Národní úložiště šedé literatury Nalezeno 49 záznamů.  začátekpředchozí31 - 40další  přejít na záznam: Hledání trvalo 0.00 vteřin. 
EUROMECH Colloquium 540 - Advanced Modelling of Wave Propagation in Solids
Kolman, Radek ; Berezovski, A. ; Okrouhlík, Miloslav ; Plešek, Jiří
The Euromech Colloquium 540 - Advanced Modelling of Wave Propagation in Solids took place at the Institute of Thermomechanics in Prague from 1st to 3rd October 2012. It aimed at bringing together engineers and scientists interested in modelling of wave propagation in solids. The Colloquium focused on topics related to effects in linear and non-linear wave propagation in solids. Recent advances in numerical and analytical approaches and strategies were discussed. The main purpose of the Colloquium was to discuss novel methods of wave propagation modelling and to assess the credibility of results especially in cases when experiment validation had not been available.
Frictionless contact of elastic bodies: comparison of treatment in finite element analysi and isogeometric analysis
Kopačka, Ján ; Kolman, Radek ; Gabriel, Dušan ; Plešek, Jiří
Artificial oscillations in contact force due to non-smooth contact surface are treated by isogeometric analysis (IGA). After brief overview of B-splines and Non-Uniform Rational B-Splines (NURBS) representation, the mortar-based contact algorithm is presented in the frictionless small deformation regime. Contact constraints are regularized by penalty method. The contact algorithm is tested by means of contact patch test.
Mass lumping methods for the semi-loof shell element
Sháněl, Vít ; Kolman, Radek ; Plešek, Jiří
Mass matrix diagonalization in terms of a finite element method (FEM) is essential for an effective deployment of the explicit method as one of the direct integration methods of the motion equations of elastodynamics. A particular attention is focused on the mass matrix diagonalization of the semi-loof shell element. Its diagonalization requires a specially designed universal diagonalization scheme that is derived from the scaling HRZ method. Another analyzed aspect is the problem of preserving the moment of inertia for various types of finite elements. The proposed scheme is implemented in the finite element program and consequently tested on several problems
Estimation of the critical time step for explicit integration
Plešek, Jiří ; Kolman, Radek ; Gabriel, Dušan
Explicit integration plays a key role in many problems of linear and non-linear dynamics. For example, the finite element method applied to spatial discretization of continua leaves a system of ordinary differential equations to be solved, which is often done by the central difference method.
B-spline finite element method in one-dimensional elastic wave propagation problems
Kolman, Radek ; Plešek, Jiří ; Okrouhlík, Miloslav
In this paper, the spline variant of finite element method (FEM) is tested in one-dimensional elastic wave propagation problems. The special attention is paid to propagation of stress discontinuities as an outcome of the shock loading and also to spurious oscillations occurring near theoretical wavefronts. Spline variant of FEM is a modern strategy for numerical solution of partial differential equations.
Diagonalizace matice hmotnosti u skořepinového prvku typu semiloof
Sháněl, Vít ; Kolman, Radek ; Plešek, Jiří
Zvláštní pozornost je věnována diagonalizaci matic hmotnosti skořepinovému prvku typu semiloof. Diagonalizace matice hmotnosti v metodě konečných prvků má zásadní význam pro efektivní využití explicitních přímých integračních metod pro řešení problémů elastodynamiky.
SIGA 2011
Kolman, Radek ; Linkeová, I. ; Okrouhlík, Miloslav ; Pařík, Petr
The conference SIGA 2011 aimed to bring together mathematicians, physicists, computer designers and engineers dealing with splines who are using them for the numerical solutions of partial differential equations of various problems in mechanics and physics. In computational mechanics, it is isogeometric analysis (IGA) which is being dynamically developed. This numerical method employs shape functions based on different types of splines (B-splines, NURBS, T-splines and many others), and the fields of unknown quantities are consequently described the same way as the geometry of the studied domain. In addition, this approach provides a higher degree of continuity than that offered by the classical finite element (FE) method based on Lagrangian polynomials. Isogeometric analysis aims to integrate FE ideas in CAD systems without necessity to regenerate mesh. The conference intends to create a forum for further discussion in multidisciplinary scientific areas involving mathematics, computer graphics, geometry, physics, engineering and software engineering, respectively.
Jednorozměrná disperzní analýza B-Spline varianty metody konečných prvků
Kolman, Radek ; Plešek, Jiří ; Okrouhlík, Miloslav ; Gabriel, Dušan
V tomto příspěvku je studováno disperzní chování B-spline varianty metody konečných prvků a tyto výsledky jsou porovnány s klasických přístupem varianty metody konečných prvků.
Analysis of classical and spectral finite element spatial discretization in one-dimensional elastic wave propagation
Kolman, Radek ; Plešek, Jiří ; Okrouhlík, Miloslav ; Gabriel, Dušan
The spatial discretization of continuum by finite element method introduces the dispersion error to numerical solutions of stress wave propagation. For higher order finite elements there are the optical modes in the spectrum resulting in spurious oscillations of stress and velocity distributions near the sharp wavefront. Spectral finite elements are of h-type finite element, where nodes have special positions along the elements corresponding to the numerical quadrature schemes, but the displacements along element are approximated by Lagrangian interpolation polynomials. In this paper, the classical and Legendre and Chebyshev spectral finite elements are tested in the one-dimensional wave propagation in an elastic bar.
Stabilitní analýza rovinného kvadratického konečného prvku pro explicitní lineární elastodynamiku
Kolman, Radek ; Plešek, Jiří ; Gabriel, Dušan
Metoda centrálních diferencí se často používá pro numerické řešení přechodových úloh elastodynamiky. Tato explicitní podmíněně stabilní metoda přímé integrace pohybových rovnic je velice efektivní pouze ve spojení s diagonální maticí hmotnosti. Pro kvadratické konečné prvky není diagonální matice jednoznačně definována na rozdíl od lineárních prvků. V tomto příspěvku je provedena stabilitní analýza rovinného čtvercového kvadratického prvku pro celou třídu přípustných diagonálních matic hmotnosti prvku.

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