|
| |
|
|
Changes of dynamic properties of a timber frame due to simulated seismic load: a case study
Bayer, Jan ; Pospíšil, Stanislav ; Urushadze, Shota ; Kasal, B.
The data from a laboratory seismic resistance test of a three-story timber frame stiffened with steel joints were used to compare sweep and random excitation techniques on the platform of experimental modal analysis. The changes of mechanical properties due to increasing seismic load of the timber structure are demonstrated on corresponding changes of vibration modes and on changes of averaged frequency response functions. The comparison of averaged frequency response functions turned out to be at least as efficient tool for damage indication as the comparison of modal properties in this case. The experiences obtained in this case study are aimed at increasing the efficiency of dynamic tests and methods of Structural Health Monitoring.
|
|
| |
|
|
Vibration evaluation and identification in mechanical engineering
Kozánek, Jan
This paper deals with parametric identification in mechanical engineering domain. We assume a linear mathematical model of vibrating machine in discrete form and in frequency domain, defined by stiffness, viscous damping and mass matrices and by the corresponding resolvent. Parametric identification is understood as the evaluation of the measured data from dynamic experiments and its methods can be divided into "indirect" (obtaining spectral and modal properties - modal analysis methods) and "direct" (determination of the coefficient matrices of the mathematical model). We mention also the parametric identification methods for parametric and evolutive dynamic systems , the loss of asymptotic stability and dynamic systems with weak nonlinearities.
|
|
|
Modal analysis of tall slender structures using software GMAST
Hračov, Stanislav ; Pospíšil, Stanislav ; Brůna, Tomáš
The paper is concerned with a verification of modal properties of tall slender structures computed by recently developed software GMAST. Software GMAST determines eigen-frequencies, eigen-modes and corresponding modal quantities of stacks, towers, guyed masts and similar civil engineering structures using slope-deflection method. A numerical model is based on an idealization of the structure as a continuous 2D beam with continuously distributed parameters on elastic supports. Shaft of structure is divided into sections which could be considered as prismatic i.e. with constant unit mass, bending stiffness and static axial force. The effect of guy ropes is introduced in a form of elastic supports with a frequency dependent stiffness. The applicability of the software in praxis is presented on an example of existing structures, for which the numerically and experimentally identified modal properties are compared.
|
|
| |
|
| |
|
|
Numerical analysis of orhotropic properties of steel cirkular plate
Podruh, Jiří ; Pešek, Luděk
The finite element shell conservative model for free supported steel circular plate was developed. For verification of the model the experiment and analytic calculation of the first eigenvalues was performed. Relative good mutually agreement of experiment and FEM calculations was not achieved without consideration of ortotropic material properties. The contribution also deals with influence of material characteristics to the disk dynamic properties.
|
|
|
Finite element modeling of male vocal tract considering cleft palate
Dedouch, K. ; Horáček, Jaromír ; Vampola, T. ; Černý, L.
The FE models of vocal tract designed for vowel /a/ are analyzed considering the cleft palate. The first is designed using the published data, the second model corresponds to the reaal mate vocal tract designed by MRI data. Acoustic modal analysis is focused on investigation of the influence of the cleft palate on the formant frequencies. The results indicate, that after a small jump of the frequencies for a small cleft area the formant frequencies F1, F2 are influenced by the size of the cleft palate only very slightly.
|
|
|
Dynamic analysis of turbine blade M4
Hendrych, Pavel ; Pešek, Luděk ; Vaněk, František
This contribution is aimed at the numerical dynamic analysis of steam turbine low-pressure blade M4 both in steady state and under rotation. The verification of the free-free numerical model based on the modal analysis was carried out. The numerical model was developed as a three-dimensional finite element model. The Cambell diagram was calculated with respect to stress stiffening and spin softening effects.
|
guest ::
