Number of found documents: 906
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Effect of residual elements on quality of pure zinc
Luptáková, Natália; Pešlová, F.; Stodola, J.
2014 - English
The paper deals with the nature and morphology of the input material for the production of metallic zinc which is used in the production of ZnO through indirect pyrometallurgical processes. The input material is the key parameter in the production of high-quality zinc oxide. For the prediction of complex production process when problematic situation may occur, the systematic analysis of the input zinc raw materials is needed. Undesirable phases in the feedstock can be identified through profound recognition of the source material and the nature of its microstructure. Chemical composition of zinc metal and zinc additives helps to detect the phases occurring in the matrix. Undesirable phases in the feedstock can form (with zinc and other elements) hard and brittle compounds. If these compounds diffuse into the lining during thermal processes, they become the cause of stress in metallurgical ceramics. The emergence of these chemical reactions may subsequently affect the entire metallurgical zinc smelting process. From the microstructure viewpoint, the heterogeneity of grain size, various morphology of intermediate phases, their layout, arrangement, etc. can be expected. The results obtained by analysis are used to minimize waste - zinc slag and to eliminate the conditions which enable the formation of the undesired product, thereby increasing the productivity of the zinc oxide production. Keywords: zinc; metallurgical process; phases; residual elements Available at various institutes of the ASCR
Effect of residual elements on quality of pure zinc

The paper deals with the nature and morphology of the input material for the production of metallic zinc which is used in the production of ZnO through indirect pyrometallurgical processes. The input ...

Luptáková, Natália; Pešlová, F.; Stodola, J.
Ústav fyziky materiálů, 2014

Crack under biaxial loading: Two-parameter description
Seitl, Stanislav; Bermejo, C. S.
2014 - English
A two-parameter approach for description of stress field for isotropic materials under biaxial loading was proposed in this contribution. From the results, it was found that analysis using the two-parameter fracture mechanics is an effective way to evaluate stress fields under biaxial stress. Keywords: Biaxial loading; T-stress; stress intensity factor; crack Available at various institutes of the ASCR
Crack under biaxial loading: Two-parameter description

A two-parameter approach for description of stress field for isotropic materials under biaxial loading was proposed in this contribution. From the results, it was found that analysis using the ...

Seitl, Stanislav; Bermejo, C. S.
Ústav fyziky materiálů, 2014

NUMERICAL ESTIMATION OF MICRO-CRACK PATHS IN POLYMER PARTICULATE COMPOSITE
Majer, Z.; Náhlík, Luboš
2014 - English
Determination of composite mechanical behavior is one of important part during the composite tailoring. The aim of the present work was to estimate a micro-crack behavior in a polymer particulate composite. The composite was investigated by means of the finite element method -using ANSYS software. A two-dimensional three-phase finite element model was developed to analyze the crack growth behavior. The assumptions of the linear elastic fracture mechanics were considered and the Maximum Tangential Stress (MTS) criterion was used to predict the direction of the crack propagation. The effect of the elastic modulus of the interphase on the micro-crack propagation was investigated. The properties of matrix and particles were taken from experiment. It was shown that the interphase properties influence the stress intensity factor KI as well as the micro-crack paths. The results of this paper can contribute to a better understanding of the micro-crack propagation in particulate composites with respect to the interphase. Keywords: Polymer Composite; Fracture Mechanics; Interphase; Finite Element Method Available at various institutes of the ASCR
NUMERICAL ESTIMATION OF MICRO-CRACK PATHS IN POLYMER PARTICULATE COMPOSITE

Determination of composite mechanical behavior is one of important part during the composite tailoring. The aim of the present work was to estimate a micro-crack behavior in a polymer particulate ...

Majer, Z.; Náhlík, Luboš
Ústav fyziky materiálů, 2014

CARBON DIFFUSION IN CARBON-SUPERSATURATED 9CR-1MO STEEL: ANOMALOUS TEMPERATURE DEPENDENCE OF CARBON DIFFUSIVITY
Čermák, Jiří; Král, Lubomír
2014 - English
Carbon diffusion was studied in temperature interval 573 - 1073 K in carbon-supersaturated surface layer of 9Cr–1Mo steel P91 and in model Fe-15Cr binary alloy. Extremely low carbon diffusion coefficient D (by 3 orders of magnitude lower than the value D eq in material with equilibrium carbon concentration) was observed in carburized surface region of Fe-15Cr. Similar results were obtained for P91 above the temperature T n ~ 800 K. However, below T n , the values of D measured in P91 increased and approached the value of D eq . It seems that the non-Arrhenius behaviour of P91 steel around T n may be ascribed to the α → α + α’ phase decomposition. Possible effect of nitrogen upon the low-temperature increase in D in P91 steel was excluded. Keywords: Diffusion; Carbon; phase decomposition; Carbon-supersaturation; Cr-Mo steels Available at various institutes of the ASCR
CARBON DIFFUSION IN CARBON-SUPERSATURATED 9CR-1MO STEEL: ANOMALOUS TEMPERATURE DEPENDENCE OF CARBON DIFFUSIVITY

Carbon diffusion was studied in temperature interval 573 - 1073 K in carbon-supersaturated surface layer of 9Cr–1Mo steel P91 and in model Fe-15Cr binary alloy. Extremely low carbon diffusion ...

Čermák, Jiří; Král, Lubomír
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; Karjalalinen, L.P.
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 thermomechanical treatment. Fatigue life curves were obtained and compared for both coarse-grained and ultrafine- 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; reversion annealing; phase transformation 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. ...

Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Škorík, Viktor; Karjalalinen, L.P.
Ústav fyziky materiálů, 2014

IN-SITU HIGH TEMPERATURE LOW CYCLE FATIGUE STUDY
Petrenec, M.; Polák, Jaroslav; Šamořil, T.; Dluhoš, J.; Obrtlík, Karel
2014 - English
In-situ Low Cycle Fatigue test (LCF) at temperature 635 °C have been performed in Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction analysis (EBSD) on a small dog-bone-shaped specimen of cast Inconel 713LC superalloy. The aim of the work was to study early stage fatigue damage at high temperature by the observations of the characteristic surface relief evolution and crystallographic characterization changes by EBSD. The detail of slip bands shape was checked by FIB and AFM microscopes. The LCF test was conducted on GATAN stage with pre tilted position and constant stress amplitude of total cycle number of 20. The relief produced in the first cycle determines the other locations of the localized cyclic slip to the primary slip planes (111). The relief was modified in the next cycles but without forming additionally new slip traces in the primary system. Based on EBSD analysis before and after LCF, the orientation of two grains was changed which caused activation of second slip system. The damage mechanism evolution is closely connected with the cyclic strain localization to the persistent slip bands where the fatigue cracks were initiated. Keywords: In-situ; SEM; high temperature; fatigue; superalloy Available at various institutes of the ASCR
IN-SITU HIGH TEMPERATURE LOW CYCLE FATIGUE STUDY

In-situ Low Cycle Fatigue test (LCF) at temperature 635 °C have been performed in Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction analysis (EBSD) on a small ...

Petrenec, M.; Polák, Jaroslav; Šamořil, T.; Dluhoš, J.; Obrtlík, Karel
Ústav fyziky materiálů, 2014

Modified compact tension test: The influence of the steel bars position
Holušová, Táňa; Seitl, Stanislav; Fernández-Canteli, A.
2014 - English
Testing and analysis of fatigue behavior of homogeneous materials, such as concrete or other cement based composites, are one major problem being studied in this scientific field. In this contribution, adaptation of the compact tension test, well known its use in the testing of metallic materials, is pursued for crack propagation rate measurement on cement based composites using cylindrical specimens. In particular, the influence of the steel bars position on the fracture parameters is studied in the modified compact tension test. The numerical study is performed by ATENA 2D. The results are compared by Load-COD diagrams and the variation of the fracture parameters values is discussed. Keywords: Modified compact tension test; Concrete; Fracture parameters of concrete; FEM Available at various institutes of the ASCR
Modified compact tension test: The influence of the steel bars position

Testing and analysis of fatigue behavior of homogeneous materials, such as concrete or other cement based composites, are one major problem being studied in this scientific field. In this ...

