Number of found documents: 997
Published from to

DETEKCE PORUCH POMOCÍ AKUSTICKÉ EMISE (AE) V PODMÍNKÁCH VYSOKOTEPLOTNÍHO CREEPU
Dvořák, Jiří; Sklenička, Václav; Král, Petr; Kvapilová, Marie; Svobodová, M.; Šifner, J.; Koula, V.
2019 - Czech
Současné aplikace akustické emise (AE) jsou přednostně orientovány na průběžný monitoring provozu strojních komponent. AE je perspektivní nedestruktivní metodou pro včasnou predikci a identifikaci poruch materiálu dříve než dojde k havárii sledovaných zařízení. Příspěvek analyzuje naměřená data a rozbor signálů na úrovni jednotlivých emisních událostí v průběhu creepové zkoušky mědi na základě výsledků předchozí mikrostrukturní a fraktografické analýzy jejího creepového porušení a lomu. Cílem modelové studie je přispět k úspěšné aplikaci AE pro reálné provozní komponenty energetických zařízení a tím ke zvýšení jejich provozní bezpečnosti. Current acoustic emission (AE) applications are preferably oriented to continuous monitoring of machine component operation. AE is a perspective non-destructive method for early prediction and identification of material defects to avoid a disaster of running equipment. The paper analyzes the measured data and analysis of signals at the level of individual emission events during the creep test of a copper based on the results of previously performed microstructural and fractographic analyses of its creep damage evolution and fracture. The aim of the model study is to contribute to the successful application of AE for real operating components of power equipments and thus to increase their operational safety. Keywords: Acoustic emission; creep; coper Available at various institutes of the ASCR
DETEKCE PORUCH POMOCÍ AKUSTICKÉ EMISE (AE) V PODMÍNKÁCH VYSOKOTEPLOTNÍHO CREEPU

Současné aplikace akustické emise (AE) jsou přednostně orientovány na průběžný monitoring provozu strojních komponent. AE je perspektivní nedestruktivní metodou pro včasnou predikci a identifikaci ...

Dvořák, Jiří; Sklenička, Václav; Král, Petr; Kvapilová, Marie; Svobodová, M.; Šifner, J.; Koula, V.
Ústav fyziky materiálů, 2019

HYDROGEN SORPTION IN ORDERED Mg-In ALLOYS
Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
2019 - English
Hydrogen storage (HS) performance of three Mg- x In- y CB alloys (CB - amorphous carbon, x = 55, 64, 73 y =\n10 wt%) was studied. Indium concentration covered an area of ordered β structures. Alloys were prepared by\nball-milling in hydrogen atmosphere. Kinetic curves and PCT isotherms were measured in the temperature\ninterval from 200 °C to 325 °C. X-ray diffraction spectroscopy (XRD) was used for structure investigation. Alloy\nwith x = 73 wt% In ( β ’’ structure) showed reversible amorphization during temperature cycling between about\n100 °C and 350 °C. Hydrogen sorption experiments were done by the Sieverts method under the hydrogen\ngas pressure ranging from 0.1 MPa to 2.5 MPa. It was found that hydrogen sorption capacity varied between\n0.47 and 1.1 wt% H 2 . Hydride formation enthalpy ∆H calculated from desorption PCT experiments was\nsignificantly lower than ∆H , known for pure Mg. This invoked an idea that atomic order of Mg-based HS\nmaterials might decrease the high thermodynamic stability of hydride phase. Keywords: Hydrogen storage; Mg alloys; hydride stability; ordering Available at various institutes of the ASCR
HYDROGEN SORPTION IN ORDERED Mg-In ALLOYS

Hydrogen storage (HS) performance of three Mg- x In- y CB alloys (CB - amorphous carbon, x = 55, 64, 73 y =\n10 wt%) was studied. Indium concentration covered an area of ordered β structures. Alloys ...

Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
Ústav fyziky materiálů, 2019

PILOT ANALYSIS OF CHEVRON NOTCH LIGAMENT AREA FOR APPLICATION\nON QUASI-BRITTLE MATERIALS
Seitl, Stanislav; Růžička, P.; Miarka, P.; Sobek, J.
2018 - English
Specimens for the bending tests with the chevron notch are standardized for the\nevaluation of the fracture toughness of various materials. The main advantage of this test\nset-up is that no sharp pre-crack has to be introduced, because a sharp crack is formed\nduring loading at the beginning of the test. Furthermore, no crack length measurement is\nrequired, and a stable crack growth can be reached due to geometry of the notch. In this\ncontribution a difference of the ligament area of the specimens with the straight through\nnotch and the chevron notch was investigated Keywords: Fracture mechanics; chevron notch; ligament area; work of fracture; straight notch; blunt Available at various institutes of the ASCR
PILOT ANALYSIS OF CHEVRON NOTCH LIGAMENT AREA FOR APPLICATION\nON QUASI-BRITTLE MATERIALS

Specimens for the bending tests with the chevron notch are standardized for the\nevaluation of the fracture toughness of various materials. The main advantage of this test\nset-up is that no sharp ...

Seitl, Stanislav; Růžička, P.; Miarka, P.; Sobek, J.
Ústav fyziky materiálů, 2018

Study of mechanical properties of nanolayered Ti/Ni coatings
Zábranský, L.; Václavík, R.; Přibyl, R.; Ženíšek, J.; Souček, P.; Buršík, Jiří; Fořt, Tomáš; Buršíková, V.
2018 - English
The aim of the present work was to study the dependence of mechanical properties of Ti/Ni multilayer thin films on the thicknesses of constituent Ti and Ni layers. The multilayer thin films were synthesized by deposition of Ti and Ni layers alternately on single crystalline silicon substrates using direct current magnetron sputtering method. Thicknesses of Ti and Ni layers varied from 1.7 nm to 100 nm. The micro-structure of the multilayer films was studied using X-ray diffraction technique, scanning electron microscopy with focused ion beam technique and transmission electron microscopy. Mechanical properties obtained from nanoindentation experiments were discussed in relation to microstructural observations. Keywords: Ti/Ni; multilayers; magnetron sputtering; nanoindentation; TEM Available at various institutes of the ASCR
Study of mechanical properties of nanolayered Ti/Ni coatings

The aim of the present work was to study the dependence of mechanical properties of Ti/Ni multilayer thin films on the thicknesses of constituent Ti and Ni layers. The multilayer thin films were ...

Zábranský, L.; Václavík, R.; Přibyl, R.; Ženíšek, J.; Souček, P.; Buršík, Jiří; Fořt, Tomáš; Buršíková, V.
Ústav fyziky materiálů, 2018

INFLUENCE OF GRAPHITE UPON THE KINETICS OF HYDROGEN SORPTION IN Mg@Mg17Al12
Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
2018 - English
Influence of graphite addition to the ball-milling charge composed of Mg splinters and Mg17Al12 particles upon the hydrogen sorption was investigated at sorption temperature 623 K. Measurements were carried out by Sieverts method. Graphite facilitates the ball-milling: It prevents re-agglomeration of crushed particles into large secondary particles. It also suppresses sticking the milled material to the balls and walls of the milling jar. It was found that an increase of carbon concentration up to a certain limit c(L) lying between 14 and 23 wt. % C, carbon increases both the absorption and the desorption rates and hydrogen storage capacity. Above c(L), carbon causes a considerable decrease in HS capacity, which spoils the application potential of Mg@Mg17Al12/C. Crystallite size of the material under study, obtained by XRD, is in the order of tens of nm. Keywords: storage; Hydrogen storage; Mg alloys; graphite Available at various institutes of the ASCR
INFLUENCE OF GRAPHITE UPON THE KINETICS OF HYDROGEN SORPTION IN Mg@Mg17Al12

Influence of graphite addition to the ball-milling charge composed of Mg splinters and Mg17Al12 particles upon the hydrogen sorption was investigated at sorption temperature 623 K. Measurements were ...

Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
Ústav fyziky materiálů, 2018

HIGH - TEMPERATURE CREEP BEHAVIOUR OF CAST COBALT-BASE SUPERALLOYS
Dvořák, Jiří; Král, Petr; Kvapilová, Marie; Hrbáček, Karel; Sklenička, Václav
2018 - English
Two cast and heat-treated NbC and TaC – strengthened cobalt superalloys have been developed for a precision casting of spinner discs for glass wool industry. In this work constant load creep tests in tension were carried out in argon atmosphere at three testing temperature 900, 950 and 1000 °C and at the initial applied stresses ranged from 40 to 200 MPa. All the tests were continued until the final fracture. The results of creep testing were combined with microstructural and fractographic examinations by means of light and scanning electron microscopy. A mutual comparison of creep characteristics of the investigated superalloys under comparable creep loading conditions showed that NbC-strengthened superalloy exhibited longer creep life than TaC-strengthened one. Further, it was found that carbide precipitation is the primary strengthening mechanism in both cobalt-base superalloys under investigation and the amount, morphology\nand type of carbides have the decisive effect on the creep properties including creep damage and fracture processes. By contrast, NbC-superalloy exhibited a more brittle character of creep fracture mode than TaCstrengthened superalloy. This study was initiated to investigate in more details creep deformation processes and the effect of the creep microstructure and damage evolution on both investigated superalloys. The different behaviour and properties of studied superalloys were explained based on the received results of this study. Keywords: Co-based superalloys; creep tests; microstructure evolution; carbide precipitation; damage process Available at various institutes of the ASCR
HIGH - TEMPERATURE CREEP BEHAVIOUR OF CAST COBALT-BASE SUPERALLOYS

Two cast and heat-treated NbC and TaC – strengthened cobalt superalloys have been developed for a precision casting of spinner discs for glass wool industry. In this work constant load creep tests in ...

Dvořák, Jiří; Král, Petr; Kvapilová, Marie; Hrbáček, Karel; Sklenička, Václav
Ústav fyziky materiálů, 2018

HYDROGEN SORPTION BEHAVIOR OF CHOSEN BINARY MAGNESIUM-CONTAINING INTERMETALLICS
Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
2018 - English
Hydrogen absorption in chosen binary Mg-X (X-Al, Ga, In, Si and Sn) intermetallics was studied. These compounds are prospective as additives in other Mg-based hydrogen storage materials. From this point of view it is desirable to know the hydrogen solubility in Mg-X and their resistivity against hydride formation. The present study was carried out at temperatures up to 623 K. Keywords: Hydrogen storage; magnesium alloys; Mg-based intermetallics Available at various institutes of the ASCR
HYDROGEN SORPTION BEHAVIOR OF CHOSEN BINARY MAGNESIUM-CONTAINING INTERMETALLICS

Hydrogen absorption in chosen binary Mg-X (X-Al, Ga, In, Si and Sn) intermetallics was studied. These compounds are prospective as additives in other Mg-based hydrogen storage materials. From this ...

