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Proposal of shaft alignment method for small rotors using digital image correlation
Hrůza, Vlastimil ; Pokorný, Jan (referee) ; Ščerba, Bořek (advisor)
The presented thesis deals with the design of a method for aligning small rotors, for which commonly available methods are not suitable. This is due to space restrictions around the coupling, which often do not allow installation of conventional alignment systems on the shafts. The proposed method therefore utilizes non-contact measurement of the surface of the shafts using digital image correlation (DIC). Calculation of misalignment and corrective moves is based on fitting the points measured on individual shafts with cylinders and evaluating the mutual position of their axes. To determine the area of applicability of the proposed method, sensitivity analysis was performed, which showed that the method gives good results for surface-accurate shafts with a uniformly applied speckle pattern for DIC measurement. Validation of the method was then carried out by measuring on a designed test rig using a commonly available laser alignment system. The validation measurement proved the functionality of the method and confirmed the conclusions of the sensitivity analysis.
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Gear coupling modification
Mahel, Pavel ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis deals with the design of a gear coupling. The main intention is to design the optimal shape of the clutch gearing for the given operating conditions. Due to the special barrel shape of the teeth on the external gearing, these couplings enable the torque to be efficiently transmitted even in the case of misalignment of the connected shafts. In the case of an improperly designed coupling, a number of problems can occur that could affect the life of the coupling. These problems include in particular the generation of excessive vibrations and noise. It is necessary to choose the right lubrication system for long-term coupling life. To eliminate problems with gear couplings, it is necessary to ensure a suitable distribution of contact pressure at a given degree of misalignment. The introductory part of the thesis contains a comprehensive view of the issue of gear couplings. The next part deals with the structural design of the whole gear coupling and the improvement of the existing model. The following is a description and analysis of two different computational models of gearing that allow for different maximum degree of misalignment. The difference between the two gearing models is in the different geometry of the tooth shape on the hub. In the computational analysis, the most important monitored parameter was the course of contact pressure on individual teeth at a given degree of misalignment. From the performed computational analyses, result files are processed that compare the contact pressure and the number of teeth in engagement for different degrees of misalignment. The above analyses were performed using the finite element method in the calculation program Ansys Workbench.
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Vibrodiagnostics of electrical machines
Petráček, Samuel ; Cipín, Radoslav (referee) ; Janda, Marcel (advisor)
This bachelor's thesis deals with getting to know vibrations and their description. What types of vibrations occur, what are their parameters, such as deflection or acceleration, and a slightly described frequency analysis for non-harmonic signals. Subsequently, the sources of vibrations in electric rotating machines are described. Types of vibration sources are described here, for example of mechanical origin or on the bearing. The causes of their occurrence are, for example, rotor imbalance, rotor misalignment or mechanical loosening. And their subsequent effect on the machine in axial and radial directions. Furthermore, the Crest Factor measurement method and a summary of other diagnostic methods of vibrodiagnostics such as Envelope Analysis and Kurtosis Factor are described. For what purposes these methods are used and their advantages and disadvantages. In the practical part, 4 asynchronous motors were measured with prerequisites for faults with rotor eccentricity. The effective values of the vibrations and the Crest Factor were calculated here, followed by a frequency analysis using FFT (Fast Fourier Transform). In the end, the resulting data were evaluated.
