Search

Erosion process of the Abrasive Water Jet (AWJ) machining on a rock material depends on various parameters. A brittle rock material is removed predominantly by the deformation wear. Abrasive grains can enhance the machining since their hardness and therefore material removal is better than work of pure water. However, to this day, determination of an optimal dosage of the abrasive matter entering into the mixing chamber was rather neglected. Based on the laws of conservations of momentum and energy combined with some empirical facts, it is possible to derive an equation for erosion of the material and subsequently another relation that provides estimation of the optimal mass flow rate of an abrasive matter. The main equation for erosion consists of six experimental coefficients, for an intensive AWJ only four, describing the effectivity of the water jet kw and abrasive jet ka impacting the material. It seems that the energy that is used for erosion is very small and the ideal dosage of the abrasive material is approximately Ṁa ≈ ṁw·(1 − 2kw/ka), where Ṁa and ṁw are the abrasive and water mass flow rates. Such an equation could be used for setting of AWJ machines. The economical optimum (eo) for cutting is proposed via the relation eo = E/Emax − R/Rmax, with the erosion E and its maximum value and the resistivity R and its maximum value.

The Ice abrasive water jet technology uses cryogenically cooled ice particles instead of the mineral abrasive used in the Abrasive water jet technology. The aim is to avoid contamination of workpieces with mineral abrasives and to reduce the environmental impact of this technology. The ice particles are sucked into a high-speed water jet with speeds of up to 600 m∙s$^{−1}$ using the Venturi effect. Direct observation of the process is very difficult due to the extreme operating conditions. We have clearly shown that at least some of the ice particles, which have cryogenic temperatures when entering the high-speed water jet, neither completely melt nor are completely crushed in contact with the jet. Further on, the erosion capability of ice particles was evaluated by blasting the aluminium and glass surfaces at two impinging angles and compared to garnet mineral abrasive, showing that ice particles have the potential to generate similar damage in the workpiece material as garnet. These findings pave the way for exploring the potential of abrasive waterjet technology in a wide range of new applications, such as food processing, medical implant and turbine blade manufacturing, and post-processing of parts manufactured with additive manufacturing technologies.

This paper deals with visualization and velocity analysis of a self-excited water jet generated by a designed prototype of hydrodynamic nozzle. The high-speed camera in combination with four high-energy pulsed LED lights and the particle image velocimetry method were tested. The influence of water pressure on the jet shape, velocity field and frequency of the self-excited jet was studied. The designed diagnostic water line consisting of pressure sensors and a turbine flowmeter was used for flow monitoring during experimental flow visualization. It was observed that the used optical equipment is suitable for velocity-frequency investigation up to 40 MPa with the maximal jet velocity 247 m/sec, 4.5 kHz oscillation frequency. The overall speed dependence of velocity on the distance downstream from the nozzle outlet (0–100 mm) decreases by 13–15% for tested pressure levels. Oscillation of self-excited jet in the 10–40 MPa pressure range is changing in range 2.5–4.5 kHz.

The paper deals with tangential abrasive water jet (AWJ) turning of Incoloy alloy 925. The aim of the experiment was to analyze the impact of the AWJ traverse speed (1.5–9 mm/min) on the surface quality in terms of micro-structure formed on the created surface. The water pressure was set to 400 MPa and the spindle revolution to 34 rpm. Australian garnet (MESH 80) was used as an abrasive component. The surfaces were visualized and qualitatively described using a laser confocal microscope. Basic roughness parameters of the surfaces (Ra, Rq, Rz) were measured using an optical profilometer. The presented experimental results demonstrate that the technology of abrasive water jet turning is an appropriate tool for rough machining of difficult-to-machine materials.

The pressure of the waterjet influences the overall performance of the abrasive waterjet cutting system through operational and phenomenological effects. In this study, the effect of water pressure in surface quality of Mg-based nanocomposite was investigated. The as-machined surfaces were examined by field emission scanning electron microscope to determine the surface morphology. The surface topography of selected nanocomposite was examined and compared. The results show that the surface quality is better at higher pressure. However, at lower water pressure, there is too much interaction among the low-energy abrasive particles and this may cause insufficient material removal. Abrasive waterjet cutting seems to be promising tool for machining metal matrix composites in terms of no thermal damages, no micro-structural changes and negligible sub-surface damages on the machined surface.