Holušová, Táňa; Seitl, Stanislav; Fernández-Canteli, A.
Ústav fyziky materiálů, 2014

THE EFFECT OF THRESHOLD VALUE ON THE RESIDUAL FATIGUE LIFETIME OF RAILWAY AXLES
Pokorný, Pavel; Náhlík, Luboš; Hutař, Pavel
2014 - English
The fatigue failure of railway axles could have unaccepted consequences. Because of safe operation, it is important to determine the residual fatigue lifetime. The railway axle could contain some cracks either from manufacturing process or from previous service operation. Present defectoscopy can reliably detect only relatively long cracks (longer than 2 mm), see [1]. In other words, there is a risk that the existing crack is not detected by defectoscopy. For conservative establishment of the residual fatigue lifetime the crack, which could be not detected by defectoscopy, must be considered. This paper deals with an effect of the threshold value of fatigue crack propagation on the residual fatigue lifetime of railway axles. Two very commonly used materials for railway axles EA1N and EA4T steels are considered. The results of this paper could be used for safer operation of railway axles. Keywords: railway axle; threshold value; fatigue crack; residual fatigue lifetim Available at various institutes of the ASCR
THE EFFECT OF THRESHOLD VALUE ON THE RESIDUAL FATIGUE LIFETIME OF RAILWAY AXLES

The fatigue failure of railway axles could have unaccepted consequences. Because of safe operation, it is important to determine the residual fatigue lifetime. The railway axle could contain some ...

Pokorný, Pavel; Náhlík, Luboš; Hutař, Pavel
Ústav fyziky materiálů, 2014

Estimation of critical values for crack initiation from sharp V-notches
Náhlík, Luboš; Štegnerová, Kateřina; Hutař, Pavel
2014 - English
Abstract: The aim of the paper is to estimate a critical value of an applied stress for a crack initiation from sharp tip of the V-notch using a procedure based on linear elastic fracture mechanics (LELM). The V-notch represents singular stress concentrator with the stress singularity exponent different from 0.5, therefore the generalized form of LELM for stress distribution description in the vicinity of the sharp V-notch was used. The stress singularity exponent depends on the V-notch opening angle, in general. A stability criterion based on the average value of the tangential stress component across a critical distance d from the V-notch tip is used in the paper. Resultant values of the critical applied stress are compared with experimental data. Keywords: Failure initiation; stress singularity; V-notch; generalized stress intensity factor Available at various institutes of the ASCR
Estimation of critical values for crack initiation from sharp V-notches

Abstract: The aim of the paper is to estimate a critical value of an applied stress for a crack initiation from sharp tip of the V-notch using a procedure based on linear elastic fracture mechanics ...

Náhlík, Luboš; Štegnerová, Kateřina; Hutař, Pavel
Ústav fyziky materiálů, 2014

EFFECT OF HIP ON LOW CYCLE FATIGUE OF MAR-M247 AT 900°C
Šulák, Ivo; Obrtlík, Karel; Škorík, Viktor; Hrbáček, K.
2014 - English
Polycrystalline nickel-base superalloy MAR-M247 is used for high temperature applications requiring excellent combination of fatigue properties, creep resistance and surface stability. These superior high temperature characteristics derive from the microstructure which habitually consists of face centred cubic matrix γ and precipitate γ´ (L12 type ordered structure). In the present work, the high temperature low cycle fatigue behaviour of cast nickel-base superalloy MAR-M247 in as received condition and in hot isostatically pressed (HIP) condition was studied. The microstructure of the materials is characterized by dendritic grains, carbides and casting defects. Distribution and size of defects in both materials were studied. Isothermal low cycle fatigue (LCF) tests were performed on cylindrical specimens under total strain control at 900°C in air. Cyclic stress–strain response and fatigue life of both materials were assessed. Beneficial effects of HIP process on cyclic stress-strain and fatigue life curves are discussed. Keywords: MAR-M-247; High temperature; Low cycle fatigue Available at various institutes of the ASCR
EFFECT OF HIP ON LOW CYCLE FATIGUE OF MAR-M247 AT 900°C

Polycrystalline nickel-base superalloy MAR-M247 is used for high temperature applications requiring excellent combination of fatigue properties, creep resistance and surface stability. These superior ...

Šulák, Ivo; Obrtlík, Karel; Škorík, Viktor; Hrbáček, K.
Ústav fyziky materiálů, 2014

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