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Search results for: body of revolution (bor), cylindrical waveguides, finite-element method (fem), generalized impedance matrix (gim), periodic structures, scattering, waveguide discontinuities.
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Modelling of Longitudinal Elastic Wave Propagation in a Steel Rod Using the Discrete Element Method
PublicationThe paper deals with the issue of modelling elastic wave propagation using the discrete element method (DEM). The case of a longitudinal wave in a rod with a circular cross-section was considered. A novel, complex algorithm consisting of the preparation of models and simulation of elastic waves was developed. A series of DEM models were prepared for simulations, differing in discretisation and material parameters. Additional calculations...
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A new duty cycles calculation method in pulse width modulation for direct matrix converters based on the shape function concept
PublicationPaper presents a new approach to duty cycle calculation in pulse width modulation for direct matrix converters. The essence of the proposed method is the use of elementary shape function of finite element. The algorithm for calculating the duty cycles was reduced to simple operations on the coordinates of input and output voltage vectors without trigonometric functions.
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Scattering by parallel cylindrical posts with conducting strips.
PublicationRozwinięto teorię rozpraszania fali elektromagnetycznej w obszarach otwartych i zamkniętych na metalizowanych obiektach cylindrycznych przy użyciu zmodyfikowanej procedury iteracyjnej i metody dopasowania rodzajów. W wyniku analizy uzyskano pole rozproszone w przypadku struktur otwartych oraz odpowiedzi częstotliwościowe współczynników odbicia i transmisji w prostokątnych złączach falowodowych. Obrót i przemieszczenie opisywane...
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Ultrasonic Tomography of Brick Columns Based on FEM Calculations
PublicationUltrasonic tomography is one of the most developed method of non-destructive testing. Despite being used mainly in medicine, it is becoming more and more popular as a method for monitoring of structural elements. It allows to examine the internal structure and technical condition of the tested element. This paper investigates the influence of crosssectional geometry on an obtained tomographic image. Wave propagation signals were...
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Impact of the Finite Element Mesh Structure on the Solution Accuracy of a Two-Dimensional Kinematic Wave Equation
PublicationThe paper presents the influence of the finite element mesh structure on the accuracy of the numerical solution of a two-dimensional linear kinematic wave equation. This equation was solved using a two-level scheme for time integration and a modified finite element method with triangular elements for space discretization. The accuracy analysis of the applied scheme was performed using a modified equation method for three different...
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BIOLOGICAL TRACE ELEMENT RESEARCH
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A finite element analysis of thermal energy inclination based on ternary hybrid nanoparticles influenced by induced magnetic field
PublicationThe use of hybrid nanoparticles to improve thermal processes is a key method that has implications for a variety of interventions utilized in many sectors. This paper aimed to look into the impacts of ternary nanoparticles on hyperbolic tangent materials to establish their thermal characteristics. Flow describing equations have been explored in the presence of heat production, non-Fourier heat flux, and an induced magnetic field....
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Simulation of water flow in double -porosity soils on unstructured grids with the finite element method.
PublicationRozważa sie model przepływu wody w gruntowym ośrodku o podwójnej porowatości. Model matematyczny uzyskano poprzez zastosowanie teorii homogenizacji zastosowanej do gruntów o bardzo dużej różnicy przepuszczalności.
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Spectral Finite Element Method for Propagation of Elastic Waves in Wind Turbine Blades for SHM
PublicationW pracy przedstawiono model łopaty turbiny wiatrowej zbudowany z wykorzystaniem spektralnych elementów skończonych. Omówiono wyniki symulacji propagacji fal sprężystych i ich interakcji z uszkodzeniami w formie pęknięcia i delaminacji.
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Comparative modeling of shear zone patterns in granular bodies with finite and discrete element method
PublicationW artykule przedstawiono wyniki numeryczne naporu piasku na ściankę szczelną. Obliczenia wykonano stosując metodę elementów dyskretnych i skończonych na bazie mikropolarnego hipoplastycznego prawa materiałowego. Porównanie obu podejść wykonano na poziomie makro i mikro. Wyniki numeryczne porównano także z wynikami doświadczalnymi.
