Number of found documents: 1006
Published from to

Characterization of Ta-B-C nanostructured hard coatings
Buršík, Jiří; Buršíková, V.; Souček, P.; Zábranský, L.; Vašina, P.
2017 - English
Microstructure and mechanical properties of Ta-B-C nanocrystalline layers prepared by magnetron sputtering were studied. DC magnetron sputtering was used to prepare thin layers on rotated substrates. Various deposition parameters were tested. Microstructure of layers was studied by means of scanning and transmission electron microscopy on thin lamellar cross sections prepared using a focussed ion beam. Both undisturbed layers and the volume under relatively large indentation prints (load of 1 N) were observed. The microstructure observations were correlated with mechanical properties characterized by means of nanoindentation experiments in both the static and the dynamic loading regime. Elastic modulus, indentation hardness and fracture resistance of prepared nanostructured coatings were evaluated and discussed. Keywords: coating; nanostructure; analytical electron microscopy Available at various institutes of the ASCR
Characterization of Ta-B-C nanostructured hard coatings

Microstructure and mechanical properties of Ta-B-C nanocrystalline layers prepared by magnetron sputtering were studied. DC magnetron sputtering was used to prepare thin layers on rotated substrates. ...

Buršík, Jiří; Buršíková, V.; Souček, P.; Zábranský, L.; Vašina, P.
Ústav fyziky materiálů, 2017

Subsized Specimens for Fracture Resistance Characterisation Including Transferability Issues
Dlouhý, Ivo; Stratil, Luděk; Šiška, Filip
2017 - English
The contribution is focused on characterization of methods enabling to apply small/subsized specimens for fracture resistance characterization. The applied methods are divided into transition region and upper shelf region. The approaches used in the upper shelf region represent at the same time methods applicable for ductile materials without transition. Relating to subsized samples two basic approaches are applicable: (i) miniaturized samples based on common standard ones and (ii) specific specimens/methods, e.g. small punch test etc. The results described in the paper belong to the first group. For interpretation of data generated under low constraint conditions toughness scaling models and master curve approached are commented. In ductile region, either the sample used generate valid toughness characteristics, or, if not, there is no way how to correct measured data except damage quantification through micromechanical models. Keywords: Fracture toughness; Crack resistance curve; Transferability; Crack tip constraint; Subsized specimen Available at various institutes of the ASCR
Subsized Specimens for Fracture Resistance Characterisation Including Transferability Issues

The contribution is focused on characterization of methods enabling to apply small/subsized specimens for fracture resistance characterization. The applied methods are divided into transition region ...

Dlouhý, Ivo; Stratil, Luděk; Šiška, Filip
Ústav fyziky materiálů, 2017

Fracture-mechanics behaviour of ceramic foam with macroscopic stress concentrator upon the tensile test
Ševeček, O.; Majer, Z.; Bertolla, Luca; Chlup, Zdeněk; Kotoul, M.
2017 - English
The work investigates an influence of the macroscopic stress concentrator inside the ceramic open cell foam structure on the fracture-mechanics response of the foam upon the tensile test. As the concentrator, the central crack/rectangular notch was taken into account. The influence of the crack/notch length and width on the stress concentration ahead the concentrator tip was assessed using the simplified FE beam element based model with irregular cells simulating the real ceramic foam structure. Average principal stresses calculated on set of struts ahead the crack/notch tip were compared with average stresses in the intact structure. It was found that the ratio of these stresses increases linearly with the crack length. The stress concentration ratio is slightly lower in case of thick rectangular notch than in case of a thin crack. Furthermore, the failure load leading to complete fracture of the studied specimens, subjected to the tensile loading, were calculated using the same model. It is shown that the difference factor between the critical fracture force in case of structure without concentrator and with concentrator is very close to the concentration factor calculated from the average stresses on particular struts in the region in front of the concentrator tip.\n Keywords: Fracture-mechanics; ceramic foam; tensile test Available at various institutes of the ASCR
Fracture-mechanics behaviour of ceramic foam with macroscopic stress concentrator upon the tensile test

The work investigates an influence of the macroscopic stress concentrator inside the ceramic open cell foam structure on the fracture-mechanics response of the foam upon the tensile test. As the ...

