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Removal of polyurea spray coatings from the surface of cement concrete by water jet technology
Ščučka, Jiří ; Bódi, Z. ; Hlaváček, Petr ; Klich, Jiří ; Martinec, Petr ; Foldyna, Josef
The paper is focused on the removal of polyurea spray coatings from the surface of cement concrete by the water jet technology. A series of experiments was conducted to disintegrate a defined polyurea spray coat layer on the surface of cement concrete tiles using different configurations of the water jet system. The results of these experiments have confirmed that the continuous water jet was highly effective in removing the spray coat, causing no damage to the concrete substrate underneath. The partial experimental results have also indicated that this process can be used to produce an anti-skid finish on polyurea spray coatings applied onto horizontal structures.
Fulltext: content.csg -  DOC
Plný tet: UGN_0398599 - DOC
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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.
Fulltext: content.csg - DOC
Plný tet: UGN_0398577 - DOC
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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.
Fulltext: content.csg - DOC
Plný tet: UGN_0398575 - DOC
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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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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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