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Evaluation of stress and deformation of a bimetallic beam under changed temperature
Jurkovič, Vítězslav ; Horníková, Jana (referee) ; Burša, Jiří (advisor)
This bachelor’s thesis deals with stress-strain analysis of a selected bimetallic strip. First, a literature search is carried out on used bimetallic strips, including introduction of used materials and criteria for their selection. Next, an analytical calculation of free deformation of the strip at the chosen temperature is performed using rod assumptions. The following is a comparison with the results obtained using finite element method in the Ansys Workbench system. The analysis of the same strip with limited deformation is then performed using the finite element method. In this way, a stress analysis of the complete deformation constraint is performed first, including verification of the results using substitute of the deformation boundary by a force one. The following is a deformation analysis when the deformation is constrained by the selected valve spring with existing clearance, including the determination of the compression of spring. The outputs of this thesis are the results of the free deformation of strip at given temperature change, the analysis of the resulting stresses in strip due to the constrained deformation and the calculation of compression of valve spring at temperature changes.
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Assessment of a peristaltic pump tubing life used in medicine
Nováková, Karolína ; Burša, Jiří (referee) ; Jagoš, Jiří (advisor)
This bachelor thesis’s theoretical part deals with description of cardiopulmonary bypass and extracorporeal membrane oxygenation (ECMO) and their differences. Furthermore, the thesis’s theoretical part compares peristaltic pump and centrifugal pump and describes peristaltic pump’s principle, influence of peristaltic pump on the patient’s blood, tensions in the tubing and materials used for the tubing, number of rollers of peristaltic pump and tubing occlusion, including degree of occlusion, methods of occlusion setting and influence of occlusion angle. Independent chapter is dedicated to norms about peristaltic pumps with focus on reliability of peristaltic pump and its components. Another independent chapter summarizes actual state of tubing lifespan research. In thesis’s practical part, draft of tubing lifespan testing depending on the degree of occlusion and draft and execution of guaranteed tubing lifespan is described. Draft of component keeping tubing in working space is also described in thesis’s practical part.
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Evaluation of directions of collagen fibres in arterial wall and their impact on its stress-strain states
Heidrová, Aneta ; Marcián, Petr (referee) ; Burša, Jiří (advisor)
The diploma thesis deals with the evaluation of the directional arrangement of collagen fibres in the common carotid artery and their influence on its stress and deformation. The first part of the thesis, literature search, contains a description of the arterial wall, a review of some hyperelastic constitutive models used for its modelling and a summary of the current state of knowledge in the field of methods used for the investigation of collagen organisation in carotid arteries. The second, experimental, part of the paper presents results obtained from measurements of collagen orientation in human common carotid arteries, which were obtained by the author using polarized light microscopy and an automated algorithm. From the measured data, it is clear that there is one family of circumferentially oriented fibres in the artery wall, which disproves the acknowledged hypothesis of two symmetric families reported in the world literature. The subject of the third part of the thesis was the approximation of the curves during the equibiaxial tensile testing of the carotid artery using the Yeoh model and modified HGO and GOH models, in which the isotropic part formed by the Neo-Hooke model was replaced by the three-parameter Yeoh model, which is able to describe the tissue stiffening. The last, computational, part of the work uses the constants describing the used constitutive models and the structural parameters obtained from microscopic measurements to create a model of material, which was then used to simulate an artery loaded with mean arterial pressure and elevated systolic pressure at two magnitudes of axial prestrain typical of different age groups. The implementation of circumferentially oriented fibres in the computational model reduces the overall deformation of the artery, increases the circumferential and reduces the axial stress.
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Stress and strain analysis of ulna bone with plate
Šafran, Jindřich ; Burša, Jiří (referee) ; Marcián, Petr (advisor)
A fracture of the elbow joint represents a serious pathological injury. In simple cases, if it is~possible the injury can be treated without invasive surgery. In the case of more complex fractures - comminuted fractures, it is necessary to have invasive surgery and the incriminated area must be reinforced with fixation splints. The present study focuses on~performing a~strain and stress analysis of the proximal ulna, which is fixed with~a~specialized titanium splint. To assess the mechanical interaction between the elements of the system computational modelling using the finite element method was used. In the first part of the study, the orthotic investigation is focused on types of ulna fracture, including its fixation, which is complemented by an anatomical search. In the second part of the thesis, the emphasis is placed on the creation of a geometry model from the received CT data, including its~modification for the creation of a computational model. Based on the available search material models were selected or calculated. In the third part of~the~thesis, the focus is on the complex development of the computational model, including constraints, placement of muscle tendons and it also focuses on the description and consideration of the choice of computational model options. In the results presentation the effects of the identified variants of the computational model were assessed as a function of load and the strain and stress characteristics were plotted. The assessment also emphasized on the mechanical interaction between the~mechanical elements of the fixation splint and screws with the bone tissue.
