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Experimental analysis of torsion vibration of hard rubbers under large deformation
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Cibulka, Jan ; Košina, Jan
The paper deals with a stress analysis of hard rubber under large torsion deformations. This study was motivated by effort to enhance the theoretical background for experimental evaluation of material behaviour of hard rubbers on our test rig. First the Mooney Rivlin model (MRM) for shear case of loading was developed and then MRM constants were attained by fitting of the MRM to the experimental torsiondeformation curve. Then the tuned MRM cylindrical model was tested under torsion loading for evaluation of stress state. Besides the radial distribution of shear stress and strain the attention was paid to evaluation of axial stresses. It could help to assess the influence of the tension stresses on the tangential deformations of the test sample during large torsion.
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Additional axial stress of rubber cylinder at torsion deformations and large strains
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Cibulka, Jan ; Košina, Jan
The paper deals with a stress analysis of hard rubber under large torsion deformations. This study was motivated by effort to enhance the theoretical background for experimental evaluation of material behaviour of hard rubbers on our test rig. First the Mooney Rivlin model (MRM) for shear case of loading was developed and then MRM constants were attained by fitting of the MRM to the experimental torsion-deformation curve. Then the tuned MRM cylindrical model was tested under torsion loading for evaluation of stress state. Besides the radial distribution of shear stress and strain the attention was paid for evaluation of additional axial stresses. It helps to assess the influence of the tension stresses on the tangential deformations of the test sample during large torsion strains.
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Stress analysis under torsion loading hard rubber for a large deformation and hyperelastic behaviour
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Cibulka, Jan ; Košina, Jan
The paper deals with a stress analysis of hard rubber under large torsion deformations. This study was motivated by effort to enhance the theoretical background for experimental evaluation of material behaviour of hard rubbers on our test rig. First the Mooney Rivlin model (MRM) for shear case of loading was developed and then MRM constants were attained by fitting of the MRM to the experimental torsion-deformation curve. Then the tuned MRM cylindrical model was tested under torsion loading for evaluation of stress state. Besides the radial distribution of shear stress and strain the attention was paid for evaluation of axial stresses. It could help to assess the influence of the tension stresses on the tangential deformations of the test sample during large torsion.
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Measurement of modal and damping behavior of bladed disc with rhombic shroud
Pešek, Luděk ; Košina, Jan ; Cibulka, Jan
The aim of the work was modal analysis of the bladed disc with the rhombic shroud in a range up to 8kHz. The eigenfrequencies and corresponding damping ratios with respect to a number of nodal diameters were to evaluate. To obtain the maximal amplitude excitation, different types of actuators for lower frequency (up to 5 kHz) and higher frequency (above 5 kHz) ranges were used. The responses of the blades were measured by miniature accelerometers during the swept harmonic excitation. The result of the modal analysis are presented in a form of SAFE diagrams. The crossing and veering of dispersion curves appear in the SAFE diagram. It causes excitation and separation of modes very complicated problem from the identification point of view. Despite these obstacles the major part of the seeking resonances in the defined frequency range were successfully excited and identified.
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Properties of damping couple at very high frequencies
Půst, Ladislav ; Pešek, Luděk ; Košina, Jan ; Radolfová, Alena
The contribution deals with the application of dry friction couples for noise and vibration damping at high frequency of several kHz what brings new problems connected with the small amplitudes of relative slipping motion of contact surfaces. The most important information from the of experimental results is knowledge that the value of evaluated friction coefficient can have different physical sense according to the magnitude of excitation force and to the frequency of applied vibrations. If amplitudes of motion are very small, then the external harmonic force produces only elastic micro-deformations of contacting bodies, where no slip occurs and then the traction contact force is proportional only to elastic deformation of the sample.
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Dry friction characteristics of damping wire in groove
Půst, Ladislav ; Pešek, Luděk ; Košina, Jan ; Radolfová, Alena
After improvement of experimental set for measurement up to 3000 Hz, the friction properties at vibration of couples “wire - grove” diameter 14 mm was ascertained in the range 1000 – 3000 Hz, specific pressure up to 460 N/m and amplitude up to 10 mm. The abrasive wear of friction couples diameter 12 mm at 36 hour of run at 2 kHz (260 mil. cycles) has been investigated. Similar abrasive was found also on samples with anticorrosive layers.
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