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The role of lubricants in sheet metal forming
Čvanda, Petr ; Novotný, Karel (referee) ; Peterková, Eva (advisor)
This project which was elaborated in the bachelor education present summary of lubricants in technology of forming. Annotation was based on belles-lettres of problematic of these lubricants in technology of forming and include individual sorts of lubricants and their applications in variety of forming operations
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HEAT – MECHANICAL DEGRADATION OF SURFACES AT THE HIGH TEMPERATURES
Zahradník, Radek ; Hajduk, Daniel (referee) ; Čecho, Ladislav (referee) ; Toman,, Zdeněk (referee) ; Raudenský, Miroslav (advisor)
The Ph.D. thesis is focused on a surface degradation mechanisms under combined heat and mechanical load. The objects of examination are work rolls from hot rolling mill which suffer such a load. In first chapter, the hot rolling process, the design, the manufacturing process and present materials of work rolls are described. The state-of-the-art study of work roll surface degradation mechanisms – wear, oxidation, thermal and contact fatigue are described in the second chapter. The characterization, the formation, the mechanisms of progression and the effects of each surface degradation mechanism is described step by step. The state-of-the-art study of analytical and numerical models which are related to hot rolling process is described in third chapter together with their limitations and flaws. The next chapters contain design of an analytical, an optimized macroscopic and a microscopic model for study of the work roll stress state. The macroscopic and the microscopic model is based on finite element method and they are implemented in ANSYS Programming Design Language. The models are used to process several case study which are based on previous experimental work of the Heat transfer and fluid flow laboratory. The results from case studies specify and expand the knowledge of work roll stress state. The results show the portion of each loading factor on the whole stress state. In addition, time and depth depended distribution of stress state is presented. The results from macrosferic model illustrate the cause of spalling and a rupture of the work roll. The results from the microsferic model show the cause of creation of the to-surface-parallel cracks within carbides of high chromium irons. Last chapter summarized of all results gathered from case studies together with the goals for further research definition. The necessary steps for further cognition are stated. The thesis contains a large set of appendixes with deeper discussion of several related topics. These appendixes represent the one third of whole the thesis.
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Aging and possibilities of its removal
Kolena, Robert ; Šlais, Miroslav (referee) ; Podaný, Kamil (advisor)
Thesis elaborates on current study of aging issues and describes its development caused by interstitial nitrogen and carbon atoms. It also points out how properties of materials are influenced. There are several removal options. The first one is heat treatment consisting of recovery and recrystallization annealing, the second one is binding of nitrogen atoms to chemical elements with higher affinity and third one is rolling with realization of small plastic deformation. Overall assessment and practical examples are also added.
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Vibration diagnostics of bearings
Navrátil, Pavel ; Mazal, Pavel (referee) ; Klapka, Milan (advisor)
This bachelor’s thesis introduces the basic principles of vibrodiagnostic methods and their importance for individual fase of bearing’s damage. The selected methods studied are: acoustic emission, SPM (shock pulse method), SEE (spectral emission energy), envelope method, High frequency emission, Crest factor, Kurtosis factor and special method for slow-motion machines Adash Compressed Time.
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Technology for bending unsymetric profile of steel
Walach, Lukáš ; Matušková, Jarmila (referee) ; Dvořák, Milan (advisor)
The present thesis deals with the determination of procedural parameters of given bending profile including the calculation of spring-back, especially the bending force. It compares the differences and the benefits of two different technologies of producing a blank, the simple bending and the technology of rolling. The technological process suggested involves technical-economical evaluation, supplemented with the drawing documentation.
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Boundary Conditions in the Roll Gap during Hot and Cold Rolling
Luks, Tomáš ; Pernis,, Rudolf (referee) ; Hajduk, Daniel (referee) ; Horský, Jaroslav (advisor)
Boundary conditions in the roll gap play an important role in modelling of rolling processes. In the roll gap we can observe the following: changes of rolling pressure, changes of relative velocity, influences of oxides and lubrication, etc. When taking into account all conditions mentioned above the determination of the boundary conditions is not trivial and extensive measurements are necessary. Therefore, this thesis is dealing with design of temperature and force sensors specified for the determination of friction coefficient and heat transfer coefficient in contact. The temperature sensor with an installed thermocouple measures subsurface temperature for a given depth; and then the inverse heat conduction task is used to compute temperature and heat flux on the surface. Several temperature sensors were designed and used for measuring in pilot mill and industrial rolling mill as well. The thermal responses of different sensors were compared in the numerical simulations. The inverse calculations were tested for various rolling conditions. A durability of the sensors was also studied in industrial rolling conditions. The contact stresses in the roll gap were measured by a pin, which was in direct contact with the rolled material. The forces on the top of the pin were measured by a three-axes piezoelectric force transducer and recalculated to the contact stress and friction coefficient. The sensor was implemented in a work roll and tested when rolling aluminium and steel slab for different rolling conditions. The results were compared with the integrative force sensor ROLLSURF.
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Lubricants for forming technologies
Tollrian, Zdeněk ; Císařová, Michaela (referee) ; Šlais, Miroslav (advisor)
This thesis deals with the lubricants used in metal forming technology. Requirements for lubricant, grease and selection process of forming the necessary information to determine the desired properties of the lubricant. The thesis presents an overview of lubricants that are used in various forming processes, their distribution and use. In each chapter the types of lubricants that are used in engineering practice.
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The perspectives of cold bulk forming
Garguláková, Lucie ; Podaný, Kamil (referee) ; Peterková, Eva (advisor)
This thesis deals with the processes of the technology of the cold bulk forming. Different forming methodes are introduced and described. Pictures and schemes are also parts of this work. Further on, several substance types fit for cold bulk forming are presented. This work also includes a list of companies exercising this method. Products and methodes of inovations are also named in this list. In the end, the perspective of the method of cold bulk forming along with a standing of different products at the market is evaluated.
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Study of fatigue life of roller bearings type 6204 -2Z
Poláček, Vojtěch ; Svoboda, Petr (referee) ; Klapka, Milan (advisor)
This bachelor thesis deals with the basic description of produced by fatigue failure of ball bearings. In the paper there is a description of basic diagnostic methods of machine parts. Following there is a study of vibration, their recording and the evaluation concerning bearing lifetime. The aim of the experimental part of the paper is to check the functionality and suitability od the VDT2000 analyzer and VDT Control Center software, both made by company VidiTech, s.r.o. together with the SA67 laboratory experimental stations owned by the Department of Design at Faculty of Mechanical Engineering, which were used for examining the 6204-2Z bearings. The aim of the lifespan exam is to confirm the reliability of the bearing failure warning by the analyzer and to assess the ability to record the first stages of bearing damage.
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Mechanical analysis of roof lift
Sárkány, Zoltán ; Hrstka, Miroslav (referee) ; Fuis, Vladimír (advisor)
The bachelor's thesis deals with the mechanical analysis of a roof lift in 2D, which consists of nine solid bodies. The first part of the work covers the basic necessary theoretical knowledge to solve the problem in terms of statics and dynamics. The second part of the work is the solution itself, where the equations of static equilibrium are compiled for different states of motion. Movement states where the elevator does not move at a constant speed are solved in terms of dynamics. The solution considers the effects of passive resistances. The output of the work is the resulting forces in the bonds and the assessment of the functionality of the bonds. The numerical solution was performed using the MATLAB program.
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