|
|
Service life increasing of spare part tools for ground cultivation
Černín, Jiří ; Mrňa, Libor (referee) ; Sigmund, Marian (advisor)
This diploma thesis deals with increasing the service life of parts intended for soil cultivation. The work evaluates the current possibilities of increasing the utility value of spare parts. Practical tests will provide recommendations for the most appropriate method to increase durability. The work examines uncharted methods of testing soldered joint. The results are evaluated in terms of quality and economic profitability. All results from this work are based on the basis of practical tests of plowing machine in rocky soil.
|
|
|
Design of ceramic coating for disc brake of bicycle
Eliáš, Vojtěch ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This Bachelor Thesis deals with the design of ceramic coating on a braking rotor of a bicycle and its implementation. The reason for this is the achievement of better heat resistance as well as better abrasion resistance, which are typical properties of ceramic materials. The method of heat plasma spraying was employed in order to apply the coating. The coating material consisted of the binding layer made up by 95% Ni and 5% Al and of the outer (superficial) layer made up by 92 % ZrO_2 and 8 % Y_2 O_3 . After the coating had been sprayed, the rotor was tested in real conditions of a bicycle ride. Considering the absence of the necessary measuring equipment, the testing was only based on the rider's subjective feelings. The sprayed coating showed slightly worse friction properties compared to conventional steel, however, the functionality of the braking device was not significantly limited.
|
|
|
Analysis of friction welding by SFW process
Šajkovics, Patrik ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
Bachelor thesis developed in the bachelor study focuses on the analysis of friction welding by SFW process. The work is focused on a detailed description of the principle of technology SFW and its other modification. It describes the microstructure of the welds and it depends on the mechanical properties. Were summarized advantages and disadvantages, industries which the SFW used, suitable materials for welding and material of welding tools. SFW technology is focused on non-ferrous metals and their alloys, but the conclusion is also mentioned steel welding technology SFW and material of tools are suitable.
|
|
|
Optimization of a part production made of a structural 20 mm thick steel using laser cutting technology
Šoukal, Hynek ; Hála, Michal (referee) ; Mrňa, Libor (advisor)
The thesis deals with the optimization of process parameters in the oxidative laser cutting of structural 20 mm thick steel with regard to the type of material, the resulting roughness of the cut and the resulting price of the product. In line with the literary study and the Taguchi method, an experiment was developed. The cutting speed, laser performance, cutting gas pressure, and focal position were controlled during the experiment. Sample sets were cut with 7.5" and 10" focusing lens from the TATA STEEL S355MC and SSAB LASER 355 MC steels. According to ČSN EN ISO 9013, the samples were evaluated for roughness. Then micro and macro structures were evaluated, and compare the hardness according to Vickers. In conclusion, technical and economic evaluation was determined.
|
|
|
Influence of process parameters on the roughness of the cut during laser cutting of stainless steel thickness 8 mm
Shkotova, Viktoriia ; Horník, Petr (referee) ; Mrňa, Libor (advisor)
This bachelor thesis deals with optimization of process parameters of laser CNC center. An IPG YLS-5000 solid state fiber laser was used in the experimental section for separating austenitic stainless steel X5CrNi 18-10 thickness 8 mm. Within the optimization, three parameters were changed: power, scroll speed and focus position. For each, a set of 10 samples was created. The roughness measurement and subsequent classification into the tolerance classes was based on ČSN EN ISO 9013. Although the changes in power did not show a bid differences in roughness, the tendency of the surface roughness decreases with the increase in the parameter value. The best results were achieved when the focus position and speed were changed. Samples 41 and 42 have a good surface quality, but there is a burst at the bottom edge. In the real situation, additional operations would be needed to remove them. Sample 61 has the smallest roughness surface without defects, but the cutting speed was almost twice lower than in samples 41 and 42. Because production time is very important from an economic point of view, it would be necessary to calculate the time for all used operations.
|
|
|
HSS welding process automation in nuclear power plant
Charvátová, Eliška ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
The bachelor thesis compares the manual and mechanized method of welding in the production of dissimilar weld joint. The samples were welded from austenitic and ferritic-perlitic parent materials with using the same type of high alloy filler material. Joint geometry is identical for both methods. Nondestructive and destructive controls were performed, the structural changes in the materials given by the different amounts of heat transfer into the weld joint were compared. Increasing the corrosion resistance of the inner pipe surface is ensured by nickel layer.
|
|
|
The surface quality of the fused silica machined by ultrafast laser
Novotný, Jan ; Mrňa, Libor
The quality of ultrafast laser-machined surfaces depends on several process parameters. In the experiment, the parameters window that yields the lowest roughness and lowest number of defects were found. The most important parameter after laser fluence is scan line overlap, which has the biggest impact on residual heat dissipation and related stresses in the specimen. The second harmonic wavelength yielded 10 % better surface roughness, lower waviness, and a lower number of defects on the surface and edges of the processed area.
|
|
|
Hybrid laser-MIG/MAG welding at ISI
Mrňa, Libor ; Novotný, Jan ; Šebestová, Hana ; Znášik, Samuel ; Gross, Jan ; Harašta, Jiří
Laser welds usually suffer from underfill defects because the welding is usually made without a filler wire. During the hybrid laser-MIG/MAG welding, the laser beam forms the melt pool, and the arc simultaneously delivers melted filler wire. The synergic interaction of both heat sources allows deeper penetration while the weld face is sufficiently filled and has the prescribed geometry. This contribution reports the issues of individual systems integration and presents already-made experiments.
|
|
|
Beam oscillations for modification of fatique properties of laser welds
Šebestová, Hana ; Jambor, Michal ; Mrňa, Libor
The application of suitable beam oscillating parameters reduces root notches of laser welds. Beam oscillation welds reach better fatigue properties compared to conventional laser weld, even though the notches are not reduced. The welds made with linear oscillation have the highest number of cycles to fracture in the high-cycle region. However, the root notches are not eliminated in these welds because of high values of current heat input on weld peripheries. The experienced thermal cycles must be also considered. They can induce microstructural transformations and change the distribution and magnitude of residual stresses, which are the additional factors influencing the fatigue lifetime of a weld joint.
|
|
|
Hybrid laser-MIG welding of steels for the energy industry
Mrňa, Libor ; Šebestová, Hana ; Horník, Petr ; Novotný, Jan
Laser-MIG welding can lead to the heterogeneity in the weld metal. A weld root's chemical composition corresponds to the base metal, while the face is formed dominantly by the filler wire that can have a different chemical composition. The study reports on the hybrid technology of laser-MIG welding utilized for joining creep-resistant martensitic stainless steel used in the production of steam turbine components. The hybrid welding system capable of modifying laser spot diameter was developed and the welds with chemically homogeneous weld metal were achieved.
|
guest ::
