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Design of apparatus for determination of directions of reinforcing fibres in soft biological tissues in their deformed state
Sodomka, Tomáš ; Vaverka, Jiří (referee) ; Burša, Jiří (advisor)
The Bachelor´s thesis is focused on the determination of directions of collagen fibres in elastic arteries. The first aim of this thesis is a general introduction into soft tissue mechanics with turning attention to connective tissue where collagen fibres are their inseparable part. Also the thesis introduces arrangement of collagen fibres, their waviness and how the waviness thwarts determination of direction of fibres. The second aim is a design and test of the mechanical apparatus, which is able to stretch a squared aortic sample in two perpendicular directions (independently on each other) up to the relative deformation of 30 %. Design of the apparatus allows the sample to be dipped into the formaldehyde solution, which fixes the deformation. Consequent histologic sections of the sample will be used for the determination of global directions of collagen fibres in the aorta. The apparatus is designed to simulate conditions in a human or animal body where aorta is axially pre-stretched and at the same time expanded in the radial direction by blood pressure.
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Solution of the exact differential equation of deflection curve
Šikl, František ; Fuis, Vladimír (referee) ; Vaverka, Jiří (advisor)
This bachelor thesis deals with the deformation of a beam loaded with a basic bend using the differential equation of the deflection curve. The work is divided into four parts, where in the first part the general form of the differential equation of the deflection curve, which is based on simple geometry and mathematical approximations, is derived. In the second part, we will describe the basic methods of solving the differential equation of the deflection curve for large deformations for simple cases, where we must use the nonlinear form of the already mentioned equation. However, we will also mention methods that can be used for specific cases. In the third part, two numerical methods, which can be used to solve large deformations of beams, are being programmed. The last part describes the difference between the linear equation of the deflection curve, which is simplified and taught commonly, and the nonlinear differential equation of the second order. The fundamental task of the work is a comparison of commonly used methods to determine the deformation of the beam and to determine the degree of load, when it is possible to use a simplified differential equation of the deflection curve, and when not. However, it is important to mention that the numerical solution cannot always be used, so the example will be embedded in a simple case.
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Determination of stress resultants in closed frames
Horák, Richard ; Horníková, Jana (referee) ; Vaverka, Jiří (advisor)
The bachelor's thesis deals with the determination of the internal stress resultants (ISR) of planar beams with a closed centerline. The first part of the thesis presents a theoretical basis, which is then applied in the second part to solve three tasks. In the first task, the theory of symmetrical and antimetrical course of ISR is applied to reduce the degree of static indeterminacy of a symmetrical planar beam loaded by a symmetrical and antimetrical force system. In the second task the method of superposition is used to replace the general external load of the beam by symmetrical and antimetrical external loads. The task is further solved in the same way as in the case of the first task. The third task is solved by a general procedure with several options of released structures. Furthermore, the assumption enabling the solution of the stress energy due to the bending moment only is verified. At the end of the third task, the analytically determined values are compared with the values determined by the numerical method using the software ANSYS.
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Finite element solution of axially loaded bars using quadratic element
Janáčik, Lukáš ; Halabuk, Dávid (referee) ; Vaverka, Jiří (advisor)
This bachelor thesis describes an algorithm for programming finite-element model with quadratic elements for axial loaded bar. In the introduction, we define the basic concepts of mechanics of materials, which are used in this thesis and are necessary to understand problems, for which finite element method was formulated. The thesis clarifies a transition from basic differential equation to weak formulation, which is the base of finite element method. We define element matrices and describe transition to global matrices, relating to the whole body. Then describe implementation of boundary conditions and postprocessing of the results, necessary for calculation and displaying of other unknowns. In the practical part, 3 illustrative problems are presented and calculated numerically in FEM solver using Matlab, analytically and in software ANSYS Workbench. Results are then compared and evaluated. Problems have different boundary conditions (linear axial load, tempered cross section, statically indeterminate fixation). Results of displacement and normal stress for programmed solver are identical to those from Ansys (using the same settings) and analytical solution (after more elements are added, if necessary). Problem with tempered cross section was simulated in Ansys using plain stress, because the program can’t define bar with tempered cross section. This revealed sheer stress contained in parts of cross section further from centreline, which are not calculated in our FEM solver and in some cases might be significant.
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Technological design of a manufacturing process modernization
Vaverka, Jiří ; Dvořák, Jaromír (referee) ; Kalivoda, Milan (advisor)
The topic of this thesis is to design the modernization process. The aim of this work the design of new machines for a particular component, which would replace the existing ma-chinery used in company-tion in which the component is produced. Introduction is focused on the description of the company and selected components for which it is evaluated di-mensioning, tolerance, functionality and material. The following describes the current ma-chinery engineering company and then are selected machines in two variants, which would replace the original equipment. With these new machines is a technical documentation and is evaluated modernization and environmental concerns. At the end of the re-evaluated results that modernization is beneficial or not.
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Analysis of stresses in left ventricular wall during isovolumic contraction
Janoušek, Petr ; Burša, Jiří (referee) ; Vaverka, Jiří (advisor)
The objective of this work is the analysis of stresses in the left heart ventricle during the isovolumic-contraction phase, in which blood is compressed without changing its volume in the ventricle. In this work, the left ventricle is modeled using a simplified axisymmetric sphere in order to be able to (1) perform an analytical solution from the relations given in the literature corresponding to the theory of linear elasticity, and (2) compare this solution with the model calculated by the finite element method. The model itself is a thick-wall sphere, which is affected by an internal overpressure arised as a reaction from the compressed blood. In order to achieve a constant internal volume, an active strain which acts against the internal pressure is also considered.
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Feasibility study of welding for stainless part „ guide rail"
Vaverka, Jiří ; Mrňa, Libor (referee) ; Sigmund, Marian (advisor)
Robotization of industry is very important in these days. It is possible to replace human workers with robots and because of that make manufacturing faster. This master’s thesis includes feasibility study of robotic welding for stainless steel part guide rail. Quality of robotic welding was evaluated on testing pieces. Robotic welding was 88,5 % faster than current welding method. Costs of manufacture of one piece were 40 % cut.
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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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