National Repository of Grey Literature 81 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Analysis of mechanical properties of orthopedic insoles made by 3D printing
Rosický, Michael ; Halabuk, Dávid (referee) ; Návrat, Tomáš (advisor)
This thesis focuses on the influence of ribs with respect to torsional and bending stiffness in 3D printed foot orthotics. The solution is obtained experimentally by using self-made test devices and by using the finite element method. These FEM models are then extended into stress analysis. Three different designs are used for comparison, and the most suitable design is recommended at the end.
Passive Safety Features Implementation into Recovery Systems for General Aviation Airplanes
Hájek, Tomáš ; Slavík,, Svatomír (referee) ; Návrat, Tomáš (referee) ; Jebáček, Ivo (advisor)
The thesis is developed in the context of the continuous improvement of safety in personal aviation. The work focuses mainly on small aircrafts, collectively referred to as General Aviation. This thesis aims to evaluate the feasibility of implementing a passive safety feature in the form of an under-fuselage airbag in the rescue systems of small aircraft. The implementation of such a feature will help to reduce the loads transferred to the crew during a rescue parachute landing and effectively reduce the minimum altitude of the ballistic rescue system. This is a new state-of-the-art solution that is unparalleled in its category. The thesis presents a theoretical framework for solving the problem of shock absorption by airbags in the form of a mathematical model. Subsequently, the thesis presents the validation of the mathematical model based on a set of experimental data obtained for this purpose. The theoretical and practical part of the thesis then deals with the elements that influence the airbag performance, namely actively controlled air vent. The last part of the thesis performs a practical design of the implementation of the under-fuselage airbag in the rescue system of a given aircraft in terms of size, location, activation and filling of the airbag. The proposed system is capable of attenuating the impact of the aircraft from a speed of 15 ms-1, thus reducing the application altitude by 10 %. The weight of the newly designed system is equal to 5 % of the total take-off weight. The contribution of the work lies in the combination of two fields of safety that have not been addressed in this category so far, with the distinct result of improving the safety of small aircraft equipped with a ballistic rescue system.
Stress-strain analysis of the process of continuous steel casting
Cabaj, Gabriel ; Petruška, Jindřich (referee) ; Návrat, Tomáš (advisor)
The thesis is focused on the development of a computational model for determination of stress and strain of a round billet in the process of continuous steel casting. The supplied material characteristics, the geometry of the continuous casting machine and the temperature distribution in the billet are applied as input data for stress and strain analysis. The computational model based on the finite element method is developed in the commercial software ANSYS. The thesis can be divided into three parts. The first part includes background information related to the continuous casting of steel and a research analysis of the computational modeling of this process. The second part describes the development of the planar and three-dimensional computational model in detail. Finally, the obtained stress and strain results are analyzed and general conclusions, and recommendations for further development are proposed.
Application of the DIC method in the analysis of human movement
Vogel, Arnošt ; Boháč, Petr (referee) ; Návrat, Tomáš (advisor)
This bachelor's thesis investigates the potential of using the DIC method for human motion analysis. The research section provides a description of the Digital Image Correlation technique in both 2D and 3D. Moreover, existing methods for analyzing human motion in the field of biomechanics are presented. The practical part of the thesis consists of three initial experiments, where only a few points on the human body were observed. This is followed by a final experiment that examines a more extensive field of points using the DIC method.
Determination of residual stresses from strain field around drilled hole
Horák, Richard ; Návrat, Tomáš (referee) ; Halabuk, Dávid (advisor)
The master’s thesis focuses on determining homogeneous residual stresses using the hole-drilling method. The optical method of digital image correlation (DIC) is used for measuring released strains. In order to evaluate residual stresses using the entire strain field, it is necessary to know the functional dependencies of calibration constants on this field. Therefore, a significant part of the master’s thesis includes finding these dependencies in relation to the dimensions of the drilled hole and coordinates of the measured points. Another part of the thesis deals with the evaluation of homogeneous residual stresses based on provided experimental data obtained from the measurement of uniaxially loaded steel flat bar with a through-hole. At the end of the thesis, a sensitivity analysis is performed, which examines the influence of input variables in the calculation algorithm in relation to computed residual stresses.
Scanning and evaluation of a patient's hand with Dupuytren's contracture
Dalecký, Jan ; Vosynek, Petr (referee) ; Návrat, Tomáš (advisor)
This bachelor’s thesis deals with development of methodology for determining the angles between joints of the fingers of a patient with Dupyutren’s disease. The methodology works with 3D scan of the hand created with the help of a smartphone and rotating mechanism. Nowadays, the measurement is carried out with the help of a goniometer. However, this measurement is often inaccurate and may not be very pleasant for the patient. The main reason for the research is to improve the quality of the measurement results and evaluate the patient’s condition outside of the time spent in the clinic. An electronic database with the possibility of visual comparison of the patient’s conditions is also an advantage. The angle measurement process takes place on the computer in Fusion 360 and Blender software. Both measurement software and mobile scanning applications are selected to make this methodology as accessible as possible. All applications are freely accessible and user-friendly. The digitally measured values significantly match the real values and even give more relevant results for the evaluation of the severity of the patient’s condition.
