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Department of material desintegration

Personnel
  • Ing. Josef Foldyna, CSc.
    head of the department
  • Ing. Libor Sitek, Ph.D.
    deputy head of the department
  • Ing. Pavel Jekl
  • Daria Novakova
  • Luděk Pivoda
  • Prof. Ing. Jaroslav Vasek, Dr.Sc.
Main research topics

Research activities of the department are aimed in particular at the high-speed water jet disintegration of rock and geomaterials. In addition, problems related to the rock cutting by mechanical tools, the determination of workability and abrasivity of rocks are solved marginally.

  • Intensification of high-speed water jet effects

    Research activities are directed to study of dynamic behavior of the pulsating water flow, definition of natural relations of processes of excitation and propagation of the high-frequency pressure pulsations in the liquid and their utilization for the generation of pulsating high-speed liquid jets. The objective of the research is to understand fundamental processes of generation and transmission of pressure pulsations in the high-pressure system, forming of the pulsating jet and its interaction with the material.

  • Abrasive materials for abrasive water jet

    The topic covers the research in the area of new abrasive materials (both natural and artificially produced). The research is aimed at the definition of crucial properties of abrasive materials from the point of view of both maximizing the cutting performance and minimizing the wear of cutting head as well as their negative impacts on working and living environment. The objective of the research is development of the new generation of abrasive materials.

  • New areas of high-speed water jet utilization

    The research is oriented primarily at the machining using the abrasive water jet to enable machining (turning, milling, polishing, drilling, etc.) of difficult-to-machine and non-machinable materials, such as composites, ceramics, high-strength alloys, glass, rocks, etc., and at the utilization of high-speed water jets for ultra-fine grinding and disintegration of materials (primarily geomaterials) in the area of production of submicron particles.

Important scientific achievements

  • Acoustic generator of pressure pulsations

    A new method of acoustic generation of pulsations of liquid jet was developed and an apparatus utilizing the method for generation of pulsating liquid jet was designed, manufactured and tested. Pressure pulsations generated by acoustic actuator in acoustic chamber filled with pressure liquid are amplified and transferred by liquid waveguide to the nozzle. Liquid compressibility and tuning of the acoustic system are used for transfer of pulsating energy from the generator to the nozzle. Tests have proved considerably higher performance of pulsating water jet in material cutting compared to continuous one under the same operating conditions. This is due to effects of the impact pressure generated by an impact of pulsating jet on the target material and fatigue loading of the material.

  • Numerical model of acoustic generator

    CFD model of the high-pressure system with the integrated acoustic generator of pulsations was created. The model consists of the cylindrical acoustic chamber, the liquid waveguide fitted with the pressure liquid feed and the nozzle. The fluid flow in the model is solved as 3-D turbulent compressible unsteady isothermal single phase flow of water. The relatively good conformity of the simulation and experimental results was verified by the comparison of results of the simulation with the laboratory measurement of the dynamic pressure in the high-pressure system.

  • Visualization of pulsating jet

    A special method of visualization of pulsating water jets based on the application of stroboscopic effect was elaborated. The frequency of stroboscope flashing is controlled by the frequency of the pressure pulsations in the high-pressure system generating the pulsating jet. The visualization is used to study influence of operating parameters and the geometric configuration of the acoustic generator of pressure pulsations on the forming and the morphology of the pulsating water jets.

  • Abrasives for high-speed water jet technologies

    Abrasive materials were evaluated both from mineralogical and petrological points of view and also from the point of view of their behavior during the process of abrasive water jet generation and its action on material to be cut. Methodologies for assessment of initial properties of abrasive concentrates, their cutting efficiency in reference materials and wearing effects on focusing tube were developed together with methodology for description and morphological analysis of grains and cutting kerfs in macro- and micro-scales by image analysis. Determination of biological noxiousness of respirable dust fraction resulting from disintegration of natural and synthetic abrasives and minerals of the quartz group during application of abrasive water jet represents another original result of the research. The work contributed to formulation of both enduring problems and new themes for further research in the above mentioned area.

