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ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS
Ostapovets, Andriy
2015 - English
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and twin boundaries are usually oriented along invariant planes. However, non-invariant plane twin interfaces are also observed. Occurrence of such interfaces can be connected with interactions between twinning disconnections. Mechanisms of such interactions are discussed on the basis of atomistic simulations.
Keywords:
Twin boundaries; hcp; EAM potential
Available at various institutes of the ASCR
ATOMISTIC SIMULATIONS OF TWIN BOUNDARIES FACETING IN HCP MATERIALS
Deformation twinning is frequently observed in materials with hexagonal crystal lattice. It plays important role in plastic deformation of such materials. Twin regions have often lamellar shape and ...
MODIFIKOVANÁ ZKOUŠKA EXCENTRICKÝM TAHEM: VYHODNOCENÍ EXPERIMENTÁLNÍCH TESTŮ VÁLCOVÝCH TĚLES Z CEMENTOVÉHO KOMPOZITU
Holušová, T.; Lozano, M.; Komárková, T.; Kocáb, D.; Seitl, Stanislav
2015 - Czech
Modifikovaná zkouška excentrickým tahem (MCT) by mohla v budoucnu představovat stabilní zkoušku pro vyhodnocování lomově-mechanických parametrů nebo také únavového chování kompozitních materiálů jako je beton. Těleso pro MCT zkoušku s kruhovým průměrem může být snadno odebráno z jádrového vývrtu se zvolenou tloušťkou a velikostí průměru. Tato práce je zaměřena na vyhodnocení lomového chování MCT těles při statickém zatěžování a porovnání dvou různých uchycení do čelistí testovacího zařízení. Výsledky jsou prezentovány formou L-COD zatěžovacích digramů, tj. závislosti zatížení (L) měřeného v ose ocelových tyčí na velikosti otevření trhliny (COD). The modified compact tension test (MCT) might be in the future a stable test configuration for the evaluation of fracture-mechanics parameter or also a fatigue behavior of the composites materials such the concrete is. Core drilling can be employed to obtain specimens which are cylindrical in shape with the chosen thickness. This contribution focuses on the evaluation of MCT specimen fracture behavior during static tests and the comparison of two different fixing system of the test machine. The results are represented as L-COD diagrams (i.e. load vs. crack opening displacement measured on the loading axis.
Keywords:
Modified compact tension test; fracture parameters; composites; ARAMIS; L-COD
Available at various institutes of the ASCR
MODIFIKOVANÁ ZKOUŠKA EXCENTRICKÝM TAHEM: VYHODNOCENÍ EXPERIMENTÁLNÍCH TESTŮ VÁLCOVÝCH TĚLES Z CEMENTOVÉHO KOMPOZITU
Modifikovaná zkouška excentrickým tahem (MCT) by mohla v budoucnu představovat stabilní zkoušku pro vyhodnocování lomově-mechanických parametrů nebo také únavového chování kompozitních materiálů jako ...
Ab initio calculations of temperature dependent resistivity for transition metals
Wagenknecht, D.; Turek, Ilja; Carva, K.
2015 - English
The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The developed theory has been applied successfully to late transition metals (Fe, Ni, Rh, Pd, Pt).
Keywords:
electrical resistivity; temperature dependence; transition metals
Available at various institutes of the ASCR
Ab initio calculations of temperature dependent resistivity for transition metals
The effect of phonons on electrical resistivity has been simulated by considering random displacements of atomic nuclei from their equilibrium positions together with a frozen-potential approach. The ...
Effect of grit blasting surface treatment on high temperature low cycle fatigue life of Inconel 713LC
Šulák, Ivo; Obrtlík, Karel; Čelko, L.; Gejdoš, P.
