National Repository of Grey Literature 239 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Kunčická, Lenka ; Král, Petr ; Dvořák, Jiří ; Kocich, R.
The report presents results of the analyses of biocompatible WE 43 Mg-based alloy processed by friction stir processing (FSP) at two different rotational speeds of 400 RPM, and 1200 RPM. The structures were observed by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD). Observations were primarily focused on characterizations of grains and textures, supplementary testing of mechanical properties was performed via tensile tests. The results of low angle grain boundaries fractions and grain sizes showed that both the processing methods led to significant grain refinement and recrystallization, the average grain diameter within the 1200 RPM sample was less than 2 μm. Texture observations showed slight tendencies of the grains to align in the {0001}〈101̅0〉 and {0001}〈112̅0〉 preferential orientations, however, the maximum intensities were only about two times random. Supplementary tensile tests confirmed the positive effects of FSP on structures and properties of both the samples.
Dvořák, Jiří ; Sklenička, Václav ; Král, Petr ; Kvapilová, Marie ; Svobodová, M. ; Šifner, J. ; Koula, V.
Current acoustic emission (AE) applications are preferably oriented to continuous monitoring of machine component operation. AE is a perspective non-destructive method for early prediction and identification of material defects to avoid a disaster of running equipment. The paper analyzes the measured data and analysis of signals at the level of individual emission events during the creep test of a copper based on the results of previously performed microstructural and fractographic analyses of its creep damage evolution and fracture. The aim of the model study is to contribute to the successful application of AE for real operating components of power equipments and thus to increase their operational safety.
Dvořák, Jiří ; Král, Petr ; Kvapilová, Marie ; Hrbáček, Karel ; Sklenička, Václav
Two cast and heat-treated NbC and TaC – strengthened cobalt superalloys have been developed for a precision casting of spinner discs for glass wool industry. In this work constant load creep tests in tension were carried out in argon atmosphere at three testing temperature 900, 950 and 1000 °C and at the initial applied stresses ranged from 40 to 200 MPa. All the tests were continued until the final fracture. The results of creep testing were combined with microstructural and fractographic examinations by means of light and scanning electron microscopy. A mutual comparison of creep characteristics of the investigated superalloys under comparable creep loading conditions showed that NbC-strengthened superalloy exhibited longer creep life than TaC-strengthened one. Further, it was found that carbide precipitation is the primary strengthening mechanism in both cobalt-base superalloys under investigation and the amount, morphology\nand type of carbides have the decisive effect on the creep properties including creep damage and fracture processes. By contrast, NbC-superalloy exhibited a more brittle character of creep fracture mode than TaCstrengthened superalloy. This study was initiated to investigate in more details creep deformation processes and the effect of the creep microstructure and damage evolution on both investigated superalloys. The different behaviour and properties of studied superalloys were explained based on the received results of this study.
Nehomogenita mikrostruktury a creep ECAP hliníku
Sklenička, Václav ; Král, Petr ; Ilucová, Lucia ; Saxl, Ivan ; Dvořák, Jiří ; Svoboda, Milan
High purity (99.99%) pure aluminium processed by equal channel angular pressing (ECAP) was examined in terms of the ECAP microstructure inhomogeneity and its creep behaviour. The results indicate that an inhomogeneity of the ECAP microstructure in mesoscopic scale may influence the creep behaviour of the pressed material.
Absorption of gaseous pollutants on membrane contactors
Král, Petr ; Dohnal, Mirko (referee) ; Svěrák, Tomáš (advisor)
The diploma thesis is devoted to the separation of a pollutant (NH3) from a water solution using an experimental technology device - membrane contactor. The theoretical part is mostly focused on the recent progress in the field of membrane contactors. The theoretical part also contains theory of absorption, chemisorption and microreactions, which is needed to understand the subject properly. The experimental part focuses on the construction of the experimental device and what does experimental device consist of. The efficiency of the device in transfer of ammonia to an nitrate salt of nitric acid solution was tested. At the end, experimental data are further discussed.
Development of Creep Damage in Similar Weld Joints of P92 Steel Pipe
Král, Petr ; Sklenička, Václav ; Kuchařová, Květa ; Svobodová, M. ; Kvapilová, Marie ; Dvořák, Jiří
The microstructure and creep behaviour of the welded joints of P92 steel pipe were\ninvestigated in order to determine the influence of orbital heat welding technology on the creep\nresistance. Creep specimens were machined from the welded joints. Tensile creep tests of welded\njoints were performed at 873 K using different stresses. The microstructure of tested specimens was\ninvestigated by scanning electron microscope Tescan equipped with an electron-back scatter\ndiffraction. The creep results showed that the creep fracture strain of the welded joints decreases\nwith decreasing value of applied stress. Microstructure investigation showed that fracture behaviour\nof welded joints is influenced by an enhanced cavity formation at grain boundaries in the heataffected\nzone causing lower fracture ductility.
Creep damage tolerance factor lambda of selected creep-resistant steels
Sklenička, Václav ; Kuchařová, Květa ; Dvořák, Jiří ; Kvapilová, Marie ; Král, Petr
The creep damage tolerance factor lambda as an important outcome of the continuum damage mechanics approach has been used to asses the creep fracture mode and the susceptibility of material to localized cracking at strain concentrations. In this work, using sets of our earlier published creep data of three advanced ferritic creep-resistant steels (T23 low alloy steel, P91 and P92 chromium steels) are analysed in terms of the creep damage tolerance factor lambda. It was found that the value of the creep damage factor lambda is not constant and depends on the creep loading conditions. The data analysis is followed by fractographic investigations, which is used to identify the creep fracture mode(s) experimentally.
The Problems of PR Agencies
Prytoliuk, Anna ; Král, Petr (advisor) ; Zlatić, Marija (referee)
Public relations is a deliberate, planned and sustained effort to establish and strengthen mutual the understanding between an organization and its clients. Today, public relations is a full-value institute which is fundamental from both theoretical and practical perspectives. The aim of the current thesis is to investigate the existing issues and problems in the activities of PR agencies. Also, to outline the main problems which may exist in the practice of PR agencies and to investigate those problems in the practical activities of selected Eastern European and Czech companies, to draw conclusions on how the problems in the practice of Eastern European and Czech companies compare and differ and to provide recommendations for the analyzed companies to minimize the negative effects of those problems. Both parts of the topic were analyzed: theoretical part from literature gave the base for the practical interview with managers of selected companies, which provided a complex picture of the topic.

National Repository of Grey Literature : 239 records found   1 - 10nextend  jump to record:
See also: similar author names
32 KRÁL, Petr
11 Král, Pavel
2 Král, Pavel,
32 Král, Petr
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