Kmitání kompozitního sendvičového nosníku
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Date
2022-06-13
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Abstract
Tato bakalářská práce se zabývá vibracemi vybraných sendvičových nosníků s magneticky citlivými vrstvami z materiálu SteelFill. Tento materiál je určený pro 3D tisk a skládá se z plastové matrice plněné ocelovým práškem. Nejprve byly zkoumány dynamické a kvazistatickévlastnosti tohoto materiálu. K tomu byla využita zkouška tahem a dynamická mechanická analýza. Poté, co byly základní vlastnosti jako dynamický modul nebo Youngův modul známé, byly vyrobeny čtyři sendvičové nosníky. Každý se skládal ze dvou vnějších vrstev a jádra. Tobylo buď ze silikonové pryže, MRE nebo jejich kombinace. Nosníky byly poté vystaveny vynucenému kmitání pomocí shakeru. Tato zkouška navíc probíhala při různých intenzitách magnetického pole, které bylo vyvoláno permanentními magnety. U nosníků byly také zkoumány jejich tlumící vlastnosti. Volný konec nosníku byl vychýlen a laserový snímač sledoval časový průběh této výchylky. Po zpracování dat byly nosníkům určeny logaritmické dekrementy, které se pohybovaly v rozmezí 0,359 pro MRE2 a 0,368 pro SLC2. Hodnoty vlastních frekvencí byly určeny mezi 10 a 26,2 Hz.
This bachelor's thesis deals with the vibration of particular sandwich beams. All of the beams had a common feature, their outer layers were made of magneto - sensitive material SteelFill. This material is determined for 3D printing and consists of plastic matrix filled with steel powder. Firstly, the analysis of the Steelfill was conducted. In order to determine fundamental quasi-staticand dynamic characteristics of this material, tensile test and Dynamic Mechanical Analysis were applied. When characteristics such as dynamic modulus or Young´s modulus were known, two 3D printed thin slices were used to glue each beam together. Four specimens of beams were fabricated and each of them had a different core. All cores consisted of sillicone rubber or MRE or their combination with various lenghts. In the second part, beams were subjected to forced vibration test enabled by shaker while different magnetic fields generated by permanent magnets were applied on the beam. Consequently, a damped vibration test took place where an initial amplitude was managed simply by an external force applied to the free end of the beam. After the force was released, time course of amplitude was observed. When the last data was processed, logaritmic decrements of the beams could be determined as 0,359 for MRE2 and 0,368 for SLC2. Natural frequencies of the beams were between 10 and 26,2 Hz.
This bachelor's thesis deals with the vibration of particular sandwich beams. All of the beams had a common feature, their outer layers were made of magneto - sensitive material SteelFill. This material is determined for 3D printing and consists of plastic matrix filled with steel powder. Firstly, the analysis of the Steelfill was conducted. In order to determine fundamental quasi-staticand dynamic characteristics of this material, tensile test and Dynamic Mechanical Analysis were applied. When characteristics such as dynamic modulus or Young´s modulus were known, two 3D printed thin slices were used to glue each beam together. Four specimens of beams were fabricated and each of them had a different core. All cores consisted of sillicone rubber or MRE or their combination with various lenghts. In the second part, beams were subjected to forced vibration test enabled by shaker while different magnetic fields generated by permanent magnets were applied on the beam. Consequently, a damped vibration test took place where an initial amplitude was managed simply by an external force applied to the free end of the beam. After the force was released, time course of amplitude was observed. When the last data was processed, logaritmic decrements of the beams could be determined as 0,359 for MRE2 and 0,368 for SLC2. Natural frequencies of the beams were between 10 and 26,2 Hz.
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nosníky, kmitání, magnetické pole, vlastní frekvence, 3D tisk, beams, vibration, magnetic field, natural frequency, 3D printing