Čermák, Jiří; Král, Lubomír; Roupcová, Pavla
Ústav fyziky materiálů, 2018

Quantum-mechanical study of magnetic properties of superalloy nanocomposite phase Fe2AlTi
Slávik, Anton; Miháliková, Ivana; Friák, Martin; Všianská, Monika; Šob, Mojmír
2018 - English
The L21-structure Fe2AlTi intermetallic compound is one of the two phases identified in Fe-Al-Ti superalloy nanocomposites. Experimental data related to low-temperature magnetic properties of this Heusler compound indicate that magnetic moment is about 0.1 Bohr magneton per formula unit. In contrast, previous quantum-mechanical calculations predicted Fe2AlTi to have much higher magnetic moment, 0.9 Bohr magneton per formula unit. In order to solve this discrepancy between the theory and experiment we have performed a series of quantum-mechanical fix-spin-moment calculations and compared our results with those for non-magnetic state. It turns out that the total energy of the non-magnetic state is only by 10.73 meV/atom higher than that of the magnetic state. When applying Boltzmann statistics to this very small energy difference we predict that the non-magnetic state appears at non-zero temperatures with significant probabilities (for instance, 22.36 % at T = 100 K) and reduces the overall magnetic moment. As another mechanism lowering the magnetization we studied selected shape deformations, in particular trigonal shearing. Fe2AlTi exhibits a compression-tension asymmetry with respect to these strains and, for example, the strain 0.08 destabilizes the spin-polarized state, leaving the non-magnetic state as the only stable one. Keywords: Ab initio calculations; Fe-Al based superalloys; Fixed-spin-moment; Nanocomposites Available at various institutes of the ASCR
Quantum-mechanical study of magnetic properties of superalloy nanocomposite phase Fe2AlTi

The L21-structure Fe2AlTi intermetallic compound is one of the two phases identified in Fe-Al-Ti superalloy nanocomposites. Experimental data related to low-temperature magnetic properties of this ...

Slávik, Anton; Miháliková, Ivana; Friák, Martin; Všianská, Monika; Šob, Mojmír
Ústav fyziky materiálů, 2018

ESTIMATION OF EQUILIBRIUM HYDROGEN PRESSURE - A NEW METHOD
Čermák, Jiří; Král, Lubomír
2018 - English
A new method is proposed to estimation of hydrogen pressure in equilibrium with hydride phase in a hydrogen\nstorage material. It is applicable both for hydrogen absorption and desorption in cases where the hydride phase\nis formed by nucleation and growth mechanism. The proposed method saves considerably the experimental\ntime replacing the conventional time consuming measurement of pressure-composition isotherms, the so\ncalled PCT curves. The proposed evaluation procedure is illustrated using hydrogen chemi-sorption at\ntemperatures 623 K, 573 K and 523 K in chosen hydrogen storage alloys Mg-Si-C, Mg-Li-C and Mg-Na-C. Keywords: Hydrogen storage; magnesium; new method Available at various institutes of the ASCR
ESTIMATION OF EQUILIBRIUM HYDROGEN PRESSURE - A NEW METHOD

A new method is proposed to estimation of hydrogen pressure in equilibrium with hydride phase in a hydrogen\nstorage material. It is applicable both for hydrogen absorption and desorption in cases ...

Čermák, Jiří; Král, Lubomír
Ústav fyziky materiálů, 2018

MICROSTRUCTURE AND COMPOSITION OF FINE PARTICLES RELEASED BY CAR BRAKING
Švábenská, Eva; Roupcová, Pavla; Pizúrová, Naděžda; Schneeweiss, Oldřich
2018 - English
Vehicular traffic is connected with large volume of fine particles released during brake processes of cars. Our research is focused on the phase, structure and chemical analysis of the fine particles taken from some car brake parts by their services. The information on structure and phase composition was obtained by X-Ray Powder Diffraction, Mossbauer Spectroscopy, scanning electron microscopy with EDX and transmission electron microscopy. The results of the wear debris analysis are compared with original brake materials components. Most of recognized particles are based mainly on iron oxides. Wear brake particles are discussed in the relation to the potential risk to the environment and human health. Keywords: wear; Nanoparticles; wear debris; environment Available at various institutes of the ASCR
MICROSTRUCTURE AND COMPOSITION OF FINE PARTICLES RELEASED BY CAR BRAKING

Vehicular traffic is connected with large volume of fine particles released during brake processes of cars. Our research is focused on the phase, structure and chemical analysis of the fine particles ...

Švábenská, Eva; Roupcová, Pavla; Pizúrová, Naděžda; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2018

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases