National Repository of Grey Literature 79 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor ; Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel ; Gabriel, Dušan ; Mračko, Michal ; Masák, Jan
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation.
Modal analysis of a rubber-suspended Stadler wheel with two variants of leaf dampers
Šnábl, Pavel ; Pešek, Luděk ; Bula, Vítězslav
The aim of this work was an experimental modal analysis of the Stadler tram wheel for two shock absorber variants: a) standard leaf shocks, b) leaf shear shocks. In the report the measurement methodology is described and the results of the modal analysis are tabulated. The results of the modal behaviour of each damper variant give an assessment of their effectiveness in suppressing significant resonances and the corresponding mode shapes. Standard leaf dampers designed as an open steel-rubber sandwich contributed most to the damping enhancement for the R3 shape, followed by R2. Newly developed leaf shear dampers provided a significant increase in damping for the R2 shape compared to standard dampers.
Dynamic tensile experiments of hard rubber on instron test machine under finite deformations
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel
This paper deals with the first experimental tests of hard rubbers under tensile harmonic loading on the axial-torsional servohydraulic Instron 8852 test machine. The objective of these experiments on cylindrical rubber specimens on this machine is to obtain stress-strain curves of rubber specimens, first considering uniaxial finite longitudinal strains for a single load cycle. Next, the hysteresis loops and their skeleton curves are compared for two selected strain measures as a function of their conjugate stress. It is shown how to obtain the dependence between elongation in the axial direction and constriction in the radial direction, which is used to determine the Cauchy stress in this configuration.
Damping of human vocal folds vibration
Radolf, Vojtěch ; Horáček, Jaromír ; Bula, Vítězslav ; Geneid, A. ; Laukkanen, A. M.
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal fold damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized on a male subject phonating on the vowel [o:]. The results show during the phonation offset a remarkable decrease of vibration frequency of the vocal folds and an increased damping ratio limiting to the value D≈ 0.2. The results for vocal folds’ damping are in agreement with previous measurements performed on humans using different methods.
Identification of material constants of rubber damping segments by modal analysis for railway rubber-resilient wheels
Šulc, Petr ; Šnábl, Pavel ; Pešek, Luděk ; Bula, Vítězslav
In this paper, an experimental and numerical modal analysis is described to assess two rubber compounds for the damping segments of a railway wheel. The subject of this comparison is materiál parameters such as Young’s modulus and loss factor for both compounds in the frequency range up to 6.5 kHz. From this comparison, an idea of the damping, stiffness and durability of these rubber segment materials inside these wheels is obtained.
Experimental investigation of the frequency-modal properties of the measuring container for LUNA mission
Zolotarev, Igor ; Bula, Vítězslav ; Šnábl, Pavel ; Snížek, Jan ; Souček, Jan
This paper continues investigations of the measuring equipment for space missions. The frequency-modal properties of the measuring container for LUNA mission were obtained by experimental investigation.
Estimation of damping in human vocal folds vibration: measurements in vivo and on model
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Košina, Jan ; Geneid, A. ; Laukkanen, A. M.
This study investigates the biomechanics of the end-part of phonation, i.e. the so-called phonation offset, experimentally. This information of vocal folds damping is important for testing and further development of mathematical modelling of phonation. The measurements of the damping ratio, based on high-speed videolaryngoscopic registrations, were realized in vivo on a male subject and in vitro using an originally developed silicon replica of the human vocal folds. In both cases the results show remarkable decrease of vibration frequency of the vocal folds and increase of damping ratio D in the phonation offset limiting to the values D=0.12 in vivo measurement and D=0.11 in vitro measurement. The results for vocal folds’ damping are in good agreement with previous measurements performed in humans using different methods.
Identification of material constants of new rubber damping segments from modal analysis of a railway rubber damped wheel
Šulc, Petr ; Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
The aim of the modal analysis was to compare and identify the material constants of two proposed mixtures of rubber damping segments of a railway wheel. The modal analysis was carried out in two stages, experimentally and then numerically. The experimental modal analysis was carried on a rubber-suspension wheel for the two proposed rubber types of segment , designated 42809 and 46809. From this dynamic analysis, the natural frequencies and eignemodes of the wheel oscillations were obtained in the frequency bandwidth up to 6.5kHz. The material constants of the rubber were obtained by tuning the material parameters of the rubber segments, i.e. elastic modulus and special proportional damping coefficient, of the 3D FEM model of the railway wheel to the values of natural frequencies and damping ratios of the selected wheel natural vibration modes.
Modal analysis of a container with measuring equipment for space mission
Zolotarev, Igor ; Bula, Vítězslav
This paper continues investigations of some measuring equipment for space mission. The frequency-modal properties a container with several slots and measured desks are studied. The natural frequencies and corresponded modes obtained using measuring methods are presented for several combinations of the container components.
Verification of our deformation member for measuring axial force under torsional dynamic load
Šulc, Petr ; Pešek, Luděk ; Štěpánek, Ivo ; Šnábl, Pavel ; Bula, Vítězslav
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we focused on obtaining axial forces and elongation, which is a confirmation of the so-called Poynting effect under torsional loading. An important result from these experiments is a comparison of axial forces from this device with the results from our designed and assembled torsion device with a deformation member for measuring axial forces, which brings us some verification of this device.

National Repository of Grey Literature : 79 records found   1 - 10nextend  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.