Ševeček, O.; Majer, Z.; Bertolla, Luca; Chlup, Zdeněk; Kotoul, M.
Ústav fyziky materiálů, 2017

Prediction of the Traction Separation Law of Ceramics Using Iterative Finite Element Modelling
Kozák, Vladislav; Chlup, Zdeněk; Padělek, P.; Dlouhý, Ivo
2017 - English
Specific silicon nitride ceramics, the influence of the grain size and orientation on the bridging mechanisms was found. In ceramic matrix composites, crack-bridging mechanisms can provide substantial toughness enhancement coupled with the same and/or increased strength. The prediction of the crack propagation through interface elements based on the fracture mechanics approach and cohesive zone model is investigated. From a number of damage concepts the cohesive models seem to be especially attractive for the practical applications. Within the standard finite element package Abaqus a new finite element has been developed; it is written via the UEL (user’s element) procedure. Its shape can be modified according to the experimental data for the set of ceramics and composites. The element seems to be very stable from the numerical point a view. The shape of the traction separation law for four experimental materials is estimated via the iterative procedure based on the FEM modeling and experimentally determined displacement in indentation experiments, J-R curve is predicted and stability of the bridging law is tested. Keywords: cohesive zone model; Si3N4 composite; finite element user’s procedure Available at various institutes of the ASCR
Prediction of the Traction Separation Law of Ceramics Using Iterative Finite Element Modelling

Specific silicon nitride ceramics, the influence of the grain size and orientation on the bridging mechanisms was found. In ceramic matrix composites, crack-bridging mechanisms can provide substantial ...

Kozák, Vladislav; Chlup, Zdeněk; Padělek, P.; Dlouhý, Ivo
Ústav fyziky materiálů, 2017

LCF behaviour of 301LN steel: coarse-grained vs. UFG-bimodal structure
Man, Jiří; Chlupová, Alice; Kuběna, Ivo; Kruml, Tomáš; Man, O.; Järvenpää, A.; Karjalainen, L. P.; Polák, Jaroslav
2017 - English
Low-cycle fatigue (LCF) behaviour of metastable austenitic 301LN steel with different grain sizes – coarse-grained (14 µm) and UFG (1.4 µm) with a grain bimodality – produced by reversion annealing (RA) was investigated. Symmetrical push-pull LCF tests were conducted on flat sheet specimens at room temperature with constant strain rate of 2×10–3 s–1 and constant total strain amplitude ranging from 0.4% to 0.8%. After completion of fatigue tests a ferritescope was adopted for quantitative assessment of volume fraction of deformation induced martensite (DIM). Microstructural changes, distribution and morphology of DIM in the volume of material were characterized at different scales by colour etching, TEM and EBSD techniques. Experimental data on microstructural changes are confronted with the stress-strain response and with the chemical heterogeneity present in the material. Keywords: low cycle fatigue; 301LN austenitic stainless steel; UFG microstructure; reversion annealing; deformation induced martensite Available at various institutes of the ASCR
LCF behaviour of 301LN steel: coarse-grained vs. UFG-bimodal structure

Low-cycle fatigue (LCF) behaviour of metastable austenitic 301LN steel with different grain sizes – coarse-grained (14 µm) and UFG (1.4 µm) with a grain bimodality – produced by reversion annealing ...

