page 175-182.
3. Novgorodova N. G. Engineering course design in information graphic space. [Text]: materials междунар. науч. - a method. конф. "Informatization of engineering education" of IN-FORENO-2014 (on April 15-16, 2014). M.: National research university "MEI", 2014. -Page 257-261.
4. Novgorodova N. G., Chubarkova E.V. Formation of professional mobility in information society. Social and professional mobility in the XXI century: collection of materials and reports Mezhdunar. конф. Yekaterinburg, on May 29-30, 2014 / under the editorship of G. M. Romantsev, V. A. Kopnov. Yekaterinburg: Publishing house of Dews. the state. the prof. - пед. un-that, 2014. - 352 pages of ISBN 978-58050-0535-1 - Page 82-87.
5. Federal Law No. 273-FZ of 21.12.2012 "About education in the Russian Federation".
Петров М.Г.
Кандидат технических наук, Сибирский научно-исследовательский институт авиации имени С.А. Чаплыгина ПРОГНОЗИРОВАНИЕ ДОЛГОВЕЧНОСТИ ЭЛЕМЕНТОВ КОНСТРУКЦИЙ НА ОСНОВЕ МОДЕЛЕЙ МАТЕРИАЛА
КАК ФИЗИЧЕСКОЙ СРЕДЫ
Аннотация
Методология прогнозирования долговечности конструктивных элементов основывается на кинетической концепции разрушения. Случайные процессы нагружения и температурных флуктуаций моделируются суммированием элементарных случайных функций. Дан ряд примеров расчётных оценок долговечности конструктивных образцов из металлических сплавов при случайных процессах нагружения и когерентных процессах нагружения и нагрева. Эта методология даёт возможность решить те задачи, которые ещё не были решены.
Ключевые слова: долговечность, разрушение, неупругость, случайные воздействия.
Petrov MG.
PhD in Engineering, Siberian aeronautical research institute named after S.A. Chaplygin
LIFE PREDICTION OF STRUCTURAL DESIGN BASED ON MODELS OF MATERIAL AS A PHYSICAL MEDIUM
Abstract
The methodology of life prediction of structural components is based on the kinetic concept offracture. Random processes of loading and temperature fluctuations are simulated by a summing of unit random functions. A set of examples is given to calculate life evaluations of structural components under random processes of loading and coherent processes of loading and heating. This methodology enables one to solve those problems which are yet not been worked.
Keywords: longevity, failure, inelasticity, random effects.
Introduction
Danger regions of structures, where macro cracks appear, are subjected to combined effects of various forces. The nominal stresses from several components of loads, which can be inter-correlated random processes, are considered as conditions of failure. The temperature stresses can be another parameter that is related with temperature at critical location of structure partially or completely. The problem on life prediction of structures consists in the determinations of point and time of macro cracks appearance in its elements under concurrent effects of random and determinate constituents of loads and temperature variations.
Solution of the problem
Strength is the interdisciplinary area. The problem is solved in the framework of kinetic concept of fracture, which considers the plastic deformation and accumulation of damages in materials as thermally activated processes [1]. The methodology of life prediction of structure elements supposes the use of three groups of models: models of materials, models of structure elements and models of external effects.
We have introduced new bodies into rheology that describe plastic flow and plastic hysteresis of solids in terms of the theory of rate processes [2, 3]. Composed of rheological bodies, the structural model of material represents formally internal thermodynamic processes in alloys and responds to external effects similar to the material itself. We take, as criterion of fracture, concentration criterion [4, 5], which is accepted obeying for individual structural element of material model.
The models of structure elements are used for reproducing of stress-deformed conditions in danger regions of structure. Their challenge is to associate the nominal stresses (or strains) with the strains in the critical locations of structure elements in time. The model of structure element integrally with the material model forms calculated model of danger region of structure and describes processes of stress and plastic strain variations and of accumulation of damages in critical location.
To simulate the external effects as random processes the theory of random functions has been taken, whereby the random process is presented as a sum of unit random functions (URF) [6, 7]. The equivalent pseudo-random process with discrete spectrum as a sum of harmonic URF is of use as simplest model of actual random process with predetermined standard statistical characteristics. The representing of random process by the sum of URF allows the use of discrete process in the form of piece-linear dependence both in experiments and in computations. The amplitude and frequency modulations of harmonic URF do better about saving in the calculation time and about desired impact.
The temperature and time appear in the solutions of differential equations of material model in explicit form; this being so, the problem of reproducing the arbitrary conditions of structure loading is attacked by piece-linear approximating of actual determined or equivalent pseudo-random processes of force and temperature effects. All processes of external effects break down into time stages, for every of which mathematical expectation, spectral density, and distribution law of current values of process are determined.
The discretion degree of spectrum of equivalent pseudo-random process is adopted as dictated by material of structure element, by stress concentration factor and a root-mean square deviation (RMSD) of process. It can be expressed quantitatively by the following formula:
Dd = E Df D2
where Dt is dispersion of i-part of process at this located frequency, D is a total dispersion of process, and Z is a number of spectrums lines. If the process is presented by harmonic functions of equal amplitudes, so will Dd = 1/Z [7]. In Table are given the test results of two types structural specimens with variable concentration factor at constant value of spectral density of process presented by distinct number of harmonics of equal amplitudes. Here RMSSR is root-mean square scatter ratio - the life logarithm RMSD’s antilogarithm. It is more descriptive characteristic of scatter.
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