National Repository of Grey Literature 49 records found  beginprevious39 - 48next  jump to record: Search took 0.00 seconds. 
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.
Stability Analysis of Plane Serendipity Finite Element for Explicit Linear Elastodynamics
Kolman, Radek ; Plešek, Jiří ; Gabriel, Dušan
The central difference method is widely used for the numerical solution of the transient elastodynamics problems by the finite element method. The effectiveness of this explicit conditional stable direct time integration methods is limited by using diagonal mass matrix, which entails significant computational savings and storage advantages. However, for the serendipity type element the construction of such diagonalized matrices is not uniquely defined and various class of lumped mass matrices can be assembled. In this paper the stability analysis for the plane square serendipity finite element is performed for various class of lumped mass matrices.
Two Plates impact Problem for Testing Accuracy and Stability of Finite Element Solutions to Wave Propagation
Gabriel, Dušan ; Plešek, Jiří ; Kolman, Radek ; Valeš, František ; Ulbin, M.
The verification of comprehensive study of dispersion properties of two-dimensional bilinear and quadratic serendipity elements in transient elastodynamics on two impact plates problem was performed.
Verifikace výsledků numerické dispersní analýzy na úloze rázu dvou elastických válců
Gabriel, Dušan ; Plešek, Jiří ; Kolman, Radek ; Valeš, František ; Okrouhlík, Miloslav ; Šraml, M.
The numerical dispersion of two-dimensional finite elements was studied. The outcome of this dispersion study was verified by the numerical and analytical solutions to the longitudinal impact of two cylindrical bars. It was shown that the quadratic elements showed better accuracy than the linear ones.
Numerical test of dispersion behavirour of quadratic finite elements
Kolman, Radek ; Plešek, Jiří ; Okrouhlík, Miloslav
Numerical tests are run on the dispersion theory established for qudratic finite elements.
Dispersion Properties of Plane Quadratic Finite Elements in Elastodynamics
Kolman, Radek
Dispersion properties of quadratic finite elements in elastodynamics are derived. The relationship for the determination of the mesh density from the knowledge of the loading spectrum is presented.
Effect of time integration on dispersion properties of quadratic finite elements in elasto-dynamics
Kolman, Radek ; Okrouhlík, Miloslav ; Plešek, Jiří
In the paper, the dispersion relationships of plane quadratic finite elements for central difference method and Newmark's method are derived. The graphs for the mesh density and time step check wtih respect the dispersive behaviour are presented.
Determination of elastic moduli by the resonant ultrasound spectroscopy method
Kolman, Radek ; Plešek, Jiří ; Landa, Michal
An optimization method for the determination of elastic moduli by resonant ultrasound spectrocopy (RUS) was proposed. All components of the fourth-order tensor of elastic moduli for a general anisotropic material is determined from the knowledge of the resonance responce(spectrum) of the mechanical system. This spectrum is obtained from experimental measurements, using the RUS method on the prismatic specimen. For the iterative computation of elastic moduli an identification algorithm based on the direct iteration method is used. Spatial discretisation is performed by the finite element method.
Počítačová implementace metody FEM-RUS pro kompositní materiály
Kolman, Radek ; Plešek, Jiří ; Landa, Michal
Fixed point iteration method within the finite element discretization was developed to replace the Levenberg-Marquardt procedure. Application to bicrystals.

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