Abrasive water jet turning is one of the recently developed manufacturing technologies. It has gained its importance due to its capability to machine difficult-to-cut material with advantages such as absence of thermal effects, high machining flexibility and little cutting force. In this study, the influence of water jet turning parameters such as abrasive type and abrasive mass flow rate has been analysed on the variation of diameter with the target diameter of metal matrix composite. Composite material A359/Al2O3/B4C fabricated by electromagnetic stir casting process was used in the experiment. To select the level of parameter, one-variable-at-a-time analysis was used. The results revealed that the abrasive type had a greater influence on the deviation of diameter from the target diameter as compared to mass flow rate.

This paper deals with performance analysis of disintegration of polymethylmethacrylate using pulsating liquids jet with different density with frequency 20 kHz using condition monitoring. The influence of the liquid on the cutting depth was studied by using contactless measurement device MicroProf, FRT. The cutting depths were compared to studies that used a continuous water jet to assess the volume flow reduction. On-line condition measurement was used for controlling the disintegration process without compromising the structural integrity of neighbouring materials. With a flow rate of 0.54 l/min, a maximum disintegration depth of 1.3 mm and material removal of 0.4 mm3 was obtained using physiological saline and 1.1 mm and 0.2 mm3 for water. Continuous jets required approximately 1.0 l/min to reach similar cutting depths. Hence, a pulsating liquid jet enhances the cutting capacity with reduced flow rate. Signal strength for individual pressures 7–10 MPa is not significant, but signal increases during significant bone cement removal. The results open new avenues for research a minimally invasive and non-thermal technique for on-line controlled processes for medical purposes.

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. Four concrete mixtures were prepared for tests of interaction of water jet with concrete. The samples were exposed to 200 °C and 600 °C and for comparison one third of samples were left unaffected. It was found, that both lower traversing velocity (cutting speed) and higher water pressure led to removal of higher amount of concrete. Higher temperature loading caused decrease of concrete strength and thus easier removal of surface layers by water jet. Concrete mixtures with basalt aggregate demonstrate higher resistance against water jet penetration regardless thermal loading compared to mixture with standard granodiorite aggregate. Presence of polypropylene fibres has substantial influence on concrete strength properties, however only marginal impact on resistance against water jet penetration.

Rusnak J., Zeleňak M., Valicek J., Kadnar M., Hloch S., Hlavacek P., Kusnerova M., Cep R., Kadnar J. , 2011. Measurement of titanium surface roughness created by non-conventional cutting technology . Res. Agr. Eng., 57 (Special Issue): S57–S60. The paper evaluates the surface roughness quality of the titanium samples created by abrasive waterjet (AWJ) and by CO 2 laser beam cuttings. The introduction describes the principle of the mechanical (contact) method as well as the roughness parameters used for the experiment results evaluation. The following parts summarise the experimental con ditions and the measurement methodology. The emphasis of this work is laid on the comparison of machined surfaces final quality for the selected traverse speeds.

Abrasive water suspension (AWS) is a progressive cutting technology used in many industrial applications. Potential of this technology is very high due to good mobility and flexibility of the cutting process. It is mainly applied in the fields of defusing explosives, repairing and dismantling of nuclear power plants, offshore applications and special industrial structures. Although this technology works very well, further improvement of basic components and optimization of the cutting process is vital. In this experimental work, the applicability of LIF (Laser Inducted Fluorescence) technique combined with PTV (Particle Tracking Velocity) was tested for the identification of velocities of abrasive particles at the output of a cutting nozzle. The combination of various pressure levels with different abrasive mass concentration was tested. The obtained results of abrasive particle velocities are presented in the paper., Procedia Engineering, 149, International Conference on Manufacturing Engineering and Materials, ICMEM 2016

The paper deals with the verification of suitability of water jet and abrasive water jet application for the disintegration of rotating samples of wood plastic composites (WPCs) with diameter d = 36 mm. The influence of selected technological factors (traverse speed of cutting head v [mm/min] and size of abrasive particles [MESH]) on the topography of resulting surfaces has in particular been studied. Surface topography and quality have been assessed using the methods of optical and confocal microscopy and optical profilometry. The presented procedures and results of experiments demonstrate the technology of abrasive water jet as an appropriate tool for the rough machining of WPCs and similar composite materials. In addition, the application of this technology can effectively solve the problem of the melting of the polymer matrix and its subsequent sticking to the functional parts of a cutting tool resulting from conventional turning.

