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New test approach and evaluation of dynamic and thermal parameters of elastomers
Pešek, Luděk ; Vaněk, František ; Procházka, Pavel ; Bula, Vítězslav ; Cibulka, Jan ; Vaněk, Petr
The new test approaches for evaluation of thermo-visco-elastic parameters of elastomers are designed, realized and discussed herein. The main attention is devoted to a kinematic excited rubber beam sample under transient resonant sweep excitation. Mechanical material characteristics, i.e. Young modulus and loss angle, are identified from analytical formulas of FRF function based on measured dynamic loading and response signals. Heat material constants were estimated indirectly by numerical thermo-mechanical FE model and matching numerical and experimental results. The „sweep” regime tests serve for estimation of thermal and mechanical dependences. Long-term tests with cyclic resonant loading enable analysis of material degradation, such as hardening and permanent deformation, due to fatigue. For dynamic tests with pressure pulsation and sudden loading and unloading the high-power electromagnetic pulsater has been developed for damping rubber segments of tram wheels.
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Properties of thermo-visco-elastic material 42-809 for vibro-damping segment production - 3.part
Svoboda, J. ; Pešek, Luděk ; Frölich, V. ; Klášterka, Petr
The mechanical properties of rubber elements made of thermo-visco-elastic material 42 -809 at low temperatures are summarized in the report. The tests were performed in a climate chamber bought by company INOVA Prague. The chamber was built in a fatigue machine INSTRON 8502 and the temperature range is from -50 up to 180 C. For improvement of a measurement accuracy and loading the force cell with a range up to 40kN was installed. The original sample fixtures of the machine were substituted by two rods ending by supporting plate. The rods went through the bottom and top lids of the chamber. The results of static and dynamic characteristics for temperature from -50 to 0 C, measurement of residual deformation and relaxation time, evaluation of a cyclic loading influence on static characteristics and life-time characteristics for lower temperature are herein presented.
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Properties of thermo-visco-elastic material 42-809 for vibro-damping segment production
Svoboda, J. ; Pešek, Luděk ; Frölich, V. ; Klášterka, Petr
The mechanical properties of rubber elements made of thermo-visco-elastic material 42 -809 at low temperatures are summarized in the report. The tests were performed in a climate chamber bought by company INOVA Prague. The chamber was built in a fatigue machine INSTRON 8502 and the temperature range is from -50 up to 180 C. For improvement of a measurement accuracy and loading the force cell with a range up to 40kN was installed. The original sample fixtures of the machine were substituted by two rods ending by supporting plate. The rods went through the bottom and top lids of the chamber. The results of static and dynamic characteristics for temperature from -50 to 0 C, measurement of residual deformation and relaxation time, evaluation of a cyclic loading influence on static characteristics and life-time characteristics for lower temperature are herein presented.
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Teplotní účinek na rheologické vlastnosti pryžového prvku
Půst, Ladislav ; Pešek, Luděk ; Vaněk, František ; Bula, Vítězslav
Deformation and temperature data of a vibro-damping element measured in laboratory condition at harmonic loading with constant prload F st =6kN were elaborated with the aim to build termo-mechanical characteristic of rubber-like material. It is shown that the increase of temperature during harmonic loading at various amplitudes F0=(0,75,3) kN and frequencies fe(10,30) Hz is exponential in time and proportional to the square of loading amplitude. The proposed mathematical model of dynamic characteristic of specimen gained by the regression procedure consists of linear, quadratic and fourth root function of displacement amplitude Xo and of the linear correction function of temperature.
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FE model termomechanické interakce pryžového bloku při cyklickém dynamickém zatížení
Pešek, Luděk ; Šulc, Petr
The COMSOL code based on weak formulation of PDE’s problem was used at a solution of feedback thermo-mechanical interaction in pre-pressed rubber block used for resilient elements of the composed tram wheels. The structural motion and heat conduction equations are solved interactively as time dependent problems. The equality of heat energy density and dissipation energy density realizes the coupling between the equations. The dissipation energy density is computed according to the assumed proportional damping model. In the paper the results of thermo-mechanical processes in cases of a plane strain and 3D space deformation under static pre-pressed and cyclic dynamic loading are presented and analyzed.
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FEM modeling of thermo-mechanical interaction in rubber block
Pešek, Luděk ; Půst, Ladislav ; Šulc, Petr
The FEMLAB code based on weak formulation of PDE’s problem was used at a solution of feedback thermo-mechanical interaction in damping bodies by finite element method. In our approach structural motion and heat conduction equations are solved interactively as time dependent problems. The conservative energy law, i.e. equality of heat energy density and dissipation energy density, realizes the coupling between the equations. The dissipation energy density is computed according to the assumed damping model. In the contribution the results, such as temperature versus strain distribution, of thermo-mechanical processes in case of a plane strain deformation under static compression and cyclic dynamic loading concerning mechanical energy lost modeled as proportional damping, heat generation, heat transfer between rubber and outer steel parts, cooling problem and changing stiffness and damping coef.
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Hyperelesticita pryžového segmentu při jednoosých tlakových zkouškách
Potel, S. ; Pešek, Luděk ; Svoboda, Jaroslav
The plane strain model of hyperelastic material was developed in the ANSYS. For this model, hyperelastic behavior of rubber block and identification of Mooney-Rivlin coefficients from real experimental data for uniaxial compression tests are presented. Furthermore rubber-steel contact problem including tangential Coulomb forces with various friction coefficients were solved. This research is aimed at evaluation of material hyperelastic parameters from static tests and for evaluation of stress state of the rubber segments used as resilient elements in railway wheels. hicle.
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Behavior of thermo-visco-elastic material 42-809 for production of vibrodamping segments - Part I
Svoboda, Jaroslav ; Pešek, Luděk ; Fröhlich, Vladislav ; Vaněk, František ; Klášterka, Petr ; Cibulka, Jan
The report deals with the first results of rubber segment properties for vibrodamping of tram wheels. There are presented static and dynamic characteristics of force and deformation, changes of stiffness, temperature and loss factor with respect to number of cycles. In addition the growth of permanent deformation, lost of recovery, relaxation phenomena etc.
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