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Effects of water jet on heat-affected concretes - laboratory tests
Klich, Jiří ; Sitek, Libor ; Zeleňák, Michal ; Hlaváček, Petr ; Foldyna, Josef ; Bodnárová, L. ; Válek, J.
The paper is dealing with the effects of flat high-speed water jet on concretes affected by high temperature. Research should help to correct use of water jet technology in repair works on concrete structures especially after wildfires in tunnels, underground garages, etc., which are exposed to enormous thermal stress.
Fulltext: content.csg -  PDF
Plný tet: UGN_0392712 - PDF
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On the preparation of precursors and carriers of nanoparticles by water jet technology
Sitek, Libor ; Foldyna, Josef ; Martinec, Petr ; Klich, Jiří ; Mašláň, M.
High-speed water jet expanded into many fields of human activity over three decades due to its unique properties. Besides already traditional technological processes (cutting, machining, cleaning, demolition, etc.) it begins to find its way also to the comminution of mineral particles. The paper analyzes the possibility of particle comminution using an abrasive mixing head used to generate high-speed abrasive water jet and an impact of the jet to the solid perpendicular target made 256 from tungsten carbide. Phyllosilicate (i.e. layered silicate) particles of both micron and submicron sizes were made by this method. The particles are disintegrated along the cleavage surfaces. The method avoids the formation of secondary structural defects which is in contrast to mechanical methods of particles comminution (such as planetary milling, ball milling, milling by pressure air etc.).
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Erosion of metals by pulsating water jet
Klich, Jiří ; Foldyna, Josef ; Hlaváček, Petr ; Zeleňák, M. ; Ščučka, Jiří
The aim of the paper was to determine erosion effects of pulsating water jet impinging the surface of metal sample. The influence of repeated impacts of water pulses and impact velocity (operating pressure) on the erosion of metal surface was investigated. The development of erosion pattern with respect to number of impacts was analysed and discussed. It was found that erosion caused by repeated impacts of water pulses occurs in three stages. The stage of erosion of the surface can be determined by the behaviour of surface characteristics (such as Ra and Rz with respect to number of impacts of pulsating water jet.
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Testing of Nozzles
Foldyna, Josef ; Sitek, Libor ; Ščučka, Jiří ; Klich, Jiří ; Hlaváček, Petr
Based on the request made by the company NET Ltd. Staré Město pod Sněžníkem, tests of quality of nozzles for generation of high-speed water jet were performed at the Department of material disintegration of the Institute of Geonics AS CR, v. v. i., in Ostrava. Three nozzles provided by NET were tested. The nozzles were marked as nozzle CKM – A, nozzle CKM – B, and nozzle ACMK. The nozzle quality was evaluated by the determination of their discharge coefficient at various operating pressures and by visual inspection of the quality of the nozzle and the water jet.
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Study of the surface topography created by pulsating water jet
Klich, Jiří
The paper has followed to study of the surface topography created by the pulsating water jet. It presents a way to evaluate the surface topography created by the unconventional method. Based on data analysis and subsequent interpretation is described the surface generated pulsating water jet. Knowledge of this description is very important for dimensioning the optimum technological factors pulsating water jet in relation to the workpiece material and the required quality of the finished surface.
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