Članak obuhvaća studiju uporabe ultrazvučnog pulzirajućeg mlaza vode odabranih svojstava za razgradnju veze ostvarene pomoću koštanog cementa između cementiranog bedrenog drška i trabekularnog koštanog tkiva, kao potencijalne tehnike za revizijsku artroplastiku. Šest tipova komercijalnog koštanog cementa baziranog na polimetil metakrilatu rabljeni su za ovo istraživanje. Cementi su miješani uz pomoć DePuy - SmartMix® CTS / vakumske zdjele za miješanje. Mehanička svojstva ojačanog koštanog cementa određena su nanoindentacijom. Uzorci koštanog cementa su razgrađeni primjenom tehnologije pulzirajućeg mlaza vode. Tlak vode se mijenjao između 8 i 20 MPa. Kružna mlaznica s promjerom otvora od 0,7 mm je rabljena za rezanje mlazom vode. Odstojanje od ciljanog materijala bilo je 2 mm, a poprečna brzina iznosila je 1 mm/s. Volumen odstranjenog materijala i dubina kreiranih tragova mjereni su pomoću MicroProf FRT optičkog profilometra. Rezultati pozitivno podupiru pretpostavku da pulzirajući mlaz vode ima potencijal biti odgovarajuća tehnika za brzu i sigurnu razgradnju koštanog cementa pri revizijskoj artroplastici., The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of the interface created by bone cement between cemented femoral stem and trabecular bone tissue as a potential technique for revision arthroplasty. Six types of commercial bone cements based on Polymethyl Methacrylate were used for investigation. The cements were mixed using the DePuy - SmartMix® CTS / vacuum mixing bowl. Mechanical properties of hardened bone cements were determined by nanoindentation. The bone cement samples were disintegrated using the pulsating water jet technology. The water pressure varied between 8÷20 MPa. A circular nozzle with an orifice diameter of 0,7 mm was used for water jetting. The stand-off distance from the target material was 2 mm and the traverse speed 1 mm/s. The volume of material removal and depth of created traces were measured by MicroProf FRT optical profilometer. The results positively support an assumption that pulsating water jet has a potential to be a suitable technique for the quick and safe disintegration of bone cement during revision arthroplasty.

An optimization of the design of the abrasive cutting head using the numerical simulation requires gathering as much information about processes occurring in the cutting head as possible. Detailed knowledge of velocities of abrasive particles in the process of abrasive water jet generation is vital for the verification of the numerical model. A method of measurement of abrasive particles at the exit of focusing tube using the FPIV technique was proposed and preliminary tests are described in the paper. Results of analysis of measured velocity fields are presented in the paper.

Članak se bavi proučavanjem uporabe kontinuiranog vodenog mlaza i nadzvučnog pulsirajućeg mlaza vode za dezintegraciju koštanog cementa. Koštani cement Pallacos R+G (ručno miješan) dezintegriran je ex-vivo. Mehanička svojstva koštanog cementa određena su pomoću nano-utiskivanja. Faktori u procjeni bili su tlakovi (40, 80, 120) MPa i poprečna brzina kontinuiranog mlaza vode, tlak (8, 10, 12, 14, 16, 20) MPa i tip prigušnice (ravna, kružna) za nadzvučni pulsirajući mlaz vode. Dubina prodiranja h (mm) mjerena je bezkontaktnim optičkim profilometerom MicroProf FRT. Rezultati predstavljaju prvi korak ka izvedivosti uporabe učinkovite tehnike vodenog mlaza tijekom reimplantacije cementiranih endoproteza, za uklanjanje koštanog cementa iz bedrenog kanala bez topline i mehaničkog oštećenja okolnog tkiva., The paper deals with the study of using continuous water jet and ultrasonic pulsating water jet for bone cement disintegration. Bone-cement Pallacos R+G (manually mixed) was disintegrated ex-vivo. Mechanical properties of the bone cement were determined by nano-indentation. Factors employed in evaluation were pressure (40, 80, 120) MPa and traverse speed for continuous water jet, pressure (8, 10, 12, 14, 16, 20) MPa and orifice type (flat, circular) for ultrasonic pulsating water jet. Depth penetration h (mm) was measured by non-contact optical profilometer MicroProf FRT. Results represent the first step towards feasibility of using effective water jet technique during reimplantation of cemented endoprosthesis, for bone cement removal from femoral canal without heat and mechanical damage of surrounding tissue.