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Creation of a program code for evaluation and display of inner resultants in beams
Kupka, Jiří ; Horníková, Jana (referee) ; Burša, Jiří (advisor)
The work is aimed at solution of problem with evaluating the values and courses of resulting inner effects. The goal is to algorithmize the calculation and its graphic interpretation. The main mphasis was on the correctness of numerical results and their correct depiction. Integral approach of olution and its logorithmization was chosen as suitable calculating model for given task. The algorithmus of the program itself was written in programming language C++. Thereinafter the basis of the sphere of tress and strain analysis in beams, the knowledge of which is neccessary for the given solution of the roblem or it is presumed.
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Stress-Strain Analysis of Aortic Aneurysms
Polzer, Stanislav ; Holeček, Miroslav (referee) ; Horný, Lukáš (referee) ; Burša, Jiří (advisor)
Tato práce se zabývá problematikou aneurysmat břišní aorty a možností využít konečnoprvkovou deformačně-napěťovou analýzu těchto aneurysmat ke stanovení rizika ruptury. První část práce je věnována úvodu do problematiky, popisu kardiovaskulární soustavy člověka s důrazem na abdominální aortu, anatomii, fyziologii a patologii stěny tepny s důrazem na procesy vedoucí ke vzniku aneurysmatu. Dále se práce věnuje rizikovým faktorům přispívajících ke vzniku aneurysmat spolu s analýzou současných klinických postupů ke stanovení rizika ruptury spolu se srovnáním navrhovaného kritéria maximálního napětí. Dominantní část této disertace je věnována identifikaci faktorů ovlivňujících napjatost a deformaci stěny aneurysmatu spolu s návrhem nových postupů, prezentací vlastních poznatků vedoucích ke zpřesnění určení rizika ruptury pomocí deformačně- napěťové analýzy a metody konečných prvků. Nejprve je analyzován vliv geometrie, vedoucí k závěru, že je nezbytné používání individuálních geometrií pacienta. Dále je pozornost zaměřena na odbočující tepny, které ve stěně působí jako koncentrátor napětí a mohou tedy ovlivňovat napjatost v ní. Jako další podstatný faktor byl identifikován vliv nezatížené geometrie a bylo napsáno makro pro její nalezení, které bylo opět zahrnuto jako standardní součást do výpočtového modelu. Mechanické vlastnosti jak stěny aneurysmatu, tak intraluminálního trombu jsou experimentálně testovány pomocí dvouosých zkoušek. Také je zde analyzován vliv modelu materiálu, kde je ukázáno, že srovnávání maximálních napětí u jednotlivých modelů materiálu není vhodné díky zcela rozdílným gradientům napětí ve stěně aneurysmatu. Dále je zdůrazněna potřeba znalosti distribuce kolagenních vláken ve stěně a navržen program k jejímu získání. Intraluminální trombus je analyzován ve dvou souvislostech. Jednak je ukázán vliv jeho ruptury na napětí ve stěně a jednak je analyzován vliv jeho poroelastické struktury na totéž. Posledním identifikovaným podstatným faktorem je zbytková napjatost ve stěně. Její významnost je demonstrována na několika aneurysmatech a i tato je zahrnuta jako integrální součást do našeho výpočtového modelu.Na závěr jsou pak navrženy další možné směry výzkumu.
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Analysis of residual stresses in arterial wall
Novák, Kamil ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
This thesis deals with computational modeling of the influence of residual stresses in idealized geometry of blood vessels and subsequent application of acquired knowledge to abdominal aortic aneurysm. In the terms of quality of the computational model, we reduced the uncertainties that are included in the computational model without considering the influence of residual stresses. The basic assumption of homogenization significant peaks of the stress between inner and outer vessel wall was met for each level of the computational model Methods that have been used are: deformation method (opening angle method), inverse mechanics of large deformations, fictitious temperature – for linear elastic material and hyperelastic material defined by the constitutive model. Numerical verification was carried out using program ANSYS.
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Analysis of biotribological properties of artificial hip joint
Laštůvka, Jan ; Burša, Jiří (referee) ; Návrat, Tomáš (advisor)
The development of total hip arthroplasty has reached a state when quality prostheses are made, whose longevity is influenced significantly by material properties, design, component fixation and rate of wear of the articulating surfaces. It is the wear rate which is the most important factor influencing successful results for the use of total hip prostheses. The aim of this thesis is to perform a research on the various combinations of hip prostheses and its loading conditions. Also an experimental measurements of Bovine serum lubricating film thickness between the artificial femoral head and a glass disc are performed for different contact kinematic conditions.
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