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M-integral for finite anti-plane shear of a nonlinear elastic matrix with rigid inclusions
PublicationThe path-independent M-integral plays an important role in analysis of solids with inhomogeneities. However, the available applications are almost limited to linear-elastic or physically non-linear power law type materials under the assumption of infinitesimal strains. In this paper we formulate the M-integral for a class of hyperelastic solids undergoing finite anti-plane shear deformation. As an application we consider the problem...
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Uncertainty estimation of loop impedance measurement determined by the vector method
PublicationThis article presents a detailed analysis of uncertainty estimation of loop impedance measurement determined by the vector method. The analysis includes the following estimates: resistance variance, voltage variance and time measurement variance. This paper presents a methodology for estimating the combined standard uncertainty of loop impedance by the vector method. The vector method allows to determine loop impedance based on...
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An isogeometric finite element formulation for geometrically exact Timoshenko beams with extensible directors
PublicationAn isogeometric finite element formulation for geometrically and materially nonlinear Timoshenko beams is presented, which incorporates in-plane deformation of the cross-section described by two extensible director vectors. Since those directors belong to the space R3, a configuration can be additively updated. The developed formulation allows direct application of nonlinear three-dimensional constitutive equations without zero...
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Evaluation of the fast impedance spectroscopy method in the laboratory measurement system
PublicationIn this paper the method for fast impedancespectroscopy of technical objects with very high impedance(|Zx| ≥ 1 GΩ) is evaluated by means of simulation and practicalexperiment. The method is based on excitation of an object, witha square pulse and measurements of voltage and currentresponses with DAQ card. The object impedance spectrum isobtained with use of continuous Fourier transform. Someimprovements of the method concerned...
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A higher order shell element for wave propagation in isotropic shell structures
PublicationThe presents the new multi mode higher order shell element for wave propagation problems in shell structures.
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Electrostatic interactions in finite systems treated with periodic boundary conditions: Application to linear-scaling density functional theory
PublicationWe present a comparison of methods for treating the electrostatic interactions of finite, isolated systems within periodic boundary conditions (PBCs), within density functional theory (DFT), with particular emphasis on linear-scaling (LS) DFT. Often, PBCs are not physically realistic but are an unavoidable consequence of the choice of basis set and the efficacy of using Fourier transforms to compute the Hartree potential. In such...
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A three-dimensional periodic beam for vibroacoustic isolation purposes
PublicationThis paper presents results of investigations on a three-dimensional (3-D) isotropic periodic beam. The beam can represent a vibroacoustic isolator of optimised dynamic characteristics in the case of its longitudinal, flexural and torsional behaviour. The optimisation process concerned both the widths as well as the positions of particular frequency band gaps that are present in the frequency spectrum of the beam. Since the dynamic...
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An isogeometric finite element formulation for boundary and shell viscoelasticity based on a multiplicative surface deformation split
PublicationThis work presents a numerical formulation to model isotropic viscoelastic material behavior for membranes and thin shells. The surface and the shell theory are formulated within a curvilinear coordinate system,which allows the representation of general surfaces and deformations. The kinematics follow from Kirchhoff–Love theory and the discretization makes use of isogeometric shape functions. A multiplicative split of the surface...
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Parametrized Local Reduced-Order Models With Compressed Projection Basis for Fast Parameter-Dependent Finite-Element Analysis
PublicationThis paper proposes an automated parametric local model-order reduction scheme for the expedited design of microwave devices using the full-wave finite-element method (FEM). The approach proposed here results in parameterized reduced-order models (ROMs) that account for the geometry and material variation in the selected subregion of the structure. In each subregion, a parameter-dependent projection basis is generated by concatenating...
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A simple finite difference approach using unstructured meshes from FEM mesh generators.
PublicationPrezentujemy metodologię używania dwuwymiarowych różnic skończonych wykorzystujących siatki trójkątne z metody FEM. Określiliśmy wyrażenia opisujące pierwsząi drugą pochodną w oparciu o wartości pól w saśiednich punktach. Metodę przetestowaliśmy na strukturze rezonatora z prostokątnym rdzeniem dielektrycznym.
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Cost-Effective and Sufficiently Precise Integration Method Adapted to the FEM Calculations of Bone Tissue
PublicationThe technique of Young’s modulus variation in the finite element is not spread in biomechanics. Our future goal is to adapt this technique to bone tissue strength calculations. The aim of this paper is to present the necessary studies of the element’s integration method that takes into account changes in material properties. For research purposes, a virtual sample with the size and distribution of mechanical properties similar...
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Improved finite element method for flow, heat and solute transport of Prandtl liquid via heated plate
PublicationIn the current study, a vertical, 3D-heated plate is used to replicate the generation of heat energy and concentration into Prandtl liquid. We discuss how Dufour and Soret theories relate to the equations for concentration and energy. In order to see how efectively particles, interact with heat and a solvent, hybrid nanoparticles are used. It does away with the phenomena of viscous dissipation and changing magnetic felds. The motivation...
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Magnetic switching of Kerker scattering in spherical microresonators
PublicationMagneto-optical materials have become a key tool in functional nanophotonics, mainly due to their ability to offer active tuning between two different operational states in subwavelength structures. In the long-wavelength limit, such states may be considered as the directional forward- and back-scattering operations, due to the interplay between magnetic and electric dipolar modes, which act as equivalent Huygens sources. In this...
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Fast High-Impedance Spectroscopy Method Using SINC Signal Excitation
PublicationIn this paper the method of fast impedance spectroscopy of technical objects with high impedance (|Zx| > 1 Gohm) is evaluated by means of simulation and practical experiment. The method is based on excitation of an object with a sinc signal and sampling response signals proportional to current flowing through and voltage across the measured impedance. The object impedance spectrum is obtained with use of continuous Fourier transform...
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FEM modeling of structures based on close range digital photogrammetry
PublicationPraca dotyczy metodologii przygotowania modelu konstrukcji istniejącej do analizy mechanicznej metodą element ow skończonych. MOdelowanie geometrii budowli jest oparte na danych pozyskanych z pomiarów fotogrametrycznych. Praca wskazuje na możliwości oraz efektywność zastosowania metod optometrycznych w rewitalizacji budowli zabytkowych, an przykładzie modelu dachu drewnianego.
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Sophistication assessment of existing FEM models of orbital blowout trauma: Is models valuation justified?
PublicationAfter a thorough study of the work entitled “Development and validation of an optimized finite element model of the human orbit”, some doubts aroused concerning the sophistication assessment of the existing finite element method (FEM) models of orbital blow-out. Although the work was unquestionably innovative, and the results were not only fascinating but also invaluable, the authors stated that their model was the most sophisticated...
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ESTIMATION OF YOUNG`S MODULUS OF THE POROUS TITANIUM ALLOY WITH THE USE OF FEM PACKAGE
PublicationPorous structures made of metal or biopolymers with a structure similar in shape and mechanical properties to human bone can easily be produced by stereolithographic techniques, e.g. selective laser melting (SLM). Numerical methods, like Finite Element Method (FEM) have great potential in testing new scaffold designs, according to their mechanical properties before manufacturing, i.e. strength or stiffness. An example of such designs...
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Application of the Finite Element Method for Modelling of the Spatial Distribution of Residual Stresses in Hybrid Surface Layers
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Modelling and parameter identification of steel–concrete composite beams in 3D rigid finite element method
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A new anisotropic bending model for nonlinear shells: Comparison with existing models and isogeometric finite element implementation
PublicationA new nonlinear hyperelastic bending model for shells formulated directly in surface form is presented, and compared to four existing prominent bending models. Through an essential set of elementary nonlinear bending test cases, the membrane and bending stresses of each model are examined analytically. Only the proposed bending model passes all the test cases, while the other bending models either fail or only pass the test cases for...
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Propagation in the Open Cylindrical Guide of Arbitrary Cross Section With the Use of Field Matching Method
PublicationA simple solution to propagation problem in open waveguides and dielectric fibers of arbitrary convex cross section is presented. The idea of the analysis is based on the direct field matching technique involving the usage of the field projection at the boundary on a fixed set of orthogonal basis functions. A complex root tracing algorithm is utilized to find the propagation coefficients of the investigated guides. Different convex...
