National Repository of Grey Literature 77 records found  beginprevious48 - 57nextend  jump to record: Search took 0.04 seconds. 
Influence of the transition area on efficiency of the water jet cutting
Říha, Zdeněk ; Foldyna, Josef ; Hlaváček, Petr
The transition area between big and small pipe diameter in the tool for water jet cutting creates subject of researching. Three kinds of transition areas were tested such as conical change, radius change and step change. The efficiency of the water jet cutting was evaluated for above mentioned transition areas. This work brings new possibilities for design of the water jet cutting tool.
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Plný tet: UGN_0398579 - Download fulltextDOC
Preliminary analysis of volume material removal at bone cement disintegration by pulsating water jet
Lehocká, D. ; Hloch, S. ; Foldyna, Josef ; Monka, P. ; Monková, K. ; Brezíková, K.
The article deals with preliminary analysis of material removal during disintegration of bone cement. This article was created to show possibilities of pulsating water jet utilization in medicine. Experiments with pulsating water jet were done using two types of nozzles - flat and round. Traces in bone cement were measured by optical profilemeter MicroProf FRT. Results show that pulsating water jet will be possible focuses as a tool for medical purposes, but further detailed research is needed.
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Plný tet: UGN_0398578 - Download fulltextDOC
Effects of pulsating water jet on materials with variously modified surface
Klich, Jiří ; Klichová, Dagmar ; Hlaváček, Petr
The paper deals with determination of erosion effects of pulsating water jet impinging the surface of aluminium alloy samples treated by various techniques (rough and fine milling, planing and rolling). The influence of the initial surface topography on the final topography of the sample exposed to pulsating water jet was investigated. Erosion of surface layer was analysed and discussed with respect to the traversing velocity of the jet. It was found, that properties of the initial surface have a significant impact on the final topography. Degree of erosion of the surface was determined by the measurement of surface parameter Ra.
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Plný tet: UGN_0398577 - Download fulltextDOC
Measurement and evaluation of pulsating water jet peening intensity
Hlaváček, Petr ; Klich, Jiří ; Foldyna, Josef ; Sitek, Libor
Pulsating water jet peening is a promising method in surface treatment. It has the potential to induce compressive residual stresses that benefit the fatigue life of components similar to the other peening process. In this paper experimental results obtained by action of pulsating water jet on Almen strips are presented.
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Plný tet: UGN_0398576 - Download fulltextDOC
The measurement of the velocity of abrasive particles at the suction part of the cutting head
Foldyna, Josef ; Zeleňák, Michal ; Klich, Jiří ; Hlaváček, Petr ; Sitek, Libor
To be able to optimize the design of the abrasive cutting head using numerical simulation, it is necessary to gather as much information about processes occurring in the cutting head as possible. The development of the numerical model of processes occurring in the abrasive water jet cutting head during the process of creation and forming of abrasive water jet is currently in progress at the Institute of Geonics in Ostrava. The verification of the model requires, among others, to determine the behaviour of abrasive particles at the input of the cutting head. Therefore, the visualisation of abrasive particles at the input using various parameters of abrasive jet and its subsequent analysis was performed using shadowgraphy (backlighting) technique and the results are presented in the paper.
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Plný tet: UGN_0398575 - Download fulltextDOC
Pulsed liquid jet generated by pulse multiplication technique
Dvorský, R. ; Sitek, Libor ; Sochor, T.
First theoretical papers summarizing the high mechanical energy cumulation when high-speed drops impacting the solid surface as a result of the water hammer effect have been known since 1960’s. Heymann has demonstrated that pressure maximum in the impact of a spherical drop of a liquid is several times higher than the presupposed maximum for the classical water hammer effect. The latter maximum pressure itself exceeds the mere stagnation pressure of the continuous jet many times hereat. When developing devices for pulse jet generation a new generalization of the classical water hammer theory for high pressures has been implemented. Based on this the new patented principle of “pulse multiplication” has been formulated. The pulse multiplier is the source of high-pressure pulses with 100% depth of modulation of liquid jet discharge velocity that allows increasing the jet disintegration effect significantly without the abrasive material application.
