Effects of continuous and pulsating water jet on CNT/concrete composite

This paper presents first results of the study of the resistance of carbon nanotube concrete composite (CNT/concrete composite) to the action of continuous and pulsating water jets. The experiments oriented at the determination of erosion effects of pulsating and continuous water jets impinging the surface of reference (concrete) and CNT/concrete composite samples were performed. Tested samples were characterized by X-ray powder diffraction and scanning electron microscope. Samples were exposed to pulsating and continuous water jets at various operating parameters. Erosion effects of pulsating and continuous jets were evaluated in terms of material removal rate. The possible influence of addition of CNTs to the concrete on its resistance to the action of continuous and pulsating water jets is discussed in the paper. The experiments proved that CNT/concrete composite exhibits higher resistance than reference concrete to the action of both pulsating and continuous water jet under the given testing conditions.Web of Science631058958

Influence of electric discharges on bearings of electric machina

Bearing currents are one of cause’s bearings faults. The character of a lubricator belongs to main factor influencing an inception of bearing currents. We have analyzed the electric character variety kind of lubricators; the influence of lubricators on a bearing current was analyzed too. Some results from the mentioned research are introduced within this paper

Erosion of metals by pulsating water jet

Cilj rada bio je utvrditi eroziju uzrokovanu pulsirajućim vodenim mlazom koji udara o površinu metalnog uzorka. Istražen je utjecaj ponovljenih djelovanja vodenih impulsa i utjecaja brzine (radnog tlaka) na eroziju metalne površine. Analiziran je i raspravljen razvoj erozijskog modela u odnosu na broj djelovanja. Utvrđeno je da se erozija uzrokovana opetovanim djelovanjem vodenih impulsa ​​javlja u tri faze. Faza erozije površine može se odrediti pomoću ponašanja karakteristika površine (kao što su Ra i Rz) s obzirom na broj djelovanja pulsirajućeg vodenog mlaza.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

Surface Integrity Evaluation of Brass CW614N after Impact of Acoustically Excited Pulsating Water Jet

AbstractPresented article is focused on surface integrity evaluation of brass CW614N form the sight of surface topography, structural changes in surface layers and strengthening character in subsurface layers after impact of acoustically excited pulsating water jet (PWJ). Surface topography was evaluated using optical profilometry. Structural changes in subsurface layer were observed based on mass material removal Δm [mg/s] and maximal depth of penetrance of PWJ hmax [mm]. Nano indentation measurement according to Berkovich were used to examination of strengthening character in subsurface layer. Disintegration of experimental samples was performed under constant technological conditions: hydraulic power of plunger pump Ph = 19kW; round nozzle diameter d = 1.6mm; feed speed rate v = 0.75mm/s; pressure of plunger pump p = 38MPa, stand-off distance of nozzle from target material z = 45mm; ultrasound frequency f = 20.29kHz and as variable factor was set power of ultrasound P on values 340, 360 and 380W. In terms of surface topography experimental investigation proved that PWJ under selected conditions is not suitable for precision machining. Evaluation of the surface characteristics indicates that the chemical composition has a significant effect on material weight loss Δm [mg/s] and a maximum depth of penetration of PWJ hmax [mm]. Evaluation of characteristics of subsurface layer was observed strengthened area with lower elasticity

On the preparation of precursors and carriers of nanoparticles by water jet technology

Uporaba vodenog mlaza velike brzine proširila se u mnoga područja ljudskog djelovanja zbog njegovih jedinstvenih svojstava. Uz već tradicionalne tehnološke postupke počinje se primjenjivati u usitnjavanju mineralnih čestica. U ovom se radu analizira mogućnost usitnjavanja čestica primjenom abrazivne glave za miješanje koja stvara abrazivni vodeni mlaz velike brzine koji udara u čvrstu okomitu metu od volfram karbida. Čestice filosilikata (tj. sloja silikata) dimenzija kako mikrona tako i submikrona dobivene su ovom metodom. Ovom se metodom izbjegava stvaranje sekundarnih strukturnih defekata suprotno mehaničkim metodama usitnjavanja čestica. Nekoliko tipova mika (muskovit, vermikulit i biotit) i sitnozrnati kaoliniti usitnjeni su primjenom tehnologije vodenog mlaza. Rad se također bavi mogućnostima daljnje promjene dimenzija zrna čestica silikata te korištenja tako pripremljenih čestica kao supstance ili nositelja nanočestica.High-velocity water jet expanded into many fields of human activity due to its unique properties. Besides already traditional technological processes 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-velocity abrasive water jet and an impact of the jet to the solid perpendicular target made from tungsten carbide. Phyllosilicate (i.e. layered silicate) particles of both micron and submicron sizes were made by this method. The method avoids the formation of secondary structural defects which is in contrast to mechanical methods of particles comminution. Several types of micas (muscovites, vermiculite and biotite) and fine-grained kaolinites were comminuted using high-velocity water jet technology. The paper also deals with the possibilities of further change of silicate particles grain size and of using such prepared particles as precursors or carriers of nanoparticles

Comparison of the actual costs during removal of concrete layer by high-speed water jets

This paper describes the process of possible evaluation of costs of using high speed water jet technology for concrete removal methods. High speed water jet technology is a progressive technology of removing damaged concrete used in civil engineering since the 80's of 20th century. It has been changing and developing since that time. But there is little information in literature devoted to the economic evaluation of this technology. Detailed economic analysis is still missing. This paper aims to compare comprehensively in economic terms the costs of removing concrete using the technology of both continuous oscillating and pulsating oscillating water jets. The research was realized in cooperation with research institutions and industrial companies and was supported by state budget of the Czech Republic and from the European Union. The scheme of cooperation of the University, research institutions, industrial companies and government follows the Triple helix model

Elektrický kontakt v ložisku

Import 30/07/2008Prezenční453 - Katedra elektrických strojů a přístrojůNeuveden

Příprava laboratorní úlohy "Ověřování magnetických vlastností materiálů pro stavbu elektrických strojů a přístrojů"

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (453) elektrických strojů a přístroj

Magnetické pole v okolí asynchronního stroje, jeho zjišťování a využití

V okolí každého provozovaného elektrického stroje je různě veliké magnetické pole. Jedná se o rozptylové pole generované tímto strojem. Toto pole je možno měřit a jeho analýzou získáme informace, které mohou signalizovat závadu či počínající poruchu stroje. Příklady takových měření a jejich srovnání s výsledky jiných diagnostických metod budou uvedeny v našem příspěvku