National Repository of Grey Literature 10 records found  Search took 0.01 seconds. 
The analysis of Cu-Sn-Sb ternary alloy
Kučera, Jan ; Doubrava, Marek (referee) ; Jan, Vít (advisor)
This bacholor thesis deals with substituting silver-based material, currently used for experimental semi-liquid extrusion. The proposed material is from the Cu-Sb-Sn system. The theoretical part of the work deals with soldering and phase diagrams. The experimental part is devoted to the analysis of three proposed alloys from the Cu-Sb-Sn system, their structural and mechanical properties. Thermal analyzes of the alloys were performed using differential scanning calorimetry (DSC), the microstructure using a light microscope and a scanning electron microscope, and a hardness tester was also used to determine the hardness. The results are summarized in the discussion.
Structure and Properties of Coatings Produced by PVD Technology
Doubrava, Marek ; Horynová, Miroslava (referee) ; Čelko, Ladislav (advisor)
The submitted work is focused on study of 3rd generation DLC films produced by Platit a.s. company. Thin films are deposited utilizing filtered cathodic vacuum arc process (FCVA). The main goal of thesis was to find out the influence on film properties, caused by change of the substrate holders with different heat dissipation. The change of the substrate holders is motivated purely by economical effort to increase productivity of the deposition process. Teoretical part of the thesis is about the principles of PVD deposition process, characterization of the thin films, DLC thin films and materials used for cutting tools. Experimental part includes description of devices used for specimens analyses, including also the description of measuring process and used conditions. Acquiered results, not only the thin film thickness, adhesion or amount of sp^3 bonds, match with expected results.
Analysis of welded joints after fatigue tests
Kučera, Ondřej ; Doubrava, Marek (referee) ; Havlík, Petr (advisor)
This bachelor thesis deals with analysis of welded joints after fatigue tests . The first part of this thesis, literary research, discusses weldability of carbon steels and low-alloy steels and effect of chemical composition on weldability of materials. Further there are zones of welded joints, their microstructure and mechanisms applied described in this thesis. There are defects occurring in welded joints and their common causes and remedies described in the part of literary research dealing with defects. And the final part of the literary research deals with material fatigue, fatigue of welded joints and effect of defects, fusion zone and heat-affected zone on the fatigue of welded joints. In the experimetal part of bachelor thesis there is described experimental material, results obtain process and discussion of results.
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.
Deposition of MMC-type composite coatings on steel substrates using the Cold Spray method
Šesták, Stanislav ; Doubrava, Marek (referee) ; Řehořek, Lukáš (advisor)
The Cold Spray method is a modern coating method characterized by several interesting advantages and drawbacks. One of the most significant drawbacks is the difficult manufacturing of materials with limited ductility. This work is dedicated to this issue, and its main objective is the development of tribological coatings for high-temperature applications on steel substrates. Extensive research focused on the nature of the chosen deposition method and its specifics in the context of materials with limited ductility is provided and concluded by a set of methodical approaches of deposition, which are verified in the experimental part of this work. The experimental part focused on processing Ni-B4C and Ni-SiC composite coatings, in which the reinforcement particle volume fraction was chosen as 20 and 40 %. All coatings were deposited on 42CrMo4 steel substrates. The analysis of the coatings consisted of microstructure evaluation (using optical and electron microscopy) hardness testing and adhesion testing. The Ni-SiC coating consisting of 40 vol.% SiC particles showed the best properties; compared to other coatings it offered the highest microstructural quality and microhardness values. This coating was found suitable for the chosen application, and further suggestions on improving the quality of this coating were provided in this work’s conclusion.
Cold spray technology as a tool for repairing of worn parts
Hevessy, Zoltán ; Heczko, Martin (referee) ; Doubrava, Marek (advisor)
Cold spray (CS), also known as cold dynamic gas spraying, is a state-of-the-art process from the thermal spray family, characterized by a combination of low temperature and high velocity of the particles, which makes coatings of sufficient quality for applications in many industries where other processes cannot be used, including repairs of civil and military aircraft and helicopters. The bachelor thesis presents a detailed description of this process, the influence of its parameters on the quality of the coatings, examples of repairs and evaluation of the mechanical and corrosion properties of the repaired parts.
Analysis of welded joints after fatigue tests
Kučera, Ondřej ; Doubrava, Marek (referee) ; Havlík, Petr (advisor)
This bachelor thesis deals with analysis of welded joints after fatigue tests . The first part of this thesis, literary research, discusses weldability of carbon steels and low-alloy steels and effect of chemical composition on weldability of materials. Further there are zones of welded joints, their microstructure and mechanisms applied described in this thesis. There are defects occurring in welded joints and their common causes and remedies described in the part of literary research dealing with defects. And the final part of the literary research deals with material fatigue, fatigue of welded joints and effect of defects, fusion zone and heat-affected zone on the fatigue of welded joints. In the experimetal part of bachelor thesis there is described experimental material, results obtain process and discussion of results.
The analysis of Cu-Sn-Sb ternary alloy
Kučera, Jan ; Doubrava, Marek (referee) ; Jan, Vít (advisor)
This bacholor thesis deals with substituting silver-based material, currently used for experimental semi-liquid extrusion. The proposed material is from the Cu-Sb-Sn system. The theoretical part of the work deals with soldering and phase diagrams. The experimental part is devoted to the analysis of three proposed alloys from the Cu-Sb-Sn system, their structural and mechanical properties. Thermal analyzes of the alloys were performed using differential scanning calorimetry (DSC), the microstructure using a light microscope and a scanning electron microscope, and a hardness tester was also used to determine the hardness. The results are summarized in the discussion.
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.
Structure and Properties of Coatings Produced by PVD Technology
Doubrava, Marek ; Horynová, Miroslava (referee) ; Čelko, Ladislav (advisor)
The submitted work is focused on study of 3rd generation DLC films produced by Platit a.s. company. Thin films are deposited utilizing filtered cathodic vacuum arc process (FCVA). The main goal of thesis was to find out the influence on film properties, caused by change of the substrate holders with different heat dissipation. The change of the substrate holders is motivated purely by economical effort to increase productivity of the deposition process. Teoretical part of the thesis is about the principles of PVD deposition process, characterization of the thin films, DLC thin films and materials used for cutting tools. Experimental part includes description of devices used for specimens analyses, including also the description of measuring process and used conditions. Acquiered results, not only the thin film thickness, adhesion or amount of sp^3 bonds, match with expected results.

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2 Doubrava, Michal
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