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Performance and Safety Improvement of Large-Scale Hydrostatic Bearings
Michalec, Michal ; Wodtke, Michal (referee) ; Fillon, Michel (referee) ; Svoboda, Petr (advisor)
Táto dizertačná práca sa zaoberá experimentálnym a numerickým štúdiom veľkorozmerných hydrostatických ložísk. Takéto ložiská sa používajú na presné a plynulé polohovanie veľkých konštrukcií, pretože klzné plochy ložiska sú úplne oddelené externe tlakovaným mazacím filmom. Od jeho prvého oficiálneho predstavenia v roku 1852 prebehol rozsiahly výskum na zlepšenie výkonnosti. Napriek tomu sa výskumníci primárne zameriavali na hydrostatické ložiská malých rozmerov, zatiaľ čo len veľmi malá časť výskumu sa zameriavala na väčšie rozmery tohto typu ložísk. V takýchto prípadoch vznikajú úplne iné výzvy, ktoré sú spojené s vyššou energetickou náročnosťou, výrobou dielov ložísk, dopravou a montážou. Výrobné chyby, nesprávne zarovnanie ložísk alebo neoptimálna konštrukcia môžu zhoršiť výkonnosť ložiska, čo môže viesť až k jeho poruche. Cieľom tejto dizertačnej práce je predstaviť vylepšenia výkonu a bezpečnosti do rozsiahlej metodiky návrhu hydrostatických ložísk. Zlepšenie výkonu ložiska sa vykonáva pomocou numerického modelu oblasti tekutiny, ktorý je overený pomocou experimentálnych a teoretických údajov. Táto štúdia predstavuje úplne nový prístup založený na nezávislej optimalizácii viacerých geometrických parametrov hydrostatickej ložiskovej kapsy. Zlepšenie bezpečnosti sa vykonáva čisto experimentálne. Pozornosť je zameraná na nesúosovosť klzných plôch kapsy a bežca a ich vplyv na výkon ložísk. Okrem toho je skúmaná schopnosť samo-vyrovnávania podložky s použitím poddajnej podstavy. Experimentálna časť bola vykonaná pomocou testovania hydrostatického ložiska pozostávajúceho z dvoch káps s plnou diagnostikou. Ako ukazujú výsledky, navrhovaná metodika optimalizácie geometrických parametrov hydrostatického ložiska môže zlepšiť výkon ložiska až o 20 %. Skúmanie vplyvov nesúosovosti na výkonnosť ložiska ukazuje určitý rozsah, v rámci ktorého môže ložisko stále bezpečne fungovať, zatiaľ čo poddajná podpora môže tento rozsah ešte predĺžiť. Táto štúdia predstavuje originálny výskum rozširujúci poznatky o rozsiahlych hydrostatických ložiskových systémoch smerom k lepšiemu výkonu a vyššej bezpečnosti.
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Stress strain analysis of membrane coupling
Sýkora, Tomáš ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This master’s thesis deals with the strain stress analysis of a membrane coupling with different membrane shapes and under different operating conditions. Thanks to their flexible membrane, these couplings are able to transmit torque even in the moment of misalignment of the connected shafts. However, too much misalignment is one of their most common causes of failure. For this reason, it is necessary to define the critical areas of the coupling during the design and to reduce these areas with the right optimization. For this purpose, a geometric and subsequently a numerical model of the membrane coupling for simulations using FEM software Ansys Workbench is created. At the beginning, the initial shape of the membrane is determined and according to the results of individual simulations, the shape is gradually optimized. At the end of the thesis, based on the distribution of equivalent stress in the membrane, the results of individual optimizations are compared and evaluated.
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Vibrodiagnostics of electrical machines
Boháček, Daniel ; Vítek, Ondřej (referee) ; Janda, Marcel (advisor)
This thesis deals with methods of vibration analysis in electric rotating machines. From the beginning, it is necessary to explain the basic concepts and introduce the issue of vibration. Next time, the work is focused on sources of vibration in electrical machines. Defects on electric rotating machines causing vibrations are described. Sensing is performed using sensors of deflection, speed and acceleration. The measured signal needs to be adjusted and filters, approximations and sampling will cover this in the next chapter. The main objective is the methods of analysis, which include the best known in the field of frequency analysis (FFT) and the envelope method in the time domain. This includes other methods such as Kurtosis factor, Crest factor, etc. There is also a basic block diagram for measuring vibrations. This block diagram is programmed and has a graphical user interface. The last part is an evaluation of the measured data of the engines.
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Strain-stress analysis of gear coupling
Vondra, Róbert ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This thesis deals with the contact analysis study of crown gear couplings during the simulation of its working conditions. The toothed coupling transmits high torque, even when the input and output shafts are misaligned due to outside tooth shape. For this reason, it is necessary to design the gear shape correctly. The inherent use of toothed couplings results in a wide range of working speeds and load transfers. This can cause several problems, if the parameters are selected incorrectly. Among the most significant of these is the generation of vibrations during gear engagement, accompanied by noise and the excessive loading of components, such as shafts and bearings. It is not possible to completely reduce uneven running, even with knowledge of the latest trends in the field of gear development. For this reason, it is necessary to eliminate the paths where the vibrations can propagate during the design itself. Inefficient and costly experiments are often used to determine the correct shape of gear teeth. For this purpose, a computational approach to describe a contact pressure on the teeth of couplings at different misalignment and loads is proposed. The model helps to understand the composition of the contact pressure during the working mode of misalignment and its behaviour within the rotation of the gear coupling. The introductory part of thesis presents the current state of knowledge of gear couplings and a description of load distribution issues, regarding the angular misalignment, torque and friction. In the following chapter, three possible approaches to the problem are described - analytical, experimental and computational. The following work offers the introduction and creation of two different computational models, varying in different tooth shape on the hub and the sleeve. Each geometry was subjected to a different load moment, a misalignment of the hub, or the rotation of the gear coupling as a whole. The main monitored parameter was the course of contact pressure in each step, when changing the degree of misalignment or the rotation of the model. Finally, three main sets of contact pressure on the teeth are presented, in connection with the reduced pressure plotted on the toothed rings. There is derivation of results and mutual comparison of each load case. The computation approach in FEM program Ansys Workbench was used to solve the problem.
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Design of a test stand for vibrodiagnostics education
Doležal, David ; Huzlík, Rostislav (referee) ; Zuth, Daniel (advisor)
The master's thesis on the topic "Design of a Testing Model for Vibrodiagnostics Education" deals with the construction issues of the device. The introductory section provides a systematic analysis, which serves as the basis for the subsequent work. The literature review section discusses Technical Diagnostics with a focus on its subfield, Vibrodiagnostics. It also describes various types of sensors used for vibration measurements. Subsequently, typical faults of rotors and their configuration are presented. The thesis then focuses on the design of the testing device. The design emphasizes simplicity, ease of manufacturing, and minimizing production costs while maintaining functionality and reliability. After the suitable design was proposed, the testing device was manufactured and its functionality was tested in a school laboratory. Several measurements were conducted on different types of faults, such as static unbalance and moment unbalance. The measurements also considered misalignment due to the lack of device calibration. The final part of the thesis evaluates the testing device and provides recommendations for possible improvements. The outcome of the work is the creation of a functional testing model for diagnostic education, which has been tested and is operational.
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Stress strain analysis of membrane coupling
Sýkora, Tomáš ; Prokop, Aleš (referee) ; Řehák, Kamil (advisor)
This master’s thesis deals with the strain stress analysis of a membrane coupling with different membrane shapes and under different operating conditions. Thanks to their flexible membrane, these couplings are able to transmit torque even in the moment of misalignment of the connected shafts. However, too much misalignment is one of their most common causes of failure. For this reason, it is necessary to define the critical areas of the coupling during the design and to reduce these areas with the right optimization. For this purpose, a geometric and subsequently a numerical model of the membrane coupling for simulations using FEM software Ansys Workbench is created. At the beginning, the initial shape of the membrane is determined and according to the results of individual simulations, the shape is gradually optimized. At the end of the thesis, based on the distribution of equivalent stress in the membrane, the results of individual optimizations are compared and evaluated.
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Vibrodiagnostics of electrical machines
Boháček, Daniel ; Vítek, Ondřej (referee) ; Janda, Marcel (advisor)
This thesis deals with methods of vibration analysis in electric rotating machines. From the beginning, it is necessary to explain the basic concepts and introduce the issue of vibration. Next time, the work is focused on sources of vibration in electrical machines. Defects on electric rotating machines causing vibrations are described. Sensing is performed using sensors of deflection, speed and acceleration. The measured signal needs to be adjusted and filters, approximations and sampling will cover this in the next chapter. The main objective is the methods of analysis, which include the best known in the field of frequency analysis (FFT) and the envelope method in the time domain. This includes other methods such as Kurtosis factor, Crest factor, etc. There is also a basic block diagram for measuring vibrations. This block diagram is programmed and has a graphical user interface. The last part is an evaluation of the measured data of the engines.
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