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Plný tet: UGN_0398574 - Download fulltextDOC
Study of behavior of concrete and cement based composite materials exposed to high temperatures
Bodnárová, L. ; Horák, D. ; Válek, J. ; Hela, R. ; Sitek, Libor
The paper describes possibilities of observation of behaviour of concrete and cement based composite material exposed to high temperatures. Nowadays, for large-scale tests of behaviour of concrete exposed to high temperatures, testing devices of certified fire testing stations in the Czech Republic and surrounding states are used. These tests are quite expensive. For experimental verification of smaller test specimens, a testing device was built at the Technical University in Brno, where tests of thermal loading of concrete tests specimens of various sizes can be carried out (dimensions up to 800 x 800 x 800 mm or slabs up to 1100 mm of length). The testing device opens new ways of observation of behaviour of concrete and cement based composite materials exposed to high temperatures as well as preparation of specimens for observation of interaction of water jet and concrete degraded by action of high temperatures.
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Water Jet 2013 - Research, Development, Applications. Proceedings of the Conference on Water Jetting Technology
Sitek, Libor ; Klichová, Dagmar
Water Jet 2013 - Research, Development, Applications is the third international meeting of researchers, manufacturers, end-users, and all those interested in the technology of high-speed water jetting organized by the Department of material disintegration of the Institute of Geonics of the ASCR Ostrava. It provides a basis not only for exchange knowledge, ideas, information and experiences in areas of research, development and applications of water jets, as well as stimulating discussions, but also opportunity to make new acquaintances and friends. Number and diversity of papers submitted to the conference indicate permanent great interest in the water jetting technology and continuous expansion of water jets to new fields of human activities
The new finding of a K- bentonite ( tuffite ) seam 22b ( 080.2 OKD " tuffite Ivan " ) in Petřkovice Mbr Ostrava Formation ( Namur A) in the Czech part of the Upper Silesian Basin
Martinec, Petr ; Hoch, I. ; Ščučka, Jiří
New finding of a K-bentonite (tuffite) horizon comes from a mine borehole Staric II 938/13 (depth of 7,6 - 7,62 m). It belongs to the Petrkovice Mbr (Namurian A, Pendleian) in the Ostrava Fm. It occurs 2,3 m in overburden of coal seam 22b (080.2 numeration after Ostrava Mine District). The horizon is located 58 m above the coal tonstein of the coal seam 21d (077 OKD). This K-bentonite horizon is of local importance and will be used for correlation of coal seams in mine field Staric in the Czech part of the Upper Silesian coal basin.
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Plný tet: UGN_0398227 - Download fulltextDOC
Composition and properties of organic matter in freshwater clays of the lower Cenomanian ( Peruc Mbrs ) from the slope of Litice Chlum in Zamel , East Bohemia
Martinec, Petr ; Sýkorová, Ivana ; Havelcová, Martina ; Trejtnarová, Hana ; Šulc, Alexandr ; Kubina, Lukáš
The new finding of coal bearing kaolinite claystone in the Peruc Mbr occurring at the western hillside of Litice Chlum Hill in Zamel near Potstejn has contributed to expanding our knowledge of Czech Republic‘s Lower Cenomanian sediments. The petrographic and chemical investigation was focused on elucidating the composition of the fine-grained sediment and the origin of the organic matter present therein. However, the forms of organic matter preserved in the claystones bring evidence of the existence of an overlay of plant origin of which the residues may have been carried by water and wind to the vicinity of Lower Cenomanian riverbeds. The greater abundance of inertinite macerals coupled with the presence of semicoke representing the remains of incomplete combustion occurring during wildfires also documents the occurrence of polycyclic aromatic hydrocarbons and the distribution of n-alkanes exhibiting an unusual maximum.
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Plný tet: UGN_0398222 - Download fulltextDOC

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