Juraj Paulech

Effect of Non-Uniform Torsion on Elastostatics of a Frame of Hollow Rectangular Cross-Section

Abstract In this paper, results of numerical simulations and measurements are presented concerning the non-uniform torsion and bending of an angled members of hollow cross-section. In numerical simulation, our linear-elastic 3D Timoshenko warping beam finite element is used, which allows consideration of non-uniform torsion. The finite element is suitable for analysis of spatial structures consisting of beams with constant open and closed cross-sections. The effect of the secondary torsional moment and of the shear forces on the deformation is included in the local finite beam element stiffness matrix. The warping part of the first derivative of the twist angle due to bimoment is considered as an additional degree of freedom at the nodes of the finite elements. Standard beam, shell and solid finite elements are also used in the comparative stress and deformation simulations. Results of the numerical experiments are discussed, compared, and evaluated. Measurements are performed for confirmation of the calculated results.

Thermo-Hydraulic Behaviour of Coolant in Nuclear Reactor VVER-440 Under Refuelling Conditions

Abstract The paper presents the numerical simulation of thermo-hydraulic behaviour of coolant in the VVER- 440 nuclear reactor under standard outage conditions. Heating-up and flow of coolant between the reactor pressure vessel and spent fuel storage pool are discussed.

Influence of Bypass on Thermo-Hydraulics of VVER 440 Fuel Assembly

Abstract The paper deals with CFD modelling and simulation of coolant flow within the nuclear reactor VVER 440 fuel assembly. The influence of coolant flow in bypass on the temperature distribution at the outlet of the fuel assembly and pressure drop was investigated. Only steady-state analyses were performed. Boundary conditions are based on operating conditions. ANSYS CFX is chosen as the main CFD software tool, where all analyses are performed.

Modeling of Coolant Flow Within the Spent Fuel Storage Pool of a VVER 440 Reactor

Abstract The article deals with modelling of coolant flow within the spent fuel storage pool of a VVER 440 reactor. The spent fuel storage pool is modelled in a state of standard reactor operation. The coolant heating from the remaining thermal power of stored spent fuel assemblies was also modelled.

CFD Analysis of Downcomer of Nuclear Reactor VVER 440

Abstract The paper is focused on CFD analyses of the coolant flow in the nuclear reactor VVER 440. The goal of the analyses is to investigate the influence of the orifice diameter on the mass flow through individual fuel assemblies in the reactor core. The diameter of orifice can be changed during the operation of a nuclear power plant. Considered boundary conditions in the investigated region of the coolant are based on nominal coolant flow conditions in the nuclear reactor VVER 440.

ELASTOSTATIC AND MODAL AND BUCKLING ANALYSIS OF SPATIAL FGM BEAM STRUCTURES

In this contribution, a homogenized beam finite element of double symmetric crosssection made of a Functionally Graded Material (FGM) is presented, which can be used for static, modal and buckling analysis of single beams and beam structures with three directional variation of material properties. The material properties in a real beam can vary continuously in longitudinal direction while the variation with respect the transversal and lateral directions is assumed to be symmetric in a continuous or discontinuous manner. The shear force deformation effect and the effect of inertia and rotary inertia are taken into account. Additionally, the longitudinally varying Winkler elastic foundation and the effect of axial force are included by the finite element equations as well. Homogenization of spatially varying material properties to effective quantities with a longitudinal variation is done by the extended mixture rules and multilayer method (MLM). For the homogenized beam the 1212 finite element effective matrix, consisting of the linearized stiffness and consistent mass inertia terms, is established. Numerical experiments are made concerning static, modal and buckling analyses of single FGM beam and beam structures to show the accuracy and effectiveness of the proposed FGM beam finite element.

NUMERICAL SOLUTION OF DIFFERENTIAL EQUATIONS WITH NON-CONSTANT COEFFICIENTS

Abstract. Nowadays, new materials like Functionally Graded Material (FGM) are necessary for sophisticated structures like MEMS systems, advanced electronic devices, etc. Computer modelling of such complex systems, like structures with spatial variation of material properties (e.g. FGM) are, using commercial FEM code with classic elements, needs remarkable effort during preparation phase and sufficient computer equipment for solution phase because of necessity the numbers of elements and material models. Therefore new methods for modeling and simulation of FGM beams with spatial variation of material properties are developed. In the proposed contribution, semi-analytical method (based on calculation of transfer functions and transfer constants) for solution of differential equation with non-constant polynomial coefficients, is presented. This method is used in derivation process (for setting up the transfer matrix) of our new beam finite elements for modeling and simulation of Functionally Graded Material (FGM) beam structures (e.g. new 3D FGM beam finite element for modal and structural analysis, new FGM beam finite elements for coupled electro-thermo-mechanical analysis). Numerical experiments are made to show the accuracy and effectiveness of this method.

FINITE BEAM ELEMENT WITH PIEZOELECTRIC LAYERS AND FUNCTIONALLY GRADED MATERIAL OF CORE

Abstract. New smart materials have been developed in material science, that are suitable for mechatronic applications. Modern mechatronic systems are focusing on minimizing size, active control and low energy consumption. All this attributes can be incorporated into term Micro Electro Mechanical Systems (MEMS). To improve performance of MEMS system, new materials and technologies are developed one of them, which found broad application usage is Functionally graded material (FGM). MEMS application usually contains multilayer structure and in some application class MEMS systems contain piezoelectric layers. Piezoelectric structures offer facilities to make motions. Piezoelectric layers can be also used to damp vibrations as an active damping or as an active sensor. For better understanding these multiphysical problems new mathematical models are developed. The paper deals with finite beam element with piezoelectric layers and functionally graded material of core. In the paper homogenization of FGM material properties and homogenization of core and piezoelectric layers is presented. In the process of homogenization direct integration method and multilayer method is used. There is also presented the derivation of individual submatrices of local stiffness and mass matrix, where concept of transfer constants is used. Functionality of new FGM finite beam with piezoelectric layers is presented by numerical experiments.

Determining the electrical resistance of polygonal pole

This paper presents the methodology for determining the electrical resistance of polygonal pole for high voltage electric power lines. Icosahedral pole was considered where its total electrical resistance is combination of the electrical resistances of the poles material and the resistance of the slipping contacts between different poles parts. Material resistance and also coefficient of contact resistance were measured. Contact area and pressure for slip joint were calculated using finite element analysis.