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Biomechanics of Lumbar Spine Injury in Road Barrier Collision–Finite Element Study
PublicationLiterature and field data from CIREN database have shown that lumbar spine injuries occur during car crashes. There are multiple hypotheses regarding how they occur; however, there is no biomechanical explanation for these injuries during collisions with road safety barriers (RSBs). Therefore, the objective of this study was to investigate the mechanics of vertebral fractures during car collisions with concrete RSBs. The finite...
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Step on It Bringing Fullwave Finite-Element Microwave Filter Design up to Speed
PublicationThere are many steps in the design of a microwave filter: mathematically describing the filter characteristics, representing the circuit as a network of lumped elements or as a coupling matrix, implementing the distributed elements, finding the initial dimensions of the physical structure, and carrying out numerical tuning using electromagnetic (EM) simulators. The whole process is painstaking and time-consuming, and it requires...
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Immunizing the Hillcast Method against the Known-Plaintext Attack using Periodic Key Exchange
PublicationThis paper considers a Joint Fingerprinting and Decryption method, called Hillcast, for the copyright protection and traitor tracing in case of Video on Demand services. Because the method is based on the Hill cipher, it is vulnerable to a known-plaintext attack. The goal of this paper is to present an efficient periodic key exchange mechanism to make this method secure without compromising its scalability, imperceptibility or...
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Ireneusz Kreja dr hab. inż.
PeopleGraduated from the mathematical class at the Nicolaus Copernicus High School in Gdańsk (1974). Master of Sciences in Civil Engineering after studies at Gdansk University of Technology (GUT), Poland (1974-1979). Since 1979 became an employee of the GUT. In 1989 earned a Ph.D. degree in Civil Engineering (with grade "Summa cum Laude") from the GUT. In 2008 obtained a D. Sc. (Habilitation) degree in Civil Engineering (with grade...
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Bow-Tie cylindrical posts in a rectangular waveguide and its filter applications
PublicationRozwinięcie teorii rozpraszania fali elektromagnetycznej w mikrofalowych złączach falowodowych na dwuwymiarowych, cylindrycznych obiektach typu ''Bow-Tie'' przy użyciu zmodyfikowanej procedury iteracyjnej i metody dopasowania rodzajów. Wynikiem analizy są odpowiedzi częstotliwościowe współczynników odbicia i transmisji w prostokątnych złączach falowodowych zawierających opisywane obiekty. Struktura typu ''Bow-Tie'' składa się z...
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Effective method for determining environmental loads on supporting structures for offshore wind turbines
PublicationThis paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates) pyramids of polygon with a large number of sides (8 or more). The presented computational method is based on the Morison equation, which was originally...
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Effective method for determining environmental loads on supporting structures for offshore wind turbines
PublicationThis paper presents a description of an effective method for determining loads due to waves, current and wind acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates) pyramids of polygon with a large number of sides (8 or more). The presented computational method is based on the Morison equation, which was...
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Application of a hybrid finite difference-mode matching method to the analysis of circular cavities loaded with cylindrical metallic objects
PublicationW artykule przedstawiono badania rezonatorów cylindrycznych zawierających obiekty cylindryczne o dowolnym przekroju poprzecznym z wykorzystaniem metody hybrydowej stanowiącej połączenie metody różnic skończonych z metodą dopasowania rodzajów. W ramach badań określono częstotliwości rezonansowe dla wybranych struktur rezonatorów. Wyniki numeryczne zostały zweryfikowane eksperymentalnie.
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Periodic Properties of 1D FE Discrete Models in High Frequency Dynamics
PublicationFinite element discrete models of various engineering 1D structures may be considered as structures of certain periodic characteristics. The source of this periodicity comes from the discontinuity of stress/strain field between the elements. This behaviour remains unnoticeable, when low frequency dynamics of these structures is investigated. At high frequency regimes, however, its influence may be strong enough to dominate calculated...
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Generalized Zero Range Potentials and Multichannel Electron Molecule Scattering.
PublicationZagadnienie o rozpraszaniu elektronów na molekułach rozwiązuje się w sposób jawny w modelu potencjałów o zerowym promieniu. Uwzględniając stany wzbudzone wprowadzamy potencjał macierzowy. Dla przykładu stanów wibracyjnych e+H_2 porównujemy wyniki obliczeń przekrojów czynnych z innymi (ab initio) oraz z doświadczeniem.
