Кафедра "Рухомий склад та колії"

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ENG: Department of Rolling Stock and Track

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Longitudinal Vibrations of Viscoelastic Longitudinally Nonuniform Rod under Power Load Distributed Along its Length
(Lviv Polytechnic National University, Lviv, 2016) Gera, Bogdan V.; Sitarz, Marek; Bolzhelarskyi, Yaroslav V.
EN: In this article, the dynamic behavior of a moving elongated object is simulated using the relations for a viscoelastic rod, which moves at a constant speed under the action of traction force and distributed along its length external forces of resistance. We investigate the change of displacements and internal forces after the sudden application in the rod section of the local force directed longitudinally. The correlations of the initial boundary value problem that describes the dynamic behavior of the rod are written down, and its solution is obtained in the form of a series expansion in terms of eigenfunctions. For a viscoelastic rod consisting of three connected uniform rods, the analysis of wave processes induced by the application to the rod of a sudden concentrated force that resists the motion is carried out. This affects the motion of the rod as a whole, and induces the wave processes, the propagation and reflection of waves on the inner surfaces of joints. The comparison is performed for the behavior of an elastic, piecewise nonuniform rod and a viscoelastic rod with different mechanical characteristics, where the waves during their propagation are damped and smoothed.
A Study of the Effects of Climatic Temperature Changes on the Corrugated Structure of a Culvert of a Transportation Facility
(PC "Technology Center", Ukrainian State University of Railway Transport, Kharkov, 2019) Gera, Bogdan V.; Kovalchuk, Vitalii V.
EN: The results of experimental studies of temperature distribution on the surface of a metal corrugated sheet are presented. It is assumed that temperature depends on two spatial variables. As a possible criterion for the selection of the desired function of temperature distribution structure minimization of the functional defined on the set of admissible functions in the form of an integral over the body region from the expression that determines the entropy production is taken. In the study of the temperature field, the differential equation of thermal conductivity is used, and the stress-strain state is the equation of the theory of thermal elasticity. The finite difference method was used to solve the differential thermal conductivity equation and the finite element method was used to solve the thermoelasticity equations. It is established that the temperature is distributed unevenly by metal corrugated sheet. There is a temperature difference between the lower and upper surfaces of the corrugated metal sheet. The temperature difference between the lower and upper surfaces of the sheet is +7.1 ° C at maximum additional ambient temperatures and –5.5 ° C at minimum negative temperatures environment. It is established that the magnitude of stresses that occurs in metal corrugated sheets from environmental temperature differences, up to 25% of the allowable stresses. Therefore, when designing metal corrugated structures, it is necessary to calculate the effect of temperature climatic influences. The obtained data of thermal stress of corrugated metal structures are important for design organizations. Since, given the effect of the temperature field on the stressn state of the structure as a whole at the design stage, it is possible to select materials in order to reduce the temperature stresses that have a direct impact on the development corrosion damage to metal pipe.