|
| |
|
|
Development of New Approaches in Descaling in the Continuous Production of Steel using High-Pressure Water Jet
Votavová, Helena ; Hloch,, Sergej (referee) ; Čecho, Ladislav (referee) ; Pohanka, Michal (advisor)
The thesis summarizes general and up-to-date knowledge of descaling during the continuous production of the hot-rolled steel and proposes further streamlining of this process in industrial production. The first chapter of the thesis deals with the origin, structure and physical properties of the scales. The second chapter describes the principles of descaling by using a high pressure flat water jet. The third chapter introduces the principles of the experimental methods and describes the used laboratory equipment. The fourth chapter summarizes the description of the particular experiments and their evaluation, and thus represents the focus of the dissertation. It is divided into six sections which independently solve predefined objectives of the dissertation. The first section focuses on the height and structure development of the scales on 54SiCr6 and HDT580X steels. It has been proven that the height of the formed scales increases with the time and temperature of the oxidation. The layered nature of the scales was verified at the same time. The second section examines the effect of the nozzle stabilizer on the focussing and distribution of the impact pressure of the nozzle. Experiments have shown that increase of 11 % of an average maximum nozzle pressure can be achieved, depending on the type of nozzle and the length of the stabilizer. The third section deals with the analysis of shadowgraphy images of water jet structures of the nozzles. A script was developed for analysis of these shadowgraphy photos by an adaptive thresholding. The findings are correlated using a regression analysis with an average heat transfer coefficient. It has been reported that most of the standard nozzle configurations produced disintegrated stream of little droplets at the height of the rolled surface. The fourth section focuses on the area of water jet overlap, especially the area of the so-called washout, where the impact pressure of one nozzle is reduced by the nozzle stream of the other. The influence of the pressure change and the mutual displacement of the nozzles is investigated. The analysis showed that the change of pressure did not have any effect on the percentage of reduction of the impact pressure in the area of the washout. It has been shown that if the area of the washout is wide the descaling efficiency in this area may be reduced. The fifth section builds on the previous section and focuses directly on the areas of waterjet overlaps. The influence of the change of rotation and pitch of the nozzles is studied. Experiments have shown that small changes in nozzle pitch do not have a significant impact on impact pressure and heat transfer coefficient. The effect of nozzle rotation, on the other hand, was a significant factor for the efficiency and homogeneity of the descaling of the surface. The last section deals with the effect of the rolling speed on the heat transfer coefficient in the descaling process. The regression model has shown that with a higher rolling speed there is a reduction in the average heat transfer coefficient. Conclusion summarizes the results of the dissertation and proposes which findings can be used in the industry to make the descaling process more effective.
|
|
|
Process parameters development for copper thin walls manufacturing via 3D printing
Klimek, Ľubomír ; Hutař, Pavel (referee) ; Paloušek, David (advisor)
In the work is used the processing of metallic material by the method of Selective Laser Melting. The main objective is to verify and describe the influence of the individual process parameters entering the production process when processing the alloy Cu7.2Ni1.8Si1Cr with SLM. This alloy contains 90 % copper. The first theoretical part of the thesis describes so far processed copper alloys with a high content of copper using the method of Selective Laser Melting. The practical part then deals with the specification of the main process parameters, which are optimized in the next part of the work solution. On the basis of the information obtained experimental bodies have been created, which will be tested and analyzed in several steps. The work focuses on thin-walled samples, which have a perspective use in the creation of highefficiency heat exchangers. The main results that the work deals with are the relative density and mechanical properties of the material. Also, great emphasis is placed on the resulting surface quality
|
|
| |
|
|
Process fluids in machining operations
Vondra, Róbert ; Osička, Karel (referee) ; Kalivoda, Milan (advisor)
This bachelor thesis deals with a process fluids. The first part of the thesis characterizes the fundamentals of machine cutting with the use of the process liquids. Further, there are described the functions of the process fluids and the individual technological requirements placed on the liquids, along with their advantages and disadvantages. The following chapter deals with a specific range of process fluid manufacturers in the world. At the end of this thesis, a use of process fluid in practice is illustrated. CNC grinding machine was used, in order to machine the spiral shape of a micro mill.
|
|
| |
|
|
Pilový kotouč v procesu podélného řezání materiálů na bázi dřeva
Veselý, Přemysl
In this dissertation thesis there is listed characteristics of circular saw blades, their distribution, influence of construction adjustments on final behavior of blade in the process of machining, problematic of oscillation of blades a mutual interaction among quality of machined surface, noise and dust. The thesis covers the problems of oscillation of circular saw blades as when idling and operating - the cutting process; and by the use of three circular saw blades with different construction modifications. These aforementioned construction measures are also compared to each other due to the implementation of standard construction saw blades not only from the perspective of oscillation, but also from the perspective of the roughness of the machined surface and the analysis of wood waste generated during cutting and noise. In the theoretical part there is an analysis of available literature and scientific theses. It outlines the particular publications devoted to methods of determining the shapes of oscillation, determining critical, resonant and recommended speed, blade constructions, including possible modifications, the theory of cutting saw blades including determining the size and shape of the splints and the effects of noise on the work environment. An important part of this work is methodology involving direct measurements for detection of unstable states of discs (resonance and critical speed. In this section it is further evaluated measuring of the oscillation of the test saw blade and verification of the proposed methodology with a different and practiced, commonly known method, so called cold shapes: The author also seeks to explore and determine the effect of different tooth pitch and method of execution of slots along with soundproofing grooves on noise levels, the resulting quality of the machined surface of various wood. The generated waste is then analyzed for splitting wood particles in particular size group with the percentage of each chip. The results of the experiment are in discussion confronted with the available scientific theses, taking into account with normal operating conditions, of which the conclusion is drawn.
|
|
|
Production of Special Spacer using WJM/AWJ
Novotný, Adam ; Osička, Karel (referee) ; Kalivoda, Milan (advisor)
This thesis on subject "Production of Special Spacer using WJM/AWJ" deals with the problem of progressive advanced technology, nonconventional water jet cutting, describes the process of cutting samples by AWJ technology in engineering company and discusses the effect of selected cutting program on quality of machined surface and dimensional accuracy. An attention is devoted to the substitutability of WJM/AWJ cutting methods and the possibility of combination with conventional technologies.
|
|
|
Surface changes based on FDM printing parameters
Čada, Jiří ; Sliwková, Petra (referee) ; Zemčík, Oskar (advisor)
This thesis deals with a construction of modified RepRap 3D printer Rebel II which operates with Fused Deposition Modeling technology and selection of suitable criterion for printing. It mainly focuses on the temperature of the material being printed and speed of printing for three selected materials. Materials were selected based on availability in the market and their application. An experiment, focusing on surface changes of products as well as on the look of a fibre after passing through a nozzle, was performed.
|
|
|
MODERN TECHNOLOGIES IN WIRE ELECTRICAL DISCHARGE MACHINING THE METAL ALLOYS
Mouralová, Kateřina ; Karpíšek, Zdeněk (referee) ; Pokorný, Peter (referee) ; Píška, Miroslav (advisor)
The dissertation is focused on streamlining production on wire electric discharge machine during cutting metal alloys, specifically low-alloy steel quality by CSN 41 4220. The first part contains a study of the current and modern technologies EDM wire cutting. The second part is focused on identifying key parameters to influence the WEDM process, a detailed analysis of the machined surfaces of samples and wire electrodes used for cutting. The result of this work was to explore the possibility, whether by performing planned experiment and subsequent evaluation in the future to determine exactly setting the key parameters influencing the process of WEDM.
|
guest ::
