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NANOSTRUCTURE CHARACTERIZATION OF IN738LC SUPERALLOY FATIGUED AT HIGH TEMPERATURE
Petrenec, M. ; Strunz, Pavel ; Gasser, U. ; Heczko, Milan ; Zálešák, J. ; Polák, Jaroslav
The nanostructure of Inconel 738LC Ni-superalloy strengthened by trimodal Y precipitates distribution was investigated after Low Cycle Fatigue (LFC) loading at temperature 700°C. Different microscopic techniques as Scanning Electron Microscope (SEM) equipped with STEM detectro, transmission Kikuchi diffraction in the SEM, transmission electron microscope (TEM) in the bright field mode and high resolution transmission electron mciroscopes (HRTEM) in STEM mode were used for the characterization and quantification of superalloy nanostructure. The characteristic morphology of y precipitates was examined by ex-situ and in-situ Small Angle Neutron Scattering (SANS) at high temperatures. All adopted microscopic techniques indicate that the morphology of y precipitates distributed in the y matrix as recived state corresponds to two types, i.e. large cuboid-like precipitates with the size around 670 nm, and the spherical precipitates with the diameter 52nm. After eh LCF tests at temperature 700°C, the ex-situ SANS measurement yielded addititonal scattering intensities coming from another small y precipitetes with estimated size up to 10nm.
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NANOSTRUCTURE CHARACTERIZATION OF IN738LC SUPERALLOY FATIGUED AT HIGH TEMPERATURE
Petrenec, M. ; Strunz, Pavel ; Gasser, U. ; Heczko, Milan ; Zálešák, J. ; Polák, Jaroslav
The nanostructure of Inconel 738LC Ni-superalloy strengthened by trimodal γ’ precipitates distribution was investigated after Low Cycle Fatigue (LCF) loading at temperature 700°C. Different microscopic techniques as Scanning Electron Microscope (SEM) equipped with STEM detector, transmission Kikuchi diffraction in the SEM, transmission electron microscope (TEM) in the bright field mode and high resolution transmission electron microscopes in STEM mode were used for the characterization of nanostructure. The characteristic morphology of γ’ precipitates was examined by ex-situ and in-situ Small Angle Neutron Scattering (SANS) at high temperatures. All microscopic techniques indicate that the morphology of γ’ precipitates distributed in the γ matrix as received state corresponds to two types, i.e. large cuboid-like precipitates with the size around 670 nm, and the spherical precipitates with the diameter 52 nm. After the LCF tests at temperature 700°C, the ex-situ SANS measurement yielded additional scattering intensities coming from another small γ’ precipitates with estimated size up to 10 nm.
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Microstructