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Determination of transmission error at helical gear
Czakó, Alexander ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This diploma thesis primarily deals with the transmission error issue which is one of the dominant sources of vibration in gear pairs and transmission systems. The vibrations subsequently generate noise which is often subjected to increasingly stricter demands across the industry, including the automotive one. It turns out that reducing the peak-to-peak value of the transmission error has a beneficial effect on the vibro-acoustic properties of gears and gear pairs. This thesis aims to determine the transmission error under static conditions, since a gear pair with a low static transmission error is a good assumption for a low transmission error even under dynamic effects. The resulting values of the transmission error can be influenced already during the design of the gear macro-geometry. It is also suitable to apply micro-geometric adjustments – modifications to the gear teeth. For this reason, the search part of the thesis is dedicated to theoretical knowledge, especially concerning the geometry of gears, modifications of teeth and the overall transmission error and its determination. The transmission error can be determined in several ways, including a technical experiment. However, due to time and financial reasons, this is not always possible, and therefore, the possibility of using numerical simulations is offered. In this thesis, the approach using stress-strain quasi-static contact analysis using the finite element method in Ansys Workbench software is used. The advantage is, among other things, a good comparability of results. The input to the FEM analysis is 3D CAD geometry – in this case, it is specifically a helical gear pair with parallel axes. The model/assembly of this gear pair is created in PTC Creo software fully parametrically, so it is possible to generate arbitrary gear pair configurations by changing the input parameters, which significantly saves time. At the end of this diploma thesis, the stress-strain analysis of various gear configurations is evaluated, with respect to the equivalent stress and contact pressure. Furthermore, the static transmission error – its graphs and peak-to-peak values – is determined from FEM analyses for different gear geometry, including tooth modifications, and for various loading torques. Last but not least, the effects of contact/overlap ratio and centre distance are evaluated.
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Determination of transmission error at bevel gear
Fraňová, Zuzana ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This master’s thesis deals with the determination of the transmission error in spiral bevel gears and its minimization using tooth profile modification in order to reduce vibrations and noise of transmission systems. Gears are the primary source of vibrations transmitted through the shaft and bearings to the gearbox housing and adjacent surfaces that emit noise into the surrounding space. In order to increase the level of comfort and due to the legislative requirements, increasing emphasis is being placed on reducing the noise and vibrations of machine components, including transmission systems. This leads to the need to identify noise sources and evaluate them in terms of expected acoustic performance. The quality of the gear meshing can be judged by transmission error that is closely related to the noise and vibrations. To evaluate the quality of gears based on transmission error, experimental measurements are used that are costly and require quality equipment. Therefore, it is efficient to determine the expected transmission error already at the design stage using numerical methods. In this work a parametric model of bevel gear geometry and a numerical model for the simulation of gear meshing using FEM software Ansys Mechanical are created in order to determine the transmission error. Based on the transmission error, various load cases and gear modifications designed for transmission error reduction are compared.
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Micropolar continuum and its applications in structural mechanics
Fleischerová, Beáta ; Vořechovský, Miroslav (referee) ; Eliáš, Jan (advisor)
Práca sa zaoberá mechanikou kontinua. Konkrétne je zameraná na lineárnu elasticitu homogénnych izotropných pevných telies. Pre dve rôzne kontinuá – klasické kontinuum a mikropolárne je odvodená silná aj slabá formulácia. Cosseratovo (mikropolárne) kontinuum predstavuje rozšírenie ku klasickému, kde je uvažovaný ďalší stupeň voľnosti - nezávislá rotácia. Mikropolárne kontinuum definuje ďalšie dve materiálové konštanty, ktoré súvisia s rotáciou. V súčasnosti je metóda konečných prvkov veľmi populárny spôsob približného riešenia rovníc lineárnej elasticity. Pre účely diplomovej práce bol vyvinutý program pre MKP riešenie 2D rovinných úloh. Pre lepšiu predstavu o vplyvu rôznych parametrov na správanie sa oboch kontinuí analyzujeme jednoduchý príklad konzolového nosníka. Riešenia analyzujeme s využitím 4-uzlového štvorhranného elementu, ktorý je jedným z najpoužívanejších pre MKP. V Cosseratovom kontinue by mali byť rotácie previazené skrz parameter vnútornej dĺžky, čo by sa malo odzrkadliť zvýšenou tuhosťou telesa. Úlohou práce je porovnať výsledky z oboch kontinuí a potvrdiť tento predpoklad.
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Seismic Analysis of The Pump 200-QHD
Čapičík, Martin ; Chlud, Michal (referee) ; Lošák, Petr (advisor)
The main goal of this thesis is dynamic analysis of shaft of booster pump QHD-200. In the beginning we offer basic equations generally used in dynamics and common/possible methods for their solution. Then we focus on specific problems connected with rotor dynamics and using simple Laval rotor we show their mathematical interpretation. Based on given load as accelerogram we create response spectrum in different ways (using different methods) and compare their CPU time demand. In the next part we make three finite element models of different physical level. We perform modal analysis and comparison of eigen frequencies, mode shapes. In following chapter transient analysis was performed on all models. As load we use accelerogram. We evaluate translations in particular positions of model. After that, we decide whether or not gap between impeller and stator case will be erased. Finally we make assessment of force acting upon bearings.
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Stress-strain analysis of cranial fixators
Klištinec, Dávid ; Chamrad, Jakub (referee) ; Marcián, Petr (advisor)
Zranenia hlavy si často vyžadujú lekársku starostlivosť, pri ktorej dochádza k stabilizácii alebo náhrade poškodeného tkaniva. Pre tento účel slúži kranioplastika, ktorá prinavracia pacientovi ochranný a kozmetický výsledok. Výber správneho materiálu kraniálneho implantátu je veľmi podstatný. Naviac potrebuje správny druh fixácie, ktorá ho udrží na mieste a predíde sa tak nedovolenému pohybu implantátu počas bežného života pacienta. Táto práca analyzuje deformačné a napäťové stavy dvoch druhov fixačných plátov prichytených na PMMA implantáte a ich mechanickej odozvy na rozličné záťažné podmienky spôsobené rôznymi stavmi kraniálnej hypertenzie a silou pôsobiacou na sústavu z exteriéru.
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Design of plastic pressure vessel
Rackovský, Daniel Milan ; Létal, Tomáš (referee) ; Pernica, Marek (advisor)
This bachelor thesis deals with the design of a pressure vessel made of plastic. The introductory part of the thesis contains the theoretical knowledge related to plastic materials. The next part consists of the selection of materials suitable for the design of the pressure vessel and a deeper analysis of their mechanical and other properties. The last part of the thesis deals with the calculation of the wall thickness of the plastic pressure vessel based on the theory of momentless diaphragm shells and the verification of the results using the finite element method, in Ansys Workbench 2022 R1. The analytical calculation is also compared with the calculation using the relationships given in ČSN EN 13445.
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Computational modelling of isovolumic contraction of left ventricle
Kubík, Matej ; Burša, Jiří (referee) ; Vaverka, Jiří (advisor)
This diploma thesis deals with computational modelling of isovolumic contraction of the left heart ventricle by using finite element method. Part of the thesis includes research on the anatomy and physiology of the heart, where the structure of the heart muscle is analyzed in more detail. The passive mechanical response of the model reflects this very structure. It is included in the computational model by using a reduced Holzapfel & Ogden hyperelastic model. The active tension of muscle fibers, which is a consequence of electrical stimulation, is included in the model by the so-called active stress approach. A main goal of thesis is the implementation and testing of this approach in ANSYS program with the help of subroutine Usermat.
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Static strength assessment of the weld
Gális, Róbert ; Řehák, Kamil (referee) ; Dlugoš, Jozef (advisor)
This thesis aims to review, summarize and compare the available approaches and standards assessing static strength of welds. In the introductory section, the theoretical knowledge required to assess static strength of welded structures is summarised. In the next section, the algorithms for evaluating static strength of welds using each guideline are reviewed and described in detail. They are also applied to designed T-shaped welded geometry with a two- sided fillet weld. Subsequently, the obtained results are compared and evaluated. Finally, an experiment is drafted to verify the calculations or to determine the most appropriate approach.
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Scalable thermal model of a transistor package
Klement, Matej ; Junasová, Veronika (referee) ; Otáhal, Alexandr (advisor)
Diplomová práca popisuje problematiku simulovania ohrievania diskrétnej súčiastky tranzistoru v rámci jeho vlastného zapuzdrenia. V práci boli popísané dve metódy merania teplotného odporu na základe informácií z noriem organizácie JEDEC. Model tranzistoru bol simulovaný pomocou metódy konečných prvkov v programe Ansys ICEPAK so sledovaním teploty spoju voči teplote puzdra. Časovou simuláciou ohrievania v kombinácií s menením parametrov bola vytvorená sada ohrievacích kriviek pre všetky konfigurácie tranzistoru. Ohrievacie krivky boli transformované na spektrum časových konštánt na základe algoritmov popísaných v normách JEDEC. Tieto algoritmy boli pre účely diplomovej práce implementované v programovacom jazyku Python. Jednotlivé časové spektrá boli zjednodušené do dvoj-prvkovej teplotnej siete v prevedení Foster-typu. Všetky tieto teplotné siete boli ďalej transformované do teplotnej siete Cauer-typu. Pre každý parameter v parametrickej simulácii boli vytvorené interpolačné funkcie hodnôt teplotných sietí. Na základe interpolačných funkcií bol vytvorený škálovateľný teplotný model, ktorý bol následne simulovaný v programe LTSpice a jeho výsledky porovnané s výsledkami zo simulácie metódy konečných prvkov.
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