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A Novel Bitrate Adaptation Method for Heterogeneous Wireless Body Area Networks
PublicationIn the article, a novel bitrate adaptation method for data streams allocation in heterogeneous Wireless Body Area Networks (WBANs) is presented. The efficiency of the proposed algorithm was compared with other known algorithms of data stream allocation using computer simulation. A dedicated simulator has been developed using results of measurements in the real environment. The usage of the proposed adaptive data streams allocation...
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A Novel Bitrate Adaptation Method for Heterogeneous Wireless Body Area Networks
PublicationIn the article, a novel bitrate adaptation method for data streams allocation in heterogeneous Wireless Body Area Networks (WBANs) is presented. The efficiency of the proposed algorithm was compared with other known algorithms of data stream allocation using computer simulation. A dedicated simulator has been developed using results of measurements in the real environment. The usage of the proposed adaptive data streams allocation...
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Portico Farmhouses of the Vistula Delta: Architecture, Current State and Finite Element Modelling of Timber Roof Truss under Material and Cross-section Uncertainty
PublicationThe article focuses on the oldest surviving I-type portico houses located in the Vistula Delta, which were built in the 17th and 18th centuries. The study describes the houses’ origins, structure, details of roof structures and technical condition, and it also includes numerical modelling of a roof truss and its mechanical analysis. Numerical models of the roof trusses are defined and analysed by means of the finite element method....
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Updating Finite Element Model of a Wind Turbine Blade Section Using Experimental Modal Analysis Results
PublicationThis paper presents selected results and aspects of themultidisciplinary and interdisciplinary research oriented for the experimental and numerical study of the structural dynamics of a bend-twist coupled full scale section of awind turbine blade structure.Themain goal of the conducted research is to validate finite elementmodel of themodified wind turbine blade section mounted in the flexible support structure accordingly to the...
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FINITE GROUND CPW-FED UWB ANTENNA OVER THE METALLIC CYLINDRICAL SURFACES
PublicationThe investigation of finite ground coplanar fed ultra-wideband (UWB) antenna and the influence of its curvature and the proximity of circular metallic screen on the reflection coefficients and radiation characteristics is presented. The antenna is composed of two circular coplanar strips which enclose slot aperture of similar shape and is designed on a thin and flexible substrate which allows its bending. The antenna configuration...
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Generalized Taylor formula and shell structures for the analysis of the interaction between geosythetics and engineering structures of transportation lines
PublicationThe analysis of the interaction between geosynthetics and engineering structures (e.g. railroad bed, soil foundation, pipeline) assumes that the geosynthetic form elastic membranes or shell laid on different types of foundations. The mathematical description of that problems in continuous domain employs Laplace operator Δ or d’Alembert operator □. In this paper we demonstrate the analysis based on generalize Taylor formula, and...
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A New Type of Macro-Elements for Efficient Two-Dimensional FEM Analysis
PublicationThis letter deals with a model order reduction technique applicable for driven and eigenvalue problems solved using the finite element method (FEM). It allows one to efficiently compute electromagnetic parameters of structures comprising small features that require strong local mesh refinement. The subdomains of very fine mesh are separated from the global domain as so called macro-elements that undergo model reduction. The macro-elements...
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3-D finite-difference time-domain modelling of ground penetrating radar for identification of rebars in complex reinforced concrete structures
PublicationThis paper presents numerical and experimental investigations to identify reinforcing bars using the ground penetrating radar (GPR) method. A novel element of the paper is the inspection of different arrangements of reinforcement bars. Two particular problems, i.e. detection of few adjacent transverse bars and detection of a longitudinal bar located over or under transverse reinforcement, have been raised. An attention was also...
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Four-node semi-EAS element in six-field nonlineartheory of shells
PublicationW pracy sformułowano 4-węzłowy powłokowy element skończony dla konstrukcji powłokowych. Element opracowano w ramach nieliniowej 6-parametrowej teorii powłok z niesymetrycznymi miarami odkształceń membranowych. Kinematyka powłoki jest opisana przez dwa pola: translacji i obrotów, przy czym wszystkie trzy parametry obrotu traktowane są jako niezależne. W wyniku tego sformułowany element nadaje się do analizy struktur powłokowych...