Development of Algorithm for Computational Modelling of Pivoted-Pad Journal Bearings
Pokorný, Jan ; Křupka, Ivan (referee) ; Šimek,, Jiří (referee) ; Návrat, Tomáš (advisor)
The presented work deals with the calculation of stiffness and damping coefficients of hydrodynamic tilting-pad journal bearings. For this reason, a computational model of static and dynamic characteristics of these bearings is developed. The calculation is based on the solution of the generalized Reynolds equation simultaneously with the 2D energy equation for both the lubricant film and the pads. As a result, the changes in viscosity and density of the lubricant across the film thickness can be considered. The effect of turbulence is reflected by correction factors. Other influences, such as lubricant mixing, deformation and tilting of the pads, are also included in the calculation. The numerical solution using the finite volume method is programmed in Python. The static equilibrium position of the bearing is found by the efficient bounded Anderson method, which was chosen after comparison with other selected methods. Based on the equilibrium position of the bearing, the stiffness and damping are calculated using the central difference method with the inclusion of flexibility of the pivots. The results of static and dynamic characteristics of the bearing of the selected parameters are presented. Furthermore, the obtained results of the calculations are verified with experimental data taken from the literature and also with in-house measurements. A good agreement between calculations and experiments has been achieved.
Stress-strain Analysis of Carotid Arteries with Atheroma
Lisický, Ondřej ; Návrat, Tomáš (referee) ; Vimmr, Jan (referee) ; Burša, Jiří (advisor)
Kardiovaskulární příhody byly a jsou rozšířenou příčinou úmrtí ve většině zemí. Ateroskleróza karotických tepen mnohdy vedoucí k mrtvici je jejich nedílnou součástí. Včasná a vhodně mířená diagnostika rizikových lézí může vést ke snížení kritických příhod, a tím potenciálně snížit počet úmrtí. Porušení nestabilního aterosklerotického plátu je ovlivněno působením sil od proudící krve. V biomechanice měkkých tkání je využíváno výpočtového modelování jakožto potenciálního ukazatele, díky němuž by bylo možné odhalit nestabilitu plátu u pacientů podstupujících pravidelná kontrolní měření. Mechanické veličiny bývají spojovány s klinicky dostupnými ukazateli jako jsou například podstatné rozměry léze nebo přítomnost rizikových komponent. Komplexita a malé rozměry tkáně ovšem stále omezují možnosti tvorby výpočtových modelů a existuje tedy spousta faktorů, které je před možnou implementací do klinických postupů potřeba řádně vyšetřit. Tato práce je členěna do kapitol shrnujících aktuální stav řešené problematiky. Kapitoly jsou doplněny o komentář autorova příspěvku k dané problematice a odkaz na originální práci. Studium problematiky naznačilo velké množství potenciálních směrů výzkumu, což by ovšem nebylo možné zahrnout do jediné práce. Řešená témata se dají rozdělit na: (i) ověření možnosti tvorby 3D výpočtového modelu ze snímků aterosklerotického plátu s následným rozšířením na výpočtovou studii zahrnující řadu faktorů pro ověření vlivu na napjatost, (ii) studium mechanických vlastností aterosklerotických plátů odebíraných z endarterektomie během celé doby řešení, (iii) možnosti analýzy deformačního pole u experimentů zahrnujících měkké tkáně a (iv) experimentální a výpočtovou studii zbytkové deformace, potažmo napětí v souvislosti s karotickými tepnami. Výsledky jednotlivých částí jednoznačně poukázaly na problémy spojené s výpočtovým modelováním jako například časté opomíjení přítomnosti komponent stěny tepny při modelování aterosklerotického plátu, nutnost správného pochopení mechanického chování, ale také na způsob vyhodnocení experimentů s vyšším počtem vzorků. V neposlední řadě bylo ukázáno, že zbytkové napětí nemusí být podstatným faktorem u aterosklerotických plátů karotických tepen.
Numerical simulation of the hole drilling method for residual stress measurement
Halabuk, Dávid ; Ganev, Nikolaj (referee) ; Pástor,, Miroslav (referee) ; Návrat, Tomáš (advisor)
The doctoral thesis is focused on the investigation of various cases that may occur in the measurement of residual stresses by hole-drilling method and which deviate from the ideal state for which hole-drilling method is derived. In order to assess various stress states, geometries or material properties of the measured body, a computational model simulating the hole-drilling method was created by the finite element method. The first investigated case deals with cylindrical bodies and errors that may occur when the hole-drilling method is used to measure residual stresses in bodies with various surface radii. In addition to the evaluation of errors for different stress states, a procedure for the calculation of uniform residual stresses in cylindrical bodies has been proposed. The next part of the thesis is focused on investigating the influence of the residual stress placed in the perpendicular direction to the measured surface on the error of evaluated residual stresses located in a plane parallel to the surface of a measured body. The last and largest part of the thesis deals with cases in which plastic deformations form in the area around the drilled hole during residual stress measurement. After examining of various parameters influencing the formation of plastic deformations, a correction procedure which is capable to correct the uniform residual stresses for various hole diameters and various strain gauge rosettes independently of the stress state or material properties was proposed. The proposed correction procedure was thoroughly tested to ensure its satisfactory results. Based on the obtained results published in this thesis, it is possible to estimate the influence of various conditions deviating from the ideal case on the accuracy of the evaluated residual stresses and in some cases minimize this influence by the proposed procedures.
Finite element solution of axially loaded bars using linear element
Plucnar, Tomáš ; Návrat, Tomáš (referee) ; Vaverka, Jiří (advisor)
This bachelor thesis deals with the finite element method for axially loaded bars using linear basis functions. The theoretical part briefly describes the theory of axially loaded bars and states the individual steps that lead from the initial differential equation to a system of linear algebraic equations. A Weak formulation of the differential equation is used to derive the system. Using the theory described in the first part, an algorithm is created in Matlab, which is used to solve four problems. The results are then compared with the analytical solution and with the model in Ansys.

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