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Description of the residual stresses in polymer pipes
Poduška, Jan ; Majer, Zdeněk (referee) ; Hutař, Pavel (advisor)
This thesis is dealing with the issue of residual stress present in the wall of a polymer pipe and the influence on its lifetime. Experimental data obtained by the ring slitting method are evaluated and the tangential residual stress in the wall of polypropylene pipe is determined. The evaluation is carried out using a new methodology based on the curved beam theory. The method is verified using numerical simulation. 3D numerical model is used to verify the behavior of the pipe, when there are both tangential and axial residual stresses present in the pipe wall, because the presence of axial stress causes a rise in the magnitude of tangential residual stress. A correction of the tangential stress values corresponding to the pipe length is then proposed. It is shown, that the distribution of the tangential residual stress does not depend significantly on the dimensions or ma-terial of the extruded pipe and a general equation is proposed to describe the distribution. This general distribution is then involved in the calculations of the pipe lifetime that are carried out using a method based on the linear elastic fracture mechanics. A significantly lower lifetimes are obtained when taking the residual stress into account.
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Modifying profile design of the door leaf for rail vehicle
Lysák, Jan ; Hruzíková, Miroslava (referee) ; Majer, Zdeněk (advisor)
This master thesis deals with creation computional model of specific door leaf which was researched and now is provided by company named IFE-CR, a.s. Finite element method analysis is performed within the standards for load conditions during the operation. Stress-strain response should be the main factor to comparing results with experiment on real door. Based on acquired knowledge from the original model we can evaluate credibility of mechanical behavior of newly designed model which has lower profil tapered from the original 42 mm to 25,4 mm. From the results of FEM analysis of the modified profile is evaluated applicability to the real operational state. At the end is quantified material and financial savings achieved by reducing the height of profile.
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Description of Stress and Strain States at the Front of Cracks Loaded by Shear Modes
Žák, Stanislav ; Majer, Zdeněk (referee) ; Horníková, Jana (advisor)
The main goal of this work is the comparison of the size of the plastic zone at the crack tip for two analysis methods: an analytical linear method and an elastic-plastic analysis employing the Finite Element method (ANSYS software). All calculations were made for a crack loaded under pure shear modes. These types of loading are not sufficiently described in the literature. The first part of this work introduces the problem with the crack tip plastic zone using both linear and nonlinear fracture parameters. The second part is dedicated to the construction of the Finite Element model in the ANSYS software. The geometry of the samples and the loading levels were chosen to match an existing experimental test of the impact of shear modes on the crack behavior. In the third part of this thesis, the plastic zone radii for pure shear modes II and III are estimated using several methods and the results are compared. In the last part of this work, the same procedure as in the previous part is applied on a mixed-mode II+III loading. A result of this thesis is the assessment of the application limits of the linear analysis method used to estimate the size of the plastic zone at the crack tip for a specific geometry and material model.
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Stress, deformation and safety analysis of the recumbent bicycle frontal composite axle
Ondrejka, Jan ; Majer, Zdeněk (referee) ; Vrbka, Jan (advisor)
This diploma thesis deals with creation of computational model of AZUB recumbent tricycle composite axle for stress strain analysis. The thesis consists of four main parts. The first part contains introduction to the offer of full suspended tricycles from the most known manufacturers. Furthermore it contains introduction to composite materials that makes the main element of AZUB´´s suspension, and the description of the AZUB´´s front axle. In the second part there is detailed compilation of computational model for purpose of stress strain analysis of three load states. The effect of specific material and geometry parameters on axle behavior is discussed with the aim of choosing the most appropriate variant. Third part deals with the manufacturing of the front axle prototype and with tests leading to input data for numerical model and verification of computational model. Modifications and changes that lead to manufacturing of the second prototype are content of the last part. Based on this experience some recommendations for future development of the numerical axle model and the front axle suspension itself are formulated.
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Lifetime Prediction of the Welded Ribbed Generator Shaft
Ryšánek, Michal ; Pokorný, Pavel (referee) ; Majer, Zdeněk (advisor)
This master thesis deals primarily with the prediction of fatigue life of welded ribbed shaft. Recommendations taken from the International Institute of Welding (IIW) are used to express the stress values and the fatigue life. The stress values of examined place are expressed by approach of nominal stress, structural hot spot stress and effective notch stress. Results from stress-strain analysis are combined together with fatigue strength curves for prediction of the fatigue life. At the end of the analysis, the predicted fatigue life is compared with design life of welded ribbed shaft.
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Strength and lifetime analysis of the hydraulic key lock
Klíč, Jan ; Majer, Zdeněk (referee) ; Vrbka, Jan (advisor)
Theoretical part of this master thesis is focused on the theory of fatigue life. The second part deals with the assesment of static strength the closing flap in front of water turbine. Futher fatigue analysis of the closing flap is performed considering corrosive environment. The aim is to verify the required service lifetime of 50 years.
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Design of the axial dendritic suspension of steam turbine rotor blade
Vrbka, Dušan ; Majer, Zdeněk (referee) ; Dušek, Daniel (advisor)
This master thesis deals with axial dendritic suspension of steam turbine rotor blade. The initial shape of the suspension was design on the basis of available data. There was performed stress-strain analysis of this shape and most dangerous spots were picked. There were made several geometrical changes of the shape of suspension. Their affection on stress-strain responding of the suspension was examined. The best shape was chosen which was used to perform analysis of infinite life according to ASME code and due to loading low cycle fatigue analysis. According to results of low cycle fatigue analysis the maximum loading was established. At the end of this work the further steps were suggested.
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Deformation, stress and safety analysis of the recumbend frame.
Verner, Jan ; Majer, Zdeněk (referee) ; Vrbka, Jan (advisor)
This work contains deformation, stress and safety analysis of recumbent bike frame from company AZUB. After introduction about history, definition of beam and beam assumptions, computational model of the frame was made fallowed the main solution. Three load states was checked - stillnes / uniform ride, deceleration and pedalling. The third one was subjected to deeper analysis. Bending problem in defined location was solved for all states. Inner stress resultans was solved as Von Misses stress, and the safet y was calculated. The fist state was compared with FEM. A program in MATLAB was made, enabeling calculation of user- selected frame geometry and loading.
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