National Repository of Grey Literature 62 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Mechanical response during dynamic loading of layers prepared by cold spray technology
Šprincl, Jan ; Válka, Libor (referee) ; Řehořek, Lukáš (advisor)
Cold spray is a relatively modern technology that falls into the additive category. It is a coating method that doesn´t cause the input material to melt. This brings many advantages, including the minimization of changes to the original structure, the absence of a heat-affected zone, and the possibility of combining different types of materials. This work mainly focuses on the deposition of Ti6Al4V titanium powder, along with other materials to supplement or modify the spray, improve its efficiency, and enhance its mechanical properties. Ballistic tests, three-point bending tests, indentation methods, optical analysis using light and electron microscopy, X-ray diffraction, differential scanning calorimetry, and the influence of thermal treatment on the structure were used to evaluate the properties. Thermal treatment led to the formation of completely new phases in the structure, resulting in a significant increase in the coating's hardness along with a reduction in its porosity. Highly hard phases based on TiC and Ti5Si3 were formed in a tough matrix composed of varying ratios of Ni-Ti and associated elements – V, Al, Si. Finally, proposals for potential future development of this material are described. Preconditions for specific improvements in the methods and procedures used in this work are laid out, with a very promising outlook for the future of this material and its potential implementation in real ballistic protection, typically in the military industry.
Design of powder preheating for cold spray technology
Kalina, Jan ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
Cold spray is a technology that ranks among the thermal coatings. Its main idea is to prevent both the sprayed and the underlying material from reaching the melting temperature in order to reduce the level of surface oxidation. Cold spray is a relatively young technology that is still being researched. The effect of preheating the sprayed material on the material characteristics of the cold spray is one of the research questions. As part of this work, a device for preheating the powder to temperatures of up to 650 °C is designed in such a way as to minimize interference with the current construction of the Cold Spray workstation at the ÚMVI FSI BUT in Brno. The design is based on significant simplifications of the thermal model of the preheating device and heat losses. In the theoretical part, the reader was introduced to the history of Cold Spray, the effects of various technological parameters of Cold Spray on the resulting spray. Furthermore, the requirements for the preheater device were discussed, several variants of the device design were proposed, and the equations used for the device design were written. In the practical part, the required data for the design of the equipment is obtained for the required materials of the sprayed material, different temperatures, and other input parameters of the Cold Spray injection with the help of equations from the theoretical part. Based on them, the final design of the preheater device is compiled.
Elastic characteristics of coatings
Olivo, Tomas ; Řehořek, Lukáš (referee) ; Válka, Libor (advisor)
The thesis focuses on the determination of Young's modulus of elasticity in tension of coatings with the inclusion of the effect of porosity using the impulse excitation method (IEM). In the theoretical part, the basics of the impulse excitation method and nanoindentation are discussed. Subsequently, the types of composite materials are presented, followed by a description of the Cold Spray technology used to produce the coatings presented in this work. In the next section, the composite models used to evaluate the measured data are defined. The experimental part is devoted to the description of the preparation of the test specimens, i.e., the substrate-coating system, together with the nanoindentation and pulsed excitation test procedure. Based on these tests, the tensile elastic moduli of the deposited coatings were evaluated using four composite models and compared with the results from the nanoindentation test. The most appropriate of these models was found to be the one based on the rule of mixtures with the inclusion of the nonlinear effect of porosity.
Utilization of cold spray technology for ballistic applications
Kuník, Adam ; Doubrava, Marek (referee) ; Řehořek, Lukáš (advisor)
The goal of this bachelor's thesis is to get familiar with cold spray technology, as an alternative in the field of both coating application and, among other things, its use for the repair of some parts with complex shapes within additive manufacturing. It then coveres the basic principles of this method, the metal powders used, the characteristics of the device, familiarization with the issue of ballistic protection and terminal ballistics. In the second, experimental part, the quality and mechanical properties (especially the hardness, porosity, and coating thickness) of this layer produced by the above-mentioned method, as part of ballistic protection for light armored vehicles, are evaluated.