Production of nanomaterials by formation of extreme plastic deformation ECAP (Equal-Channel Angular Pressing) is one way to prepare of nano-structures of engineering materials by multiple extrusion of materials into a neck area of sample tube with a rapid change in direction of loading and loading. Grain refinement and a structural grain diameter reduction at nano size can be achieved in this way while acting under extremely high pressures SIGecap [MPa] where there is an increase in the tensile strength SIGm [MPa], yield strength SIGkl [MPa] and the elastic modulus Emat [MPa] by reducing the elongation Ataņ [%], because of the implicit function (SIGm, Emat, SIGkl, Ataņ ...)=f(dzrnoi, Kplmati). There is a confrontation of our method of calculating with previously used calculations for granularity dzrno [μm according to the Hall-Petch relation. The confrontation of theoretical results show a close match and simultaneously prove that it is a physical-mechanical reciprocity and superposition resolution in relation to a so called neutral zone of deformation. Custom analytical solutions can be applied to solve a problem of determining stress SIGecap [MPa], respectively of extrusion force Fecap [N] to achieve a desired grain size. However this role has not been yet solved, because of previously used equations are being derived only on the basis of a geometry of system which do not provide adequate results. The extrusion of sample is therefore being performed in multiple cycles, is getting more expensive, is being extended, and an immediate state of material shall be governed only by a subjective estimation and technologist experience.

The paper deals with a possibility of abrasive waterjet application for disposal of discarded munitions. Based on the analysis of current state it has been found out that the surplus munitions and the discarded munitions are destroyed mostly by using conventional techniques such as dumping at sea, outdoors burning, outdoors detonation, mining detonation and also open burning with combustion neutralization. The main aim of this paper is to present a new way of munitions disposal with a view of increasing both the operator safety and environmental protection. In terms of material, discarded munitions are composed of several components and valuable materials that need to be evaluated as efficiently as possible. Special attention is given to the abrasive water jet application in technological line for disposal of discarded munitions., Rad se bavi mogućnošću primjene abrazivnog vodenog mlaza za zbrinjavanje odbačenog streljiva. Na temelju analize trenutačnog stanja utvrđeno je, da je višak streljiva i odbačeno streljivo uništeno većinom uporabom tradicionalnih tehnika kao što su istovarom u more, spaljivanjem na otvorenom, eksplozijom na otvorenom, rudarskom eksplozijom i izgaranjem na otvorenom s neutralizacijom izgaranja. Osnovni cilj ovog rada je prikazati novi način zbrinjavanja streljiva u cilju povećanja sigurnosti kako operatora tako i zaštite okoliša. S motrišta materijala, odbačeno streljivo se sastoji od nekoliko komponenti i vrijednih materijala koje je potrebno procijeniti što efikasnije. Dana je posebna pozornost na primjenu abrazivnog vodenog mlaza kod tehnoloških linija za zbrinjavanje odbačenog streljiva.

Advanced technological aspects of cement based composites have been recently focused on developing new materials, which are high performance and exhibit high compressive strength. Using of carbon nanotubes improve microstructure and properties of cement matrix and make them promising fillers into many engineering materials. In this paper, experiments oriented at the study of dispersion of CNTs in water with respect to their use in cement compositions are described and a novel method of CNTs dispersion in water using pulsating water jets is proposed.

Valicek J., Kadnar M., Hlavacek P., Rusnak J., Hloch S., Zeleňak M., Řepka M., Kusnerova M., Kadnar J., 2011. Shadow method for the evaluation of surface created by hydroabrasive dividing of materials . Res. Agr. Eng., 57 (Special Issue): S69–S73. The contribution deals with the analysis of the optical data obtained from the surfaces generated by hydroabrasive dividing of materials. The samples of different materials were prepared at the Academy of Sciences of the Czech Republic. The comparison of further results performed between the commercial contact profilometer HOMMEL TESTER T8000 and the contactless shadow method developed included its calibration. On the basis of the optical data analysis, the results evaluated especially the height irregularities of the surface topography caused by hydroabrasive cutting planes. The evaluation of the surface topography generated by abrasive waterjet was realised via spectral analysis. The amplitudefrequency analysis of the signals generated on surface topography was mainly realised. Keyword : disintegration of materials; optical method; roughness; measurements