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scientific edition of Bauman MSTUSCIENCE & EDUCATIONBauman Moscow State Technical University. El № FS 77  48211. ISSN 19940408
Mechanics
Integration possibilities of the chain theory methods and the automatic control theory in solving tasks of dynamics of machines
# 06, June 2012 DOI: 10.7463/0612.0378699 Possibilities of creation of structural schemes of mechanical oscillation systems are considered in this article. The authors propose an integration method which combines possibilities of using principles of electromechanical analogies (mechanical chains) and rules of structure transformations with feedback coupling. A methodological base for evaluating dynamic properties of vibration protection systems with electromechanical couplings was proposed.
7730569/377653 Change of dynamical properties of mechanical oscillation systems on the base of introduction of link connection
# 04, April 2012 The authors consider questions of creating mathematical models of mechanical systems with couplings. Usually the couplings are simple rotational kinematical ties. The authors propose a method of model creation – this method consists of implementation of a certain sequence of actions based on selection of points of possible coupling of two bodies and a system of corresponding coordinates. If the elements of the planned coupling are identified as points of possible contact and are interconnected with an elastic or dissipative coupling, the difference between the coordinates of two selected points defines the relative coordinate. This coordinate can be removed out of the coefficient matrix of the system of motion equations with an appropriate column and line delineation. Coupling introduction is accompanied with a decrease in the number of degrees of freedom. Several examples, including one for two couplings, are considered in the article.
Concept of feedback coupling in dynamics of mechanical systems and dynamical damping of oscillations
# 05, May 2012 DOI: 10.7463/0512.0378353 The authors propose a methodical foundation of estimation and research of origination of dynamical damping of oscillations for tasks of vibration protection of machines and equipment. The novelty of the approach consists of using a new class of mathematical models for mechanical systems; these models represent structural schemes as the equivalent of dynamic systems of automatic control. The authors consider questions of scientific substantiation of structural transformations of mathematical models with selection of feedback couplings, inherent in elastic oscillation systems. A dynamical oscillation damper in the vibration protection system within the framework of the developing concept was considered as feedback of a certain type. The authors propose a technology of detection of dynamical damping of frequencies in systems with several degrees of freedom. The authors show possibilities of improvement of the “dynamical damping of oscillations” concept the physical meaning of which essentially depends on the choice of synthesis coordinates. The authors propose a synthesis method for building vibration protection systems with dynamical absorbers of oscillations. The numeric simulation and laboratory experiment results are included in the article.
7730569/362856 Axisymmetric oscillations of dualdensity liquid in the cylindrical tank
# 04, April 2012 This article considers a model problem for a funded system of capillary suction device of a spacecraft fuel tank. Two fluids undergoing a joint motion with a flexible membrane are considered. Axisymmetric vibrations of the system, dynamic and kinematic conditions impact on the membrane, irrotational fluid motion are explored. The author introduced the velocity potential of fluid, for which the Laplace equation can be written. The Laplace equation was solved by Fourier method. The dynamic boundary conditions for a membrane were obtained by the characteristic equation for natural frequencies of the vibration of joint fluids and membrane. The dynamic characteristics of the oscillatory system were defined by their dependence on the geometric parameters of the tank.
7730569/353180 Mathematical simulation of contact interaction of elastoplastic environments
# 04, April 2012 The authors consider an algorithm of solving of a contact problem of the theory of elastoplasticity on the basis of alternating Schwarz method. The article includes a numerical solution of the theory of elasticity contact problem with the use of implementation of an iterative process of the alternate appointment of displacement vectors and surface forces on surfaces of the contact, and also their corresponding correction. The authors consider the mechanism with account of friction and elastoplastic deformations when solving contact problems with the use of the developed algorithm. Results of numerical simulation of contact interaction of heated bodies are included in the article. The geometry of finiteelement models of contacting bodies after deformation is shown.
7730569/332595 Algorithm of automatic construction of meshes from quadrangular finite elements
# 02, February 2012 An algorithm for construction of finite element models consisting of quadrangular finite elements for twodimensional domains with complex geometric design was developed. The main distinctive feature of the proposed algorithm by comparison with the existing ones was a possibility of construction of irregular meshes in multicoherent areas without their preliminary splitting into the onecoherent. It was established that meshes in areas of canonical form had expressed structured character, but meshes in areas with curved boundary were irregular. The developed algorithm can be used in the general finite element technology for solving the thermomechanical problems, which arise at creation and operational development of objects of the aviation and space technics.
7730569/330203 The variational method of the least fatigue for calculating the optimum trajectory of active motion
# 01, January 2012 In present work we propose a mathematical model of horse fatigability and then using the model we derive motion equations with the help of calculus of variations. The equations are solved in general integral form and then numerically taking in account Yin & Yang boundary conditions at the point of entering (or leaving) the circle. The results are presented in graphic form and supplied with the discussion. Trajectories, obtained in this paper, are equally applicable not only for horses, but for other actively moving objects such as motorcycles, bicycles, race cars etc.
7730569/318597 Transverse migration of particles in the boundary layer of planeplate
# 02, February 2012 A comparison of known experimental data with numerical simulation of dispersed mixture flow in the boundary layer of a horizontal/vertical plane wall was carried out. The motion of that mixture was described with the model of interpenetration continuums; the influence of particles on carrier phase was neglected. Qualitative agreement between the calculated concentration profiles of particles with the experimental data was obtained. Taking the lateral force into account correctly described the experimental effects of local maximums of the particle concentration inside the boundary layer and the decrease of the concentration near the wall.
7730569/318125 Mathematical model of axially symmetric vortex motion
# 02, February 2012 This article deals with the structure of confined vortex motion. A mathematical model was proposed, and boundary conditions of vortex motion based on the Helmholtz theorem were formulated. A theory of vortex motion in the field of mass centrifugal forces was introduced. The developed mathematical model and formulated boundary conditions allowed to study the main features of motion which appear in vortex devices and to determine the influence of the chamber’s parameters on flow regime.
7730569/311247 Localization of a critical section along the length of a bridge span basing on experimental data
# 04, April 2012 The author considers the problem of localization of a hidden fracture in a bridge span, basing on the experimental data analysis. Monitoring system, which allows to record spectrums of natural frequencies of certain spans of a bridge, was developed at the “Apparatuses and systems of orientation, stabilization and navigation” department of BMSTU. It was shown in the article that analysis of fractional variation of the first six frequencies of each span of a bridge makes it possible to localize the critical section.
7730569/311032 The analyses of natural frequencies of the bridge structures in the process of crippling
# 03, March 2012 This article deals with the problem of marker determination; these markers allow to locate hidden fractures in individual bridge spans. The frequency method for investigation of oscillation in systems with distributed parameters was used for the analysis. A known mathematical model – the model of pinended beam with point load  was used because additional weight would lead to the decrease of the main natural frequency, just like a fracture would do in this place. The decision analysis of the wave equation allows to identify dependences of changes in the first six frequencies subject to the place of critical section. A set of values of frequency reducing on different harmonic components could be regarded as an attribute of the critical section area. This conclusion may be of significant practical importance when analyzing results of bridge monitoring.
7730569/310721 Numerical simulation of cylindricalconical barrels’ interior ballistics with plastic projectile body
# 03, March 2012 The authors consider numerical simulation of interior ballistics of cylindricalconical barrels and describe mathematical models of propellant and plastic medium in mass Lagrangian coordinates. The numerical solution was obtained by using a simplified Neumann finitedifference scheme. It is shown that the use of a cylindricalconical barrel with a plastic body allowed to increase the initial velocity of the projectile by about 1.5 times compared to classical schemes.
7730569/309571 About kinematics and loading of support structure of horse’s front leg at the stage of ground approaching as a part of fourfooted engine’s operational cycle.
# 04, April 2012 The experimentalbased analysis of kinematics and loading of horse's front legs at the stage of "step" and "trot" allures were presented in this paper for hoof landing preparation phase. Estimations of linear and angular speeds were given; stress pattern of the leg as a mechanism with variable structure were produced with simple calculations. Estimation of hoof’s damping properties and determining of damping power characteristic were also given. This paper was based, in fact, on the author's investigation that has been described in [8].
7730569/308455 Tunable acoustic filters based on the corrugated tubes
# 02, February 2012 The author briefly describes the theory of acoustic resonator based on the corrugated tubes. For easy understanding, a situation with medium at rest inside a corrugated tube was considered. Classical solutions for the resonator were obtained. It was shown that the described structure could serve as an acoustic analogue of the optical resonator. Generalizations for the case of moving medium were made.
7730569/300281 Development of the method of stabilization of pump unit’s platform
# 01, January 2012 DOI: 10.7463/0112.0300281 The method of stabilization of the trunk pump unit (TPU) was presented in this article. Since TPU increased oil pressure during its transportation through the pump, the heavy shear force arose. This force was applied to pipes, which had been jointed to the pump, and to unit frame. To reduce the influence of negative shear force it was offered to compensate this force with system of hydrocylinders
7730569/300828 Hydraulic accumulator: working parameters dependence from its effective volume of liquid
# 01, January 2012 The mathematical model of hydraulic accumulator performance was described in this article. The mathematical model was based on equations of the ideal gas law and the soft shells theory. Developed model allowed to analyze various hydraulic accumulator operating regimes numerically. The aim of this article was to compare the obtained results with the experimental data, i.e. to understand whether the created model was correct.



