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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.
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Identifikace materiálových konstant nových pryží tlumících segmentů z modální analýzy železničního pryží odpruženého kola
Šulc, Petr ; Pešek, Luděk ; Šnábl, Pavel ; Bula, Vítězslav
Cílem modální analýzy bylo porovnat a identifikovat materiálové konstanty dvou navržených směsí pryžových tlumících segmentů železničního kola. Modální analýza byla řešena ve dvou etapách, a to experimentálně a následně numericky. Experimentální modální analýza probíhala v laboratoři ÚT s použitím jednobodového buzení (SIMO) na gumo-odpruženém kole, a to pro obě navržené varianty pryžových segmentů s označením 42809 a 46809. Z této dynamické analýzy byly získány vlastní frekvence a tvary kmitání kola v pásmu do 6,5kHz. Materiálové konstanty pryže byly získány na základě ladění materiálových parametrů pryžových segmentů, tj. modulu pružnosti a koeficientu speciálního modelu proporcionální tlumení, 3D MKP modelu železničního kola na hodnoty vlastních frekvencí a poměrných útlumů vybraných tvarů vlastního kmitání kol.
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Contribution to modelling of bladed model disk with dry-friction contacts in tie-bosses
Pešek, Luděk ; Šnábl, Pavel ; Šulc, Petr ; Půst, Ladislav ; Bula, Vítězslav
The experimental set-up for studying dynamical behavior of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tiebosses based on 3D finite element method with surface to surface dry friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behavior and damping estimation of our bladed wheel design yielded a reasonable agreement. Limitation of the non-linear solution due to dry friction contacts is HPC computations and long computation times. The contribution will deal with the achieved results.\n
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Testing of HPD model of dissipated energy of hard rubbers at torsional finite Deformations and temperatures
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel
This paper deals with the temperature dependence of hard rubber behavior on torsional harmonic loading. This behavior was described by dissipated and deformation energy of the rubber. This knowledge was used to test the validity of the hyperelastic proportional damping (HPD) in dependence on temperature and finite deformations. From the experiments, the dissipated energy was obtained from the hysteresis loop in one period of harmonic load, depending on the temperature for the given frequency. The deformation energy was determined from the shear stress analysis on the surface of the cylinder considering hyperelasticity. The constants of these models were obtained by optimizing the stress-strain curve from the shear analysis on the cylinder surface. With this optimization, the Yeoh hyperelastic model was chosen.
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Influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox
Šulc, Petr ; Pešek, Luděk ; Maturkanič, Dušan
This contribution is continuation of the work of above mentioned authors to whom this paper is dedicated. Their latest work dealt with numerical modelling of dynamics of planetary gearboxes with four satellites on flexible pins. They programmed the gear-box model in SIMULINK and now the model is an object of numerical investigations. This contribution describes the numerical model of the planetary gearbox. The numerical simulations are aimed to study an influence of variable stiffness in toothed gears on the internal dynamics of the planetary gearbox.
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