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Vehicle Hydropneumatic Unit
Koudelka, Roman ; Hejtmánek, Petr (referee) ; Blaťák, Ondřej (advisor)
This diploma thesis, following the bachelor's thesis, is devoted to the gas-liquid unit of a vehicle, as the central element of hydropneumatic suspension. The aim is to dimension and construct this component and integrate it together with other elements into a complex suspension system. Based on possible forms listed in the research section, regarding to current development trends, the form of the unit is chosen. The practical part begins with simulations comparing a hydropneumatic with a conventional suspension system. After solving this issue, it is possible to proceed to the dimensioning of the basic parameters of the unit and then to its construction, respecting the relevant strength calculations. The last step is to build a conceptual design of the whole hydropneumatic suspension system.
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The modal damping ratio analysis of the mechanical part using the OMA method
Sodomka, Tomáš ; Lošák, Petr (referee) ; Houfek, Lubomír (advisor)
In one of the first hours of study at the Institute of Mechanics of Bodies, Mechatronics and Biomechanics, the author of this work received three basic recommendations regarding measurement: 1) Do not measure! 2) If you measure, do not repeat the measurement!! 3) If you repeat the measurement, do not compare the measurements!!! However, this thesis boldly violates all three recommendations. In the introductory theoretical part, it briefly introduces the vibration of multi-degree of freedom damped systems and describes experimental ways of determining the modal damping. It also summarizes the Operational Modal Analysis (OMA) approach, explains the principle of the FDD method, and introduces EFDD (Enhanced Frequency Domain Decomposition) method which allows to determine not only natural frequencies and shapes as FDD does, but also modal damping of the shapes. A script in Matlab environment for processing vibrations using EFDD method is one of the thesis outputs. The script is first tested by computational model, where a model system with known damping is tested and damping is determined by the script. Subsequently, the work moves to the actual measurement of the real system - a bonded bar which is analysed by Experimental Modal Analysis and OMA, while the second variant uses commercial EFDD method (Brüel a Kjr company) and programmed script. In the conclusion of the thesis the damping results are compared to each other. The diploma thesis continues in Ing. M. Pop’s thesis – Modal Analysis Experimental Method Verification. From this work a part of measured data is taken. Specific cases of data use are always listed in the appropriate section of the text.
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Development of transaxles in automobiles
Kubiš, Vojtěch ; Kaplan, Zdeněk (referee) ; Píštěk, Václav (advisor)
This bachelor thesis is concerned of development of transaxles in automobiles. Overview of types of axles is mentioned here as well as their working principles. Attention is also given to suspension and damping with description of how it works. In this thesis are described solutions of selected cars suspensions.
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Effect of Shock Absorber on Vehicle Limits
Jurka, Adam ; Blaťák, Ondřej (referee) ; Hejtmánek, Petr (advisor)
The aim of this master’s thesis is to evaluate the effect of shock absorber on vehicle limits. At the beginning of the thesis, shock absorber properties were described. Then computational model was created and manoeuvres for shock absorber behaviour were defined. Created mathematical model is based on quarter model of a car and excitation in form of road with a random profile is an essential part of the model. This model was used for evaluation of heave. After heave analysis, shock absorber behaviour during drive was investigated. Drive conditions were defined as set of handling manoeuvres. For the drive investigation, complete multibody virtual model of racing car was used. Based on drive investigation analysis, optimal damping characteristics for each manoeuvre were found. Furthermore, each optimal characteristic was compared for different manoeuvres. Obtained results were compared. As a conclusion, compromise damping characteristic was suggested with the aim to fit the combination of all defined drive conditions. Final part of the thesis was aimed at validation of the computational model. Data measured during real drive were used as an input for this validation.
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Analysis of Smart Materials
Rašner, Martin ; Lošák, Petr (referee) ; Hadaš, Zdeněk (advisor)
The bachelor's thesis "Smart Materials Analysis" deals with the description of intelligent materials in the way of usability in technical practice. At first, the research of smart materials is carried out, which is further elaborated on a detailed description of shape memory materials. In order to investigate the functionality of the material and the description of its behaviour in terms of non-linear oscillation, a simplified model is proposed. The practical part deals with the application of passive damping of Nitinol. The solution is accomplished by modelling program MATLAB / Simulink.
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Modelling of damping devices in interaction with a structure
Kalina, Martin ; Lehký, David (referee) ; Frantík, Petr (advisor)
The aim of my master’s thesis was to create models of the damping device and observing their behavior in interaction with the structure. First was the construction separately modeled with Java application named FyDiK2D like a model with one degree of freedom. Model of construction takes form like a high, thin rod with full circular cross section. The lower part was restrained into the subsoil. The design was to verify the correct functionality of the model by comparing the analytical and numerical solutions. For capturing the precise behavior of the structure was converted to a multi-stage model. Then the pendulum damper was applied on this construction and found amplitude lies in highest point of multi-stage model. He was then replaced by tuned mass damper. By comparing these amplitudes from both dampers was found which kind of damper is efficient for multi-stage model.
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Active Damping of Electric Machines Platform
Vaške, František ; Houfek, Martin (referee) ; Vlach, Radek (advisor)
This thesis deals with a design of an experimental model of active damping of eletric machinery platform, its mathematical description and control through the use of a computer. It compares various ways of construction, their physical principles and feasibility. The thesis also contains a description of the model made and of the way it is controlled.
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Analysis of the effect of damping on the magnitude of the response during dynamic headlamp excitation
Lukáš, Jan ; Biskup, Martin (referee) ; Vosynek, Petr (advisor)
The aim of the submitted diploma thesis is the magnitude determination of the headlamp response to the dynamic excitation. Currently it is necessary to measure this response, because it is one of the assessed criteria of quality of the headlamp. When comparing results of the experimental measurement and the computational modelling, a good consensus of resonant frequencies is observed, but there are significant differences in acceleration amplitudes. The cause of this is the variable damping value. The theoretical part of the thesis deals with polymeric materials, basics of oscillation and damping. It serves to understand the mechanisms, which influence the results of the experimental measurement. The practical part is dedicated to the procedure of the computational modelling and the experimental measurement implementation. The analysis of the experimental measurement results leads to an ascertainment of nonlinearities, which influence the headlamp behaviour. The results of a sensitivity analysis of the computational modelling are used to create curves, on the basis of which the damping is estimated. The inclusion of the estimated damping into computational modelling leads to reduction of the compared differences of the acceleration amplitudes. The conclusion of the thesis contains the recommendation for the damping determination during the computational modelling of the headlamp.
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Computational modeling of radial hydrodynamic bearings for water machines
Pokorný, Jan ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The aim of this thesis is to calculate the stiffness and damping coefficients for radial hydrodynamic bearings. Cylindrical and lemon hydrodynamic bearings are considered. The solution to this problem mainly depends on the hydrodynamic pressure in the bearing. The numerical solution of the Reynolds equation is used to calculate the pressure. The effect of variable viscosity and density of the lubricant due to temperature changes is considered. The static equilibrium position of the journal centre is also solved. The stiffness and damping coefficients are determined using small amplitude journal motions about the equilibrium position. Three methods for determining these coefficients are presented. The outcome of this thesis is an algorithm for the calculation of stiffness and damping coefficients for cylindrical and lemon bearings. Results for lemon bearings are presented and comparison with the commercial software DynRot BR is made. The benefit of this thesis is the creation of an algorithm for the calculation of journal centre equilibrium position, a new way of incorporating the temperature changes in the viscosity and the density of the lubricant, and the modification of a method for calculating stiffness and damping coefficients based on experimental analogy.
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