Development of Ti-6Al-4V alloy coatings produced by cold spray technology
Ballayová, Kristýna ; Štěpánek, Roman (referee) ; Řehořek, Lukáš (advisor)
The cold spray method is receiving more and more attention both in research and development and in the industrial sector due to its undeniable advantages over conventional methods. However, the suitability of its application depends on the desired properties of the coating and the nature of the materials used. This work provides insight into cold spray in general and in the context of the spray material used – Ti-6Al-4V. The response to several sets of hot isostatic pressing (HIP) parameters was studied, with attention paid not only to the coating but also to the Al 2618 aluminium alloy substrate. The choice of hot isostatic pressing parameters, especially temperature, was a compromise solution with respect to the temperature resistance of the substrate material and the common values of this process in the processing of the spray material. The results of the practical analyses show that despite the efforts to find HIP parameters satisfying both constraints, the most essential properties of the coating were not improved. On the contrary, the HIP process led to a certain deterioration of the properties of the aluminium alloy substrate. These findings provide information for future process optimization and highlight the need for further research into the combination of these materials and technologies.
Surface modification of titanium alloy metal parts made by SLM technique
Lacová, Anna ; Řehořek, Lukáš (referee) ; Jan, Vít (advisor)
Electrochemical Polishing, Titanium alloys, SLM, Surface Modification
Press quenching of HEMA sword blades
Achberger, Šimon ; Řehořek, Lukáš (referee) ; Kouřil, Miloslav (advisor)
Martensitic transformation during quenching is inherently related to creation of residual stresses within the quenched part, which lead to quenching-induced distortion. There are multible approaches to reducing quenching-induced distortion. Among the more effective is utilising cold die quenching. Construction of a cold die quench press for quenching thin, flat parts is relatively simple, but scarcely used due to high investment costs and the difficulty of determining thermal contact conductance between quench press dies and quenched part. An example of a part whose manufacture is complicated because of quenching-induced distortion is a sword blade. The experimental part of this thesis examines quenching samples of a steel used for making sword blades, 42CrMo4, using two different quench press die constructions. Analysis of said samples shows that proposed quenching method is comparable or superior to quenching via conventional quenchants. Proposed quenching method lowers quenching-induced distortion and has minimal recurring costs connected to using liquid quenchants and the method is therefore viable for quenching sword blades.
Design of powder preheating for cold spray technology
Kalina, Jan ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
Cold spray is a technology that ranks among the thermal coatings. Its main idea is to prevent both the sprayed and the underlying material from reaching the melting temperature in order to reduce the level of surface oxidation. Cold spray is a relatively young technology that is still being researched. The effect of preheating the sprayed material on the material characteristics of the cold spray is one of the research questions. As part of this work, a device for preheating the powder to temperatures of up to 650 °C is designed in such a way as to minimize interference with the current construction of the Cold Spray workstation at the ÚMVI FSI BUT in Brno. The design is based on significant simplifications of the thermal model of the preheating device and heat losses. In the theoretical part, the reader was introduced to the history of Cold Spray, the effects of various technological parameters of Cold Spray on the resulting spray. Furthermore, the requirements for the preheater device were discussed, several variants of the device design were proposed, and the equations used for the device design were written. In the practical part, the required data for the design of the equipment is obtained for the required materials of the sprayed material, different temperatures, and other input parameters of the Cold Spray injection with the help of equations from the theoretical part. Based on them, the final design of the preheater device is compiled.
Influence of Process Parameters and Heat Treatment on the Structure and Properties of Cold Spray Method
Lindner, Patrik ; Řehořek, Lukáš (referee) ; Hutařová, Simona (advisor)
The bachelor thesis is a research of the state of knowledge focused on Cold spray technology and process parameters affecting the properties of coating, such as pressure, temperature, nozzle speed, sequence of individual layers, size of powder and others. This technology uses the kinetic energy of the impact of particles on the substrate. The main advantage of this method is possibility of forming a coating of large thicknesses (in millimeters) without oxides, with relatively low porosity and favourable mechanical properties. Aim of this work is to get acquainted with the Cold spray technology and the influence of process parameters on the quality of the spray. The influence of process parameters on properties is also demonstrated by own experimental results.
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.

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