Number of found documents: 906
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Application of simplified mechanical model for description of specimen size effect on resistance against stable tearing
Stratil, Luděk; Šiška, Filip; Hadraba, Hynek; Dlouhý, Ivo
2014 - English
This contribution deals with a size effect on J-R curve of three points bend specimens made from Eurofer97 steel and with possibilities to predict the specimen behaviour between various specimen sizes. To do it, a simplified mechanical model proposed by Schindler is applied to obtained tests results in order to predict observed size effect on J-R curve. Keywords: size effect; three point bend; scalinq laws; Eurofer97; J-R curve Available at various institutes of the ASCR
Application of simplified mechanical model for description of specimen size effect on resistance against stable tearing

This contribution deals with a size effect on J-R curve of three points bend specimens made from Eurofer97 steel and with possibilities to predict the specimen behaviour between various specimen ...

Stratil, Luděk; Šiška, Filip; Hadraba, Hynek; Dlouhý, Ivo
Ústav fyziky materiálů, 2014

Applicability of small punch test to determine the material mechanical properties at room and high temperatures
Dymáček, Petr; Ječmínka, M.
2014 - English
The paper is focused on testing of mechanical properties by small punch test (SPT) and comparison of these properties with mechanical properties obtained by conventional tensile tests of steels P92 and AISI 316L. The yield stress and ultimate tensile stress obtained by SPT at constant deflection rate (SPT-CDR) were evaluated. Values of initial stress and residual stress were evaluated from relaxation small punch test (SPT-R). Mechanical properties obtained by SPT-CDR and SPT-R are compared with mechanical properties obtained by conventional tensile test and relaxation tensile test, respectively. Modified empirical relationships for an assessment of tensile test properties from quantities determined by small punch test are proposed. Good agreement of results of SPT-R and relaxation tensile test is shown by their comparison. Keywords: small punch test; stress relaxation Available at various institutes of the ASCR
Applicability of small punch test to determine the material mechanical properties at room and high temperatures

The paper is focused on testing of mechanical properties by small punch test (SPT) and comparison of these properties with mechanical properties obtained by conventional tensile tests of steels P92 ...

Dymáček, Petr; Ječmínka, M.
Ústav fyziky materiálů, 2014

The Gurson-Tvergaard-Needleman model calibration from sub-size test specimens by size corresponding to the half of Charpy specimen
Stratil, Luděk; Šiška, Filip; Hadraba, Hynek; Dlouhý, Ivo
2014 - English
The paper deals with a utilization of miniaturized tensile specimens for purposes of local approach application from limited amount of test material. The motivation for application of those miniaturized specimens is the utilization of volume of test material corresponding to the half of Charpy specimen. The tensile testing of miniaturized specimens was conducted at room temperature in ductile regime of the Eurofer97 steel followed by detailed fractography and quantitative analysis of micromechanism of damage. The parameters of Gurson-Tvergaard-Needleman micromechanical model of ductile fracture were calibrated. Except for the slight differences in strength and deformation characteristics no other differences between two sizes of tensile specimens were found. The calibrated sets of parameters of GTN model using the same element size were very similar. The application of different calibrated sets of GTN model parameters for simulation of damage in cracked specimen (R-curve) is sensitive to the element size and needs its calibration. Keywords: GTN model; miniaturized specimens; fractography analysis; ductile damage Available at various institutes of the ASCR
The Gurson-Tvergaard-Needleman model calibration from sub-size test specimens by size corresponding to the half of Charpy specimen

The paper deals with a utilization of miniaturized tensile specimens for purposes of local approach application from limited amount of test material. The motivation for application of those ...

Stratil, Luděk; Šiška, Filip; Hadraba, Hynek; Dlouhý, Ivo
Ústav fyziky materiálů, 2014

Z-phase in Cr-Nb-N system studied by analytical electron microscopy
Buršík, Jiří; Kroupa, Aleš
2014 - English
In this work we study the Z-phase in model Cr-Nb-N alloys by means of analytical electron microscopy (SEM and TEM). Keywords: Cr-Nb-N system; SEM and TEM; EDX Available at various institutes of the ASCR
Z-phase in Cr-Nb-N system studied by analytical electron microscopy

In this work we study the Z-phase in model Cr-Nb-N alloys by means of analytical electron microscopy (SEM and TEM).

Buršík, Jiří; Kroupa, Aleš
Ústav fyziky materiálů, 2014

GRAIN REFINEMENT EFFECT ON FATIGUE PROPERTIES OF AUSTENITIC STAINLESS STEEL WITH DEFORMATION INDUCED MARTENSITE FORMATION
Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Škorík, Viktor; Karjalainen, J.
2014 - English
Fatigue properties of metastable austenitic 301LN steel with coarse and ultrafine-grained microstructures were investigated at ambient temperature and the effect of grain refinement was evaluated. Two different microstructural states of material were introduced by different annealing conditions during special thermo-mechanical treatment. Fatigue life curves were obtained and compared for both coarse-grained and ultra-fine-grained states of austenitic stainless steel. Magnetic measurements before, during and after cyclic loading were performed to reveal structural changes, i.e. formation of deformation-induced martensite. Relationship between microstructure refinement, phase composition and fatigue properties was discussed. Keywords: Fatigue; 301LN austenitic stainless steel; grain refinement Available at various institutes of the ASCR
GRAIN REFINEMENT EFFECT ON FATIGUE PROPERTIES OF AUSTENITIC STAINLESS STEEL WITH DEFORMATION INDUCED MARTENSITE FORMATION

Fatigue properties of metastable austenitic 301LN steel with coarse and ultrafine-grained microstructures were investigated at ambient temperature and the effect of grain refinement was evaluated. Two ...

Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Škorík, Viktor; Karjalainen, J.
Ústav fyziky materiálů, 2014

FRACTURE MECHANICS ASSESSMENT OF CRACKED WELDED POLYOLEFIN PIPES
Mikula, Jakub; Ševčík, Martin; Hutař, Pavel; Náhlík, Luboš
2014 - English
The aim of this paper is to present methodology for estimation of fracture mechanics parameters in polyolefin pipes with an axially oriented crack using three dimensional numerical analyses. Linear elastic fracture mechanics is used for description of fracture behavior. In the paper, three different variants of pipe weld with an internal axial semi-elliptical crack are studied. Numerical models correspond to a cracked pipe containing material nonhomogeneity in the welding area caused by welding process. A critical locations of the crack initiated along the pipe wall is found and the stress intensity factor for such cracks with real crack shape are numerically estimated in these critical locations. The methodology presented here can be used for estimation of residual lifetime of welded polymer pipes containing crack. Keywords: Polyolefin pipes; butt weld; stress intensity factor; numerical loading Available at various institutes of the ASCR
FRACTURE MECHANICS ASSESSMENT OF CRACKED WELDED POLYOLEFIN PIPES

The aim of this paper is to present methodology for estimation of fracture mechanics parameters in polyolefin pipes with an axially oriented crack using three dimensional numerical analyses. Linear ...

Mikula, Jakub; Ševčík, Martin; Hutař, Pavel; Náhlík, Luboš
Ústav fyziky materiálů, 2014

Microstructural Investigation and Mechanical Testing of an Ultrafine-grained Austenitic Stainless Steel
Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Karjalainen, L. P.
2013 - English
Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with considerably enhanced mechanical properties. Two different conditions of the thermomechanical treatment were adopted and resulting microstructures with different grain sizes were characterised by optical and high resolution scanning electron microscopy (SEM-FEG). Hardness measurements and tensile tests were performed to characterize mechanical properties. To reveal structural changes induced during thermomechanical treatment and during tensile tests a magnetic induction method was additionally applied. Experimental study validated the ability of the above special treatment to produce austenitic stainless steel with grain size about 1.4 m which exhibits tensile strength about 1000MPa while ductility remains on level about 60 %. The results obtained for both thermomechanical conditions are compared and the relationship between microstructure refinement, phase content and mechanical properties is discussed. Keywords: austenitic steel; ultra-fine grained microstructure; thermomechaical heart treatment; mechanical propeties; hardness Available at various institutes of the ASCR
Microstructural Investigation and Mechanical Testing of an Ultrafine-grained Austenitic Stainless Steel

Special thermomechanical treatment based on high degree deformation followed by reversion annealing was applied to 301LN austenitic stainless steel to achieve ultrafine-grained (UFG) structure with ...

Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Karjalainen, L. P.
Ústav fyziky materiálů, 2013

PREPARATION OF FE-TI COMPOSITES BY BALL MILLING
Roupcová, Pavla; Schneeweiss, Oldřich
2013 - English
The similar Ti-Fe powders were prepered from pure precursors as well as from splinters. The difference of structural and phase composition was determined by XRD and Mössbauer spectroscopy. Keywords: Ti-Fe; X-ray diffraction; hydrogen absorbing materials; Mössbauer spectroscopy Available at various institutes of the ASCR
PREPARATION OF FE-TI COMPOSITES BY BALL MILLING

The similar Ti-Fe powders were prepered from pure precursors as well as from splinters. The difference of structural and phase composition was determined by XRD and Mössbauer spectroscopy.

Roupcová, Pavla; Schneeweiss, Oldřich
Ústav fyziky materiálů, 2013

Comparison of Diffusion Coefficients in Initial Stages of Mutual Diffusion in Layered Structures Carbon/Ferrite and Carbon/Austenite for Chosen Alloys
Čermák, Jiří; Král, Lubomír
2013 - English
Coefficients of mutual carbon diffusion were measured at initial stages of diffusion for surface thin layer of carbon/ferrite and carbon surface layer/austenite. The aim of the study was to compare the diffusion characteristics obtained at the present strongly non-equilibrium case with those known for carbon mutual diffusion in cases where the carbon concentration does not exceed the solubility limit in the respective substrate. The second goal was to judge, whether the carbon diffusivity is determined by the structure of the substrate matrix (BCC or FCC). As examples of ferrite substrate, pure Fe and chromium steel P91 were chosen, as an example of austenite substrate, AISI316 was taken. It was obtained that – similar to nearequilibrium case – the carbon diffusion measured close to interface C/austenite is significantly lower compared to carbon diffusion near the C/ferrite. Values of carbon diffusion coefficients in cases C/Fe and C/P91 are close one to another. All carbon diffusion coefficients are much lower than those, reported for near-equilibrium conditions; they approach values measured in carbides. Keywords: Carbon; Initial stage of mutual diffusion; P91; AISI316 Available at various institutes of the ASCR
Comparison of Diffusion Coefficients in Initial Stages of Mutual Diffusion in Layered Structures Carbon/Ferrite and Carbon/Austenite for Chosen Alloys

Coefficients of mutual carbon diffusion were measured at initial stages of diffusion for surface thin layer of carbon/ferrite and carbon surface layer/austenite. The aim of the study was to compare ...

Čermák, Jiří; Král, Lubomír
Ústav fyziky materiálů, 2013

Initial Stage of Mutual Diffusion of Carbide in Iron
Čermák, Jiří; Král, Lubomír
2013 - English
Initial stage of mutual diffusion close to carbon/iron interface was investigated in the present work. SIMS technique of concentration profiles enabled to study the carbon redistribution in the very early stages, when the diffusion process occurs – at least partly – in regions, where the carbon concentration exceeds the carbon concentration limit. It was observed that carbon diffusion coefficients are much lower under such conditions, than in Fe matrix with equilibrium carbon concentration. The measured carbon diffusion coefficients approached values reported for carbon diffusion in carbides. Keywords: Carbon; Diffusion; Initial stage of mutual diffusion; SIMS Available at various institutes of the ASCR
Initial Stage of Mutual Diffusion of Carbide in Iron

Initial stage of mutual diffusion close to carbon/iron interface was investigated in the present work. SIMS technique of concentration profiles enabled to study the carbon redistribution in the very ...

Čermák, Jiří; Král, Lubomír
Ústav fyziky materiálů, 2013

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