Technical equipment
  • High pressure pump based on unit Hammelmann equipped with intensifier Flow (maximum operating pressure 380 MPa, max. flow rate up to 3.5 liters per minute) including accessories (filtration unit, high-pressure tubes, etc.)
  • High pressure pump PTV 37-60 (one intensifier, maximum operating pressure 415 MPa, maximum flow rate up to 3.68 liters per minute) including accessories
  • High-pressure plunger pump KUNZ Hranice (maximum operating pressure 120 MPa, max. flow rate up to 45 liters per minute)
  • X-Y cutting system Nessap 1000-V specially designed for water jet and abrasive water jet cutting
  • Three-component dynamometer Kistler with charge amplifier
  • Four highly sensitive piezoelectric pressure sensors Kistler with charge amplifiers
  • Patented sensor for measurement of the jet stagnation force (patent No. PV 7884-1988)
  • Acoustic generator of pulsating jet
  • Stroboscopic device for visualization of pulsating jet
  • Measuring station based on notebook equipped with multifunction DAQ device National Instruments (16-bit) and LabVIEW Full Development System software
  • Laboratory pressure plough for measurement of cutting forces and determination of rock workability
  • Device for measurement of rock abrasiveness according to standard ON 44 1121
  • Device for measurement of rock abrasiveness according to Cerchar methodology
Solved projects
  • Institutional Research Plan No. AV0Z30860518 Physical and environmental processes in lithosphere induced by anthropogenic activity – sectional task Water jet (Academy of Sciences CR).
  • Targeted research project No. 1QS300860501 Novel technique for cleaning and removal of surface layers and repair of concrete structures (Academy of Sciences CR, 2005-2008).
  • Grant project A 3086201 Mechanical cutting of rocks and processes of coal and rock disintegration – theoretical aspects, applications, prospect (Grant agency ASCR, 2002-2006).
  • Project of bilateral cooperation between CNR Italy and Academy of Sciences of the Czech Republic Cutting and disintegration of hard rocks with water jet assistance. Special instruments, approaches and evaluation of cutting and disintegration performance (2004-2006).
  • Project of bilateral cooperation between Academy of Sciences of the Czech Republic and Polish Academy of Sciences Application of advanced research methods to description of rocks and their discontinuities – sectional task Roughness measurement (2006-2008).
Selected publications
  • J. Foldyna, P. Martinec, L. Sitek: Testing of Industrial Types of Abrasives for Abrasive Water Jet Cutting. Proceedings of the 6th Pacific Rim International Conference on Water Jet Technology, Sydney 2000, Dunn, Meyer, Hood (eds.), CMTE Austra-lia, 2000, pp. 143 – 147.
  • J. Foldyna, P. Martinec, L. Sitek: Testing of Mineral Types of Abrasives for Abrasive Water Jet Cutting. Proceedings of the 2001 WJTA American Waterjet Conference, Hashish (ed.), WJTA, 2001, pp. 291 – 303.
  • J. Foldyna, P. Martinec, L. Sitek: Water jets in dimension stone cutting and surface treatment. Dimension Stone 2004. New Perspectives for a Traditional Building Material (Proceedings of the International Conference on Dimension Stone 2004, 14-17 June 2004, Prague, Czech Republic). Prikryl (ed.), A. A. Balkema Publishers, Taylor & Francis Group, London, 2004, pp. 303-308, ISBN 90 5809 675 0.
