National Repository of Grey Literature 34 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Mechanical-structural characteristics of multi-materials prepared by additive technologies
Hyspecký, Michal ; Válka, Libor (referee) ; Pantělejev, Libor (advisor)
The diploma thesis deals with the mechanical-structural characteristics of the multimaterial interface prepared by the additive cold-spray (CS) technology. In the experimental part of the work, the titanium alloy Grade 23 was applied to the surface of aluminum alloy EN AW 2618, after heat treatment T6. Furthermore, a separate bulky block made of Grade 23 alloys for the production of tensile bodies was created using the CS method. The sprays were evaluated in two planes perpendicular to each other, respectively in longitudinal and transverse section. The average porosity of the coatings was evaluated at 2,6 ± 0,6%. The hardness value at low load did not change significantly with increasing distance from the interface and the mean value was 347 ± 51 HV 0,3. The tensile test did not show a significant effect of the sample orientation on the resulting value of the yield strength, which had the diameter of 345 ± 12 MPa. Successful deposition takes place at the temperature of 1010 ° C and the pressure of 5 MPa. The achieved results of the mechanical properties of the coating determined on the basis of tensile tests are at a relatively good level. Therefore, it is possible to consider the use of coating by this method, under given conditions, for rotating components operating at elevated temperatures, and increase their efficiency or service life.
Adhezion wear mechanisms of moving engine parts
Cahová, Kristýna ; Válka, Libor (referee) ; Jan, Vít (advisor)
The thesis describes adhesion wear on a contact area between Common rail and the component and deals with various effects on this kind of wear. The aim of the thesis is to gain information about adhesion wear phenomena and to understands its physical principals. Theoretical part deals with description of Common rail and then it is focused on research of adhesion wear. Experimental part firstly summarizes available data from tests that have been already done and then continues with analysis of microstructure of materials which are in contact during assembling process and the formation of adhesion wear is increased there.
Determination of mechanical characteristics of coatings using impulse excitation technique
Valášek, Daniel ; Řehořek, Lukáš (referee) ; Válka, Libor (advisor)
This diploma thesis deals with the determination of the Young’s modulus of coatings using the impulse excitation technique (IET). The theoretical part of the thesis describes Cold and Thermal Spray technology, theoretical foundations of the impulse excitation technique and models of composite materials. The experimental part of the thesis deals with the determination of the tensile modulus of copper coating created by Cold Spray technology. The impulse excitation technique has been used to measure fifteen samples with coating thickness ranging approximately from 0,4 to 2 mm. Results from this measurement were evaluated using five composite models to establish the Young’s modulus of the applied coating. The best results were achieved by using the composite model based on rule of mixtures (ROM).
Characterisation of Cold Sprayed Stainless Steel Coating
Černý, Dominik ; Válka, Libor (referee) ; Řehořek, Lukáš (advisor)
Bachelor thesis is in the first part focused to basics of Cold spray method and parameters, which affect this method. In the eperimental part, microstructure and mechanical properties of supplieand, and also new faze formed by heat treatment, were exemined and observed.
The use of small punch tests for materials with a higher level of structural inhomogeneity
Gordiak, Michal ; Řehořek, Lukáš (referee) ; Válka, Libor (advisor)
Master's thesis deals with evaluating applicability of correlation relationships between material characteristics determined by Small Punch Test and standard tensile test for material AlSi7Mg0,6 manufactured by casting and technology SLM. Results of Small Punch Tests are correlated with yield strength, tensile strength, elongation, and Young's modulus of elasticity. For each material characteristic various correlation methods are compared, while for each method corresponding coefficients are determined. Consequently, the applicability of individual methods is evaluated by substituting coefficients determined by various studies. Primarily analyzed are correlation methods for which future normalization is expected. The results of master's thesis show that structural inhomogeneity caused by SLM process does not result in high inaccuracies in determining material characteristics. Larger impact on material characteristics has high porosity, which was identified in cast material and led to significant deviations in evaluating tensile strength and elongation.
Repairs of component contact area using Cold Spray technology
Matiash, Dmytro ; Válka, Libor (referee) ; Řehořek, Lukáš (advisor)
The aim of this master’s thesis was to evaluate cold spray technologies as an alternative method of repairing contact surfaces of parts, especially made of high-alloy manganese steels, to choose a suitable system of materials and to analyze the properties and structure of the produced coating. The thesis presents the basic of the mechanism of cold spray deposition, the described influence of basic process parameters on the structure and properties of metal coatings. Performed analysis of chemical composition, structure, porosity, hardness and strength of AISI H13 steel coating on a high-alloy manganese steel substrate. The described dependence of the structure and properties of a given coating on the heat treatment regime.
Mechanical properties of materials prepared by SLM process
Doubrava, Marek ; Válka, Libor (referee) ; Pantělejev, Libor (advisor)
The diploma thesis deals with the selection of process parameters used for manufacturing of high-strenth materials using SLM technology. The feedstock material was powder with a chemical composition according to standard DIN X3NiCoMoTi 18-9-5. Influence of change in process parameters on mechanical properties was examined by hardness tests and tensile tests. Metallographic and fractographic analysis were conducted with an aim to understand mechanisms of failure present in this type of material. Selection of optimal process parameters was based on the analysis of mechanical properties of manufactured samples. Possible future steps related to the improvement of the process were proposed. Results of this experiment were compared with literature regarding parts produced by SLM technology and conventional methods.
Mechanical properties of the weld of titanium alloy TiAl6V4 prepared by using an electron beam technology
Byrtus, Robin ; Pantělejev, Libor (referee) ; Válka, Libor (advisor)
The aim of the diploma thesis is to evaluate the mechanical properties and fracture behavior of the weld join Ti6Al4V titanium alloy prepared by using an electron beam technology. The theoretical part deals with the welding of titanium alloys with the help of electron beam, the weldability evaluation of titanium alloys, the influence of electron beam welding on the microstructure and the methods of testing of weld joints. Using the experiments, the mechanical properties of the base material and the weld were evaluated and a structural analysis of the weld was performed.
Influence of the MuCell technology parameters on the mechanical properties of polymers for injection moulding
Suchánek, Matěj ; Věchet, Stanislav (referee) ; Válka, Libor (advisor)
This master’s thesis deals with influence of gas content in structure of polymer materials to mechanical properties. Test specimens were prepared by MuCell technology from polyphthalamide reinforced by 50 % of glass fiber content. The theorethical part of this thesis is focused on polymer materials with attention to polyamides and injection moulding technology. In the experimental part, the dependence between the characteristics obtained from the tensile test and the Charpy impact test on the amount of gas in the polymer is examined.
Mechanical properties of polymers produced by 3D printing technology
Král, Filip ; Moravčík, Igor (referee) ; Válka, Libor (advisor)
The thesis deals with the dependence of mechanical characteristics on the anisotropy of polymers Nylon 12 and Ultem 9085 made by a 3D printing technology Fused Deposition Modeling (FDM). The evaluation of the material characteristics was performed on the basis of tensile and non-instrumental impact tests. It was proven that the material characteristics are strongly dependent on anisotropy, i.e. on layer thickness and raster angle for both types of polymers.

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