2015 - English
This paper presents the results of high temperature low cycle fatigue tests carried out on Inconel 713LC. This polycrystalline nickel based superalloys is mainly used for high temperature applications such as disks, blades and vanes of gas turbine engines. These machine components are manufactured by investment casting and undergo a series of postcast processes to remove remnants of shells, oxides and other contaminants. Grit blasting is one of the most widely used and cheapest technology ensuring adequate cleaning of the surface and at the same time is used to treat the substrate surface prior to application of metalic bond coat and various protective coatings (like diffusion, overlay or thermall barier coatings). Low cycle fatigue tests were conducted on as-received and grit blasted material in fully reversed pull-push cycle in strain control mode with constant total strain amplitude and strain rate at 900 °C in air. Experimental data on fatigue life were evaluated and parameters of Baquin and Coffin-Manson curves were obtained for both tested materials. Specimen surface and cross sections of both treated and untreated materials were analysed prior to fatigue tests and also after testing by means of optical microscopy (OM), as well as scaning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and Vickers microhardness was measured. Fatigue degradation mechanisms was documented in both materials and negligible effect of grit blasting on low cycle parameters was discussed.
Keywords:
Grit blasting; Surface relief; Surface microhardnes; High temperature fatigue life; Inocel 713LC
Available at various institutes of the ASCR
Effect of grit blasting surface treatment on high temperature low cycle fatigue life of Inconel 713LC
This paper presents the results of high temperature low cycle fatigue tests carried out on Inconel 713LC. This polycrystalline nickel based superalloys is mainly used for high temperature ...
Analysis of nanoparticles released from the car brakes
Švábenská, Eva; Roupcová, Pavla; Schneeweiss, Oldřich
2015 - English
Our research is focused on the phase, structure and chemical analysis of the powder particles released by braking of cars from their brake components – discs and pads. The basic information on structure and phase composition was obtained by X-Ray Powder Diffraction, Mössbauer Spectroscopy and scanning electron microscopy with EDX. The results of the particle analysis are compared with materials used for manufacturing brake components and with the powder prepared by ball milling of the mixture of the pad composite and disk steel. Most of recognized nanoparticles are based on carbon, silica/silicates and iron oxides. Their effects on street environment are mentioned.
Keywords:
nanoparticles; wear debris; automotive brake
Available at various institutes of the ASCR
Analysis of nanoparticles released from the car brakes
Our research is focused on the phase, structure and chemical analysis of the powder particles released by braking of cars from their brake components – discs and pads. The basic information on ...
Thermo-mechanical and isothermal fatigue behavior of austenitic stainless steel AISI 316L
Škorík, Viktor; Šulák, Ivo; Obrtlík, Karel; Polák, Jaroslav
2015 - English
Many structural components of nuclear power plant systems are made of austenitic stainless steels. These structures undergo degradation by thermo-mechanical fatigue (TMF) caused by simultaneous cyclic straining and temperature cycling, particularly during start-up, shut-down and transient operations. The present work reports the cyclic deformation behavior and fatigue damage of austenitic stainless steel AISI 316L during TMF and isothermal fatigue (IF) testing in air. Total strain controlled in-phase TMF loading in the temperature range 200 - 600 °C and isothermal fatigue (IF) at 600 °C were performed. Hardening/softening curves, cyclic stress-strain response and fatigue life diagrams were obtained both for TMF and IF tests. Fatigue damage was documented using surface relief and fracture surface observations. Mean stress evolution and fatigue degradation data are employed to discuss the fatigue behavior of 316L steel both in TMF and IF regimes.
Keywords:
Thermo-mechanical fatigue (TMF); In-phase cycling (IP); Isothermal fatigue (IF); AISI 316L; Fatigue life
Available at various institutes of the ASCR
Thermo-mechanical and isothermal fatigue behavior of austenitic stainless steel AISI 316L
Many structural components of nuclear power plant systems are made of austenitic stainless steels. These structures undergo degradation by thermo-mechanical fatigue (TMF) caused by simultaneous cyclic ...
