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1

The domain decomposition approach with contact problem

Podesva J.

Modelling and Optimization of Physical Systems

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2010

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z. 9

65--70

CS

Modelování valivého ložiska přináší dva významné problémy. U kontaktního problému předpokládame, že dva povrchy se budou dotýkat. Dotyk přenáší tlakovou sílu, ne však tahovou. Není dopředu jasné ani jak velka bude kontaktní plocha, ani jaké bude rozložení kontaktního tlaku. Druhým problémem může být velikost úlohy. Dnešní hardware sice umožňuje rychlé řešení velkých úloh. Přesto při poćtu stupňů volnosti v řádu 105 až 106 a při použití algoritmů, vyžadujících opakování výpočtu, může toto představovat problém. Účinnou cestou řešení může být dekompozice modelu na tzv. „super-prvky“. Příspěvek přináší popis modelování s použitím super-prvků a doplnění modelu o kontaktní prvky.

EN

The large structure with contact problem appears while modeling the roller bearing. Nowadays the hardware allows solving the large systems of equations. Nevertheless if the number of DOF goes over 105 or 106 and the algorithm necessitates the iterative approach this could be the problem. The effective way of solution can be domain decomposition. The contact problem means that two surfaces touch one another. The contact transmits the pressure force but not tensile force. The paper brings the description of modeling with super-elements and solving the contact problem.

2

The e-learning teaching features

Podesva J

Modelling and Optimization of Physical Systems

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2008

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z. 7

95--98

EN

Mechanics is a structuralized subject based on the exact definitions and mathematical formulation. It is hard to study it "mechanically" directly into the human memory. It is necessary to understand the inner structure of subject, to understand "the behavior" of mechanics. The role of the living teacher is not substitutable. From the other point of view sometimes for students, especially in distance learning, it is difficult to attend the lectures. The e-learning is way to create learning easy to understand.

3

The modelling of the 2-D anisotropic continuum

Hoskova D., Podesva J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2006

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z. 31

55-58

EN

The paper is focused to the 2-D continuum - the fiat fabric material. The fabric material represents the anisotropic continuum. The description of the general anisotropic material, types of anisotropy and the calculation of the physical constants ofthe stiffness matrix are mentioned in the paper. The second part of the paper is focused to the methodology of the "flexi tank" modeling. The "flexi tank" is the light equipment for transport and storage of fluids. The anisotropic material properties are accompanying by the geometrie non-linearity. The deformation, the stress state and the volume of the fluid are results of the modeling.

4

The methodology of the beam stiffness calculation

Podesva J., Janas P.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2006

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z. 31

131-134

EN

The calculation of the horizontal mine opening steel support can be performed by the special program, developed on the Department of Civil Mechanics (Faculty of Civil Engineering, VŠB - Technical University of Ostrava). It can take into account the geometrical non-linearity (large displacement), but other effects, like plasticity and stiffhess decrease due to change of the support section are not able to include into calculation. The paper describes the possibility to express these effects like the change of the beam stiffhess E • J.

5

Modeling of physical and geometric non-linearities of the steel arch supports on the FEM basis

Podesva J., Janas P.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2005

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z. 28

125-128

EN

The steel arch support of the horizontal mine openings represents the steel structure, made up on the beam elements. There exists a number of computer programs for the force and stress analysis of such structures. The geometric non-linearity (large displacement) can be included into the program code. But after the large change of the beam cross sectional area, and under plastic deformation, the beam partially looses its stiffness. This feature is hard to include into the beam-based model. The paper introduces the kind of "trick" how to take into account the influence of the beam-shape change and non-linear plastic material model.

6

The gear mechanism for the Stirling engine

Podesva J., Mika J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2004

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z. 25

125-132

EN

The Stirling engine is the type of the gas engine which trades off the external combustion. The mechanism of the engine consists of two pistons which closes two volumes, connected together through cooler, regenerator and warmer. The effectiveness of the engine depends (except of other influences) on the piston movement regime. Standard sinusoidal movement leads to low effectiveness. The movement with quick change of the position and then short stay in the higher and lower position is more effective. The paper describes three mechanisms, managing the piston movement, and their skills with special focus to the piston movement regime.

PL

Silnik Stirlinga jest rodzajem silnika gazowego o zewnętrznym spalaniu. Mechanizm silnika składa się z dwóch tłoków zamykających dwie objętości połączonych razem przez chłodnicę, regenerator i podgrzewacz. Skuteczność silnika zależy m.in. od technicznych warunków pracy tłoka. Ruch z szybką zmianą pozycji, a następnie krótka przerwa w najwyższej i najniższej pozycji są bardziej efektywne. W artykule przedstawiono trzy mechanizmy odpowiedzialne za nich tłoka i sterujące ruchem tłoka.

7

The non-linear 3D model of the rail seating

Podesva J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2003

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z. 22

87-92

EN

The rail is placed on the seating and on the sleeper. The rubber pad is placed between the sleeper and the seating and also between the seating and the rail. The flat and rather stiff pad is for the electric isolation. To decrease the influence of forces (due to weight of the train) to the load of the sleeper and to the degradation of the gravely bed the use of massively sorter pad with the contact protrusions is prepared. The layer system concrete sleeper - rubber pad - steel seating - rubber pad - rail is pre-stressed. This leads to the initial load of the seating. Under the train weight the load of the seating changes and the fatigue effect appears. The static analysis results from two load steps - the pre-stressed unloaded seating and the train weight load - are the inputs to the fatigue analysis.

8

The support of the commercial fem software to the original computational methods

Podesva J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2000

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z. 12

75-78

EN

A specific problem in the mechanics of large, discretized systems is reduction of the number of degrees of freedom. Some of the existing and known methods are supported by the commercial software, sonie of them are not. But in several ways the commercial software can help in using of the newly developed, directly not supported methods. In the paper the modal synthesis method is introduced and the ways of indirect support of the commercial package (Ansys) are described.

PL

Szczególnym zadaniem w mechanice dużych dyskretyzowanych obiektów jest redukcja stopni swobody. Część znanych metod jest wspomagana komercyjnym oprogramowaniem, część z niech nie jest, lecz w kilku przypadkach oprogramowanie komercyjne może wspomagać użytkowanie nowych, bezpośrednio nie wspomaganych metod. W artykule opisano metodę syntezy modalnej i sposób pośredniego wspomagania obliczeń komercyjnym pakietem Ansys.