Man, Jiří; Chlupová, Alice; Kuběna, Ivo; Kruml, Tomáš; Man, O.; Järvenpää, A.; Karjalainen, L. P.; Polák, Jaroslav
Ústav fyziky materiálů, 2017

HYDROGENATION PROPERTIES OF Mg-Al-Ti-Zr-C COMPOSITE
Král, Lubomír; Čermák, Jiří; Roupcová, Pavla
2017 - English
The improvement of hydrogen storage properties of ball-milled Mg-Al-Ti-Zr-C composite was studied in this\npaper. It has been previously shown, that the addition of Ti, Zr, Al and C improves storage properties of Mg.\nThis beneficial effect of additives upon hydrogen storage properties can be explained by catalysis by the\nnanoparticles rich in Ti, Zr or Al located on the surface of Mg grains. They provide effective pathways for the\nhydrogen diffusion into the MgH2. The morphological and microstructural characteristics were investigated by\nscanning electron microscope Tescan Lyra 3 and by X-ray diffraction. The hydrogen sorption was measured\nby Sieverts method using Setaram PCT-Pro device.\nStudied experimental composite absorbed 4.2 wt.% H 2 at 573 K and 3 wt.% H 2 at 523K within 10 min. The\nhydrogen storage capacity of the composite was about 4.6% wt.% H 2 and 4.2% wt.% H 2 at 573K and 523K,\nrespectively. Keywords: Hydrides; hydrogen storage; catalysis; hydrogen; Mg-alloys Available at various institutes of the ASCR
HYDROGENATION PROPERTIES OF Mg-Al-Ti-Zr-C COMPOSITE

The improvement of hydrogen storage properties of ball-milled Mg-Al-Ti-Zr-C composite was studied in this\npaper. It has been previously shown, that the addition of Ti, Zr, Al and C improves storage ...

Král, Lubomír; Čermák, Jiří; Roupcová, Pavla
Ústav fyziky materiálů, 2017

Nanoscale phases on surface Fe-6Si magnetic sheets
Švábenská, Eva; Roupcová, Pavla; Král, Lubomír; Bulín, Tomáš; Vondráček, Martin; Foldyna, Josef; Čechal, J.; Schneeweiss, Oldřich
2017 - English
Analysis of the nanoscale phases which appear on the surface Fe-6Si samples were carried out after the various treatments – grinding and etching, annealing, and water jet abrasion. The basic information on structure, chemical and phase composition was obtained by X-Ray Powder Diffraction (XRD), Scanning Electron Microscopy with EDX, Glow Discharge Optical Emission Spectrometry (GDOES), Mössbauer Spectroscopy and X-ray Photoelectron Spectrometry (XPS). The results show high stability of the surface phase composition after the mechanical and heat treatments. Results obtained from the surface analysis in micrometer depth (XRD, EDX, GDOES) do not show any changes after the different treatments. Iron oxides were detected in XPS and conversion electron Mössbauer spectra (CEMS) which analyze the surface composition in a nanometer scale. In addition to, fine changes in atomic ordering on the surface can be observed after mechanical and heat treatments in the CEMS spectra. Keywords: Fe-Si alloy; surface modification; nanostructure Available at various institutes of the ASCR
Nanoscale phases on surface Fe-6Si magnetic sheets

Analysis of the nanoscale phases which appear on the surface Fe-6Si samples were carried out after the various treatments – grinding and etching, annealing, and water jet abrasion. The basic ...

Švábenská, Eva; Roupcová, Pavla; Král, Lubomír; Bulín, Tomáš; Vondráček, Martin; Foldyna, Josef; Čechal, J.; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2017

CHANGES IN ELECTRICAL STEEL SHEETS INDUCED BY HEAT TREATMENT
Bulín, Tomáš; Švábenská, Eva; Hapla, Miroslav; Ondrušek, C.; Schneeweiss, Oldřich
2017 - English
Surface coating of electrical steel sheets is very important due to minimizing eddy current losses in electrical machines. The quality of coating can differ according to the composition. The coating layer has limited heat stability and after crossing of the guaranteed temperature it can be significantly degraded and its insulation properties may change importantly. The aim of this study is to describe changes in parameters of magnetic behavior of the non-oriented Si electrical steel sheet due to degradation of the coating by annealing in air. The parameters were acquired from the measuring of magnetic hysteresis loops on two types of samples with different excitation. The basic information on structure was obtained by optical microscopy. Acquired data are compared between samples with the damaged coating layer by annealing and the original coating layer. The results are discussed from the point of view of the possibility of using sheets with damaged insulation in electrical machines. Keywords: Surface coating; magnetic properties; annealing; degradation Available at various institutes of the ASCR
CHANGES IN ELECTRICAL STEEL SHEETS INDUCED BY HEAT TREATMENT

Surface coating of electrical steel sheets is very important due to minimizing eddy current losses in electrical machines. The quality of coating can differ according to the composition. The coating ...

Bulín, Tomáš; Švábenská, Eva; Hapla, Miroslav; Ondrušek, C.; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2017

ON THE ENERGY RELEASE RATE OF THE CRACK EMANATING FROM THE INCLUSION INTERPHASE
Profant, T.; Hrstka, M.; Klusák, Jan; Kersner, Z.
2017 - English
The problem of the crack emanating from the interphase region of the circular inclusion is investigated. The problem combines an application of dislocation distribution technique for a crack modelling and the method of boundary integral equations to approximate the loading along the boundary of the domain containing an inclusion. The topological derivative method provides the combination of both approaches and results to the evaluation of the energy release rate of the arbitrary oriented microcrack emanating from the inclusion and matrix interphase. The fundamental solution intended to the boundary integral method such as the continuously distributed dislocation technique is based on the application of Muschelishvili complex potentials in the form of the Laurent series. The coefficients of the series are evaluated from the compatibility conditions along the interfaces of inclusion, interface and matrix. Keywords: Microcrack; Inclusion; Interphase; Singular integral equation; Dislocation distribution technique; Complex potentials Available at various institutes of the ASCR
ON THE ENERGY RELEASE RATE OF THE CRACK EMANATING FROM THE INCLUSION INTERPHASE

The problem of the crack emanating from the interphase region of the circular inclusion is investigated. The problem combines an application of dislocation distribution technique for a crack modelling ...

Profant, T.; Hrstka, M.; Klusák, Jan; Kersner, Z.
Ústav fyziky materiálů, 2017

LOW CYCLE FATIGUE BEHAVIOR AND FATIGUE CRACK INITIATION IN MAR-M247 AT 700 °C
Šulák, Ivo; Obrtlík, Karel; Hrbáček, K.
2017 - English
The second generation nickel-based superalloy MAR-M247 offers a satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that are required for application at elevated temperatures in hostile environments. The microstructure consists mainly of the face centred cubic γ matrix and ordered γ´ strengthening precipitates (L12 crystal structure). The present work focuses on low cycle fatigue (LCF) behaviour of polycrystalline nickel-based superalloy MAR-M247 at high temperature. LCF tests were conducted on cylindrical specimens in a symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 700 °C in ambient air. Cyclic stress-strain curves and fatigue life curves in the representation of plastic strain amplitude vs. stress amplitude and stress amplitude vs. the number of cycles to failure, respectively, were plotted and compared with data obtained on Inconel 713LC. Special attention was paid to the investigation of crack initiation in MAR-M247 during low cycle fatigue. Crack initiation sites were studied by means of scanning electron microscopy (SEM) in dual beam microscope TESCAN LYRA 3 XMU FESEM equipped with focus ion beam (FIB). Specimens’ surface observations revealed the formation of pronounced surface relief indicating localisation of plastic deformation. Observations in transmission electron microscope (TEM) confirmed localisation of cyclic plastic deformation in persistent slip bands along {111} slip planes. Fractographic analysis revealed fatigue crack initiation sites. Fatigue crack propagation in stage I was typical of smooth facets up to 500 μm long. Keywords: Nickel-based superalloy; cyclic stress-strain curve; Fatigue life; fatigue crack initiation; focus ion beam Available at various institutes of the ASCR
LOW CYCLE FATIGUE BEHAVIOR AND FATIGUE CRACK INITIATION IN MAR-M247 AT 700 °C

The second generation nickel-based superalloy MAR-M247 offers a satisfying combination of fatigue and creep properties and oxidation and corrosion resistance that are required for application at ...

Šulák, Ivo; Obrtlík, Karel; Hrbáček, K.
Ústav fyziky materiálů, 2017

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