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Verification of geometry influence on dynamic properties of immersed body
Černý, Tomáš ; Pochylý, František (referee) ; Habán, Vladimír (advisor)
Immersion of the body into the fluid creates additional effects which must be considered when designing the machines. Additional effects from the fluid influence the dynamic properties of the body. In this work the decrease of the natural frequency and the increase of the damping ratio during the gradual immersion of the body into the fluid are investigated. Diploma thesis is based on an experiment, which is performed on a series of flat strip steel components of various widths. The first three bending and first three torsion shapes of the free-hanging body are examined. Emphasis is placed on the influence of part width. In the next phase of the experiment, the influence of the proximity of the solid wall to the dynamic properties of the cantilever beam is examined. Further, the determination of the added density from the fluid is performed by modal analysis using the ANSYS software.
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Experimentální určení tlumení nosníku
Fučík, Ondřej ; Hadraba, Petr (referee) ; Rubeš, Ondřej (advisor)
This bachelor thesis deals with structural damping of metallic materials. The first part is research of damping properties, ways how to discover damping properties and short description of how to simulate viscoelasticity of materials, using mathematical models. The second part is focused on an experiment with beams of different lengths and materials. Mathematical models making is also part of solution. The third, last part is focused on results processing. Using mathematical models, damping ratios of beams are determined.
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Experimental determination of the liquid influence on an oscillating body
Grešáková, Kristýna ; Pochylý, František (referee) ; Habán, Vladimír (advisor)
Damping and natural frequency of a vibrating body or a system is not easy to estimate during the design phase of~project. If the body is submerged in water, estimating becomes even more complicated. This~work focuses on experimental determination of the liquid influence on an oscillating body. The~presented modal analysis was executed on two bodies when being surrounded by air, but~also when gradually and fully submerged in water using two reservoirs with different dimensions. The collected data was analyzed with a suggested hybrid method, which determined the damping ratio and the natural frequency. Added mass was calculated employing the Ansys software. Part of the presented work focuses on the selection of a suitable time window for the Fourier transform.
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