MAGNETIC AND TRANSPORT PROPERTIES OF 41CRMO4 STEEL
Bulín, T.; Hapla, Miroslav; Roupcová, Pavla; Ondrůšek, Č.; Schneeweiss, Oldřich
2015 - English
We have measured magnetic parameters and electrical resistivity of 41CrMo4 steel. It consist ferrite, Cr7C3 and Cr23C6 type of carbides. The\nmeasurements of temperature dependences of magnetic moments and electrical resistivity confirm phase stability of ferrite. The room temperature resistivity, saturation magnetization at room temperature, as well as AC measurements was measured. The power losses are strongly dependent on frequency and excitations.
Keywords:
41CrMo4 steel; magnetic properties; electrical resistivity
Available at various institutes of the ASCR
MAGNETIC AND TRANSPORT PROPERTIES OF 41CRMO4 STEEL
We have measured magnetic parameters and electrical resistivity of 41CrMo4 steel. It consist ferrite, Cr7C3 and Cr23C6 type of carbides. The\nmeasurements of temperature dependences of magnetic ...
IN-SITU HIGH TEMPERATURE LOW CYCLE FATIGUE STUDY OF SURFACE TOPOGRAPHY EVOLUTION IN NICKEL SUPERALLOY
Petrenec, M.; Polák, Jaroslav; Šamořil, T.; Dluhoš, J.; Obrtlík, Karel
2014 - English
In-situ Low Cycle Fatigue test (LCF) at temperature 635 degrees 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 OF SURFACE TOPOGRAPHY EVOLUTION IN NICKEL SUPERALLOY
In-situ Low Cycle Fatigue test (LCF) at temperature 635 degrees C have been performed in Scanning Electron Microscope (SEM) equipped with Electron Backscatter Diffraction analysis (EBSD) on a small ...
Analysis of slag material in the production of zinc oxide
Luptáková, Natália; Pešlová, F.
2014 - English
The given paper is closely connected with determination of character and morphology of slag generated in the production of ZnO. Hazardous situations relating to occurrence of these elements are hidden in their ability to create ternary eutectic formations and in terms of mechanical properties, they have ability to create quite fragile structure. The presence of oxygen as well as high temperature causes adhesion of ternary eutectic. Zinc slag has the influence on rapid degradation of the linings and moreover it also decreases the production quality of ZnO. Analysis results are significant information for minimizing of waste material and easier removing of stuck slag.
Keywords:
zinc slag; production of zinc oxide; analysis of slag; phases
Available at various institutes of the ASCR
Analysis of slag material in the production of zinc oxide
The given paper is closely connected with determination of character and morphology of slag generated in the production of ZnO. Hazardous situations relating to occurrence of these elements are hidden ...
On an estimation of the exponent of the stress singularity: three dimensional problems and effect of residual stresses on a crack arrested on the interface
Máša, Bohuslav; Náhlík, Luboš; Hutař, Pavel
2014 - English
The main aim of this paper is an investigation of the crack behavior in the ceramics laminates. Especially, the problem of the estimation of the stress singularity exponent in such a material using different approaches is closely described. Since analytical approach is a suitable tool for two dimensional problems, introducing residual stresses, which can be result of used procedures during composite production, may influence value of the stress singularity exponent. Unfortunately, there is formally no analytical tool available to introduce residual stresses. Moreover, when the three dimensional geometry is investigated, effects of complicated stress distribution in front of the crack tip are of crucial importance for crack behavior. Hence using numerically obtained stress distribution appears to be the only way, how to capture the effect of residual stresses and three dimensional geometry of the crack front. The stress singularity exponent can be directly determined from stress components in front of the crack tip and/or from displacements at faces of the crack. Both can provide good results and give us a solution, which cannot be obtained analytically. In following text the procedure will be described in more detail and shown results obtained on ceramic laminate.
Keywords:
Stress singularity exponent; Residual stress; Singular stress concentrator; Material interface; Ceramic composites
Available at various institutes of the ASCR
On an estimation of the exponent of the stress singularity: three dimensional problems and effect of residual stresses on a crack arrested on the interface
The main aim of this paper is an investigation of the crack behavior in the ceramics laminates. Especially, the problem of the estimation of the stress singularity exponent in such a material using ...
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