  • J. Foldyna, L. Sitek: Modulated vs. Continuous Jets: Performance Comparison. Proceedings of the 2001 WJTA American Waterjet Conference, Hashish (ed.), WJTA, 2001, pp. 523 – 535.
  • J. Foldyna, L. Sitek, V. Haban: Acoustic wave propagation in high-pressure system. Ultrasonics, Vol. 44, Supplement 1, 22 December 2006, pp. e1457-e1460, ISSN 0041-624X.
  • J. Foldyna, L. Sitek, P. Jekl, P. Martinec, J. Scucka: Pulsating water jets. Documenta Geonica 2005, Institute of Geonics ASCR Ostrava, 2005, pp. 18-29.
  • J. Foldyna, L. Sitek, P. Jekl, B. Svehla: Measurement of dynamic pressure and force effects of modulated water jet. Proceed-ings of the 7th Pacific Rim International Conference on Water Jetting Technology, Jeju 2003, Chung-In Lee, Seokwon Jeon, Jae-Joon Song (eds.), Korean Society of Water Jet Technology, 2003, pp. 125-132, ISBN 89-95026-6-2 93550.
  • J. Foldyna, L. Sitek, P. Martinec, J. Scucka, P. Jekl, M. Młynarczuk: Rock cutting by pulsing water jets. Eurock 2005 – Impact of Human Activity on the Geological Environment. Konecny (ed.), A. A. Balkema Publishers, Taylor & Francis Group, London, 2005, pp. 129 – 134, ISBN 04 1538 042 1.
  • J. Foldyna, L. Sitek, B. Svehla, S. Svehla: Utilization of ultrasound to enhance high-speed water jet effects. Ultrasonics So-nochemistry, Vol 11/3-4, 2004, Elsevier B. V., pp 131-137.
  • P. Martinec, J. Foldyna, L. Sitek, L. Bilkova, K. Barcova: Olivine as industrial abrasive for high-speed water jet technology. Proceedings of the 16th International Conference on Water Jetting, Lake (ed.), BHR Group 2002, pp. 287 - 297. ISBN 1 85598 042 8.
  • P. Martinec, J. Foldyna, L. Sitek, J. Scucka, J. Vasek: Abrasives for AWJ cutting. INCO -COPERNICUS No. IC 15-CT98-0821. Institute of Geonics, Ostrava, 2002, ISBN 80-86407-02-0.
  • L. Sitek, J. Foldyna, K. Soucek: Shaping of rock specimens for testing of uniaxial tensile strength by high speed abrasive water jet: First experience. Eurock 2005 – Impact of Human Activity on the Geological Environment. Konecny (ed.), A. A. Balkema Publishers, Taylor & Francis Group, London, 2005, pp. 545 – 549, ISBN 04 1538 042 1.
  • L. Sitek, J. Foldyna, J. Scucka, M. Młynarczuk, J. Sobczyk: Quality of bottom surface of kerfs produced by modulated jets. Proceedings of the 16th International Conference on Water Jetting, Lake (ed.), BHR Group 2002, pp. 359 - 368. ISBN 1 85598 042 8.
  • L. Sitek, J. Foldyna, J. Scucka, B. Svehla, L. Bodnarova, R. Hela: Concrete and rock cutting using modulated waterjets. Proceedings of the 7th Pacific Rim International Conference on Water Jetting Technology, Jeju 2003, Chung-In Lee, Seokwon Jeon, Jae-Joon Song (eds.), Korean Society of Water Jet Technology, 2003, pp. 235 – 244, ISBN 89-95026-6-2 93550.
  • L. Sitek, K. Soucek, J. Foldyna, L. Stas: Preparation of rock and geo-composite specimens for tensile tests by abrasive water jet. Proceedings of the 1st Euro-Mediterranean Symposium on Advances in Geomaterials and Structures - AGS´06, Darve, Doghri, El Fatmi, Hassis, Zenzri (eds.), LGC-ENIT, Tunisia, 2006, pp. 103 - 109, ISBN 978-9973-61-317-2.
  • L. Turcaniova, J. Kadarova, P. Imrich, T. Liptaj, J. Vidlar, J. Vasek, J. Foldyna, L. Sitek, P. Balaz: Reactivity of mechani-cal activated coals for special utilization. Journal of Materials Science 39 (16-17), Aug-Sep 2004, pp. 5467-5470.