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Manufacture of optical mirrors for high-frequency antenna
Muzikant, Dušan ; Bumbálek, Bohumil (referee) ; Sedlák, Josef (advisor)
This thesis deals with problems with manufacturing of high frequency elliptic and hyperbolic optic mirrors, which makes one of the most important functional parts of parabolic satellites made for biggest and highest placed international astronomical radio-telescope in the world - ALMA, which is built on Chajnantor plateau in Chille in South America. Individual chapters are designed in the flow of technological process of manufacturing, containing theoretical and practical analysis of the problems. Content of the thesis leads especially to description and clarification of individual causes of problems during manufacturing.
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Influence of residual stress on pressure vessel part fatigue life
Boleloucký, Václav ; Vincour, Dušan (referee) ; Létal, Tomáš (advisor)
This bachelor’s thesis deals with the impact of a residual stress, caused by an applied cyclic pressure, on fatigue life of a pressure vessel part (flat end–cylinder connection). Bachelor’s thesis includes the design of the pressure vessel according to CSN EN 13 445 regulations, analytical solution in Maple software, from which stresses and deformations are determined. Then the results of the analytical approach are firstly verified by a FEM modelling in ANSYS Workbench software and secondly compared to each other in graphs and discussed. From the values of stresses in FEM, analysis fatigue life expectations are calculated with the respect to CSN EN 13 445 regulations, for two cases. First one, where a pressure test is applied and second one, where the pressure test is not applied before the pressure vessel is put into service. In the conlusion the obtained results are discussed.
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Processing of Inconel 939 alloy using laser powder bed fusion at elevated temperatures
Hertl, David ; Dočekalová, Kateřina (referee) ; Malý, Martin (advisor)
The thesis deals with the problem of Inconel 939 alloy processing by SLM technology using base plate preheating. The main objective of the work is to verify the effect of base plate preheating on residual stresses. The problem was solved by two approaches: process simulation, and subsequent experimental verification. The process simulation with preheating temperature of 400 °C achieved the highest agreement with the experiment with a deviation of 4.1 %. Based on the experiment, a suitable base plate preheating temperature of 100 °C was determined to reduce the deformation and residual stresses. By processing Inconel 939 using preheating temperatures of 100 °C and 400 °C, static mechanical properties comparable to those of the standard components processed by SLM technology from Inconel 939 after the heat treatment were achieved. These results offer the potential for significant reductions in overall production time and costs associated with manufacturing Inconel 939.
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Age forming of aluminium alloys
Stanislav, Filip ; Petrásek, Miloslav (referee) ; Klement, Josef (advisor)
The diploma thesis is focused on the description and the verification of a relatively young creep age forming method. This method is based on a relaxation of stress and a creep of material, which occur by forming a part in the clamping tool during the artificial precipitation heat treatment at elevated temperature. After removing from the tool, the spring back and the residual stresses in the part are smaller compared to the conventional forming methods. This is mainly reflected in the increased fatigue resistance of the structure. The creep aging is only applicable to the precipitation heat treatable alloys. This thesis is focused on aluminium alloys, which are typical for the aerospace industry. The first part of the thesis describes principles of technology, its use in the aviation and material processes in the aluminium precipitation heat treatable alloys during the creep age forming. In the second part, there is a methodology of the verification of technology on samples made of the aluminium alloys ČSN EN AL-P 7075 and ČSN 424203 (approximate equivalent of ČSN EN AL-P 2024). Furthermore, a forming tool is designed, and experiments are performed according to the proposed methodology. At the end of the thesis, the experiments are evaluated and changes in the spring back of the samples are compared for three different methods of forming: the conventional cold clamping forming, the creep age forming and the creep age forming with an overaging.
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Determination of residual fatigue lifetime of railway axle after surface treatment
Pánek, Ondřej ; Poduška, Jan (referee) ; Náhlík, Luboš (advisor)
This master thesis deals with prediction of residual fatigue lifetime of railway axle. In the first part of this thesis, theoretical introduction to the issue based on research of available literature is elaborated. The second part is dedicated to numerical modelling of actual railway axle with crack, which serves to obtain the necessary parameters entering estimation of the residual fatigue lifetime. At first, a finite element model of cylindrical body with crack loaded by bending moment was created and compared with analytical solution for verification purposes. The second step was the creation of separate models of railway axle with crack for three types of loading – bending moment, press fit of wheel and residual stresses, respectively. Furthermore, the shape of various crack propagation stages was determined, according to the methodology developed at IPM CAS. Using the determined crack shape, stress intensity factors were calculated separately from all types of loads for various crack depths. Dependence of stress intensity factor on the crack length was then used to calculate residual fatigue life for real loading spectrum.
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The influence of geometry and cutting tool parameters on residual stress during machining of the pressure containers
Berka, Martin ; Kouřil, Karel (referee) ; Strejček, Jan (advisor)
This thesis deals with the influence of changes in cutting parameters and tool geometry on residual stress inside the material. I examine the influence by deep drilling. Changing the cutting parameters concerns the alteration of the tool feed and the pressure of the coolant during the process. The influence of tool geometry is studied by using two different single edge cannon drills. The research was realized in cooperation with Bosch Diesel Ltd. The theoretical part includes a description of the injection system, in which a high-pressure container is contained. The high-pressure container was used to evaluate the influence of the cutting parameters and tool geometry on residual stress. Furthermore, the theoretical part deals with the deep drilling technology used and the theory of residual stresses. The practical part shows the measurement parameters and the corresponding results. In the conclusion of this thesis, a technical-economic evaluation of the measurement is conducted.
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Application of DIC method in residual stress measurement using hole drilling method
Kováříková, Sabina ; Kubík, Petr (referee) ; Návrat, Tomáš (advisor)
This thesis deals with measurement of residual stress by hole drilling method. This method is based on drilling a hole and measurement of deformation in the area around this hole. Measured deformations are then converted to residual stresses by using calibration coefficients. The deformation around the drilled hole is measured by optical non contact method called digital image correlation (DIC). First part of the thesis is focused on current state of research. The thesis contains evaluation of residual stresses by using different methods and evaluation of used methods.
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Comprehesive Theoeretical Analysis of Ring-Core Method for Residual Stress Determination
Civín, Adam ; Holý, Stanislav (referee) ; Plánička, František (referee) ; Frydrýšek,, Karel (referee) ; Vlk, Miloš (advisor)
Comprehensive analysis of the ringcore method used for the determination of the residual stresses in mechanical components is presented in this thesis. Principles, advantages, disadvantages and applicability of this semidestructive experimental method are discussed too. At the same time the ringcore method is compared with the hole drilling method, which is used more frequently. All aspects of the ringcore method are analyzed by the finite element method. FE simulations, performed on the universal numerical model, verified principles of the integral method and the incremental strain method. FE simulations also provided basic information for the uncertainty analysis, which significantly affects the accuracy of the residual stress measurement. The main goal, which the present work deals with, is to create a global overview of all ringcore methods´ aspects elaborated in a clear and complex form.
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Design and realization of experimental equipment for determination of residual stress of bent samples
Novotný, Lukáš ; Návrat, Tomáš (referee) ; Krejčí, Petr (advisor)
The master thesis is focused to design and realization of experimental equipment for researching of residual stress determination for specimen with non-uniform distribution stress along the depth. Literature search study of problematic was performed and it was used for elaboration of chapters about origin of residual stress, their classification and chapters about methods, which are used for measuring of residual stress and their determination. The following part explains the design of experimental equipment and stress-strain analysis of selected parts of this equipment. Then the final design of equipment is presented, including complete production drawings, and it’s explained final assembling of experimental equipment. Final chapter is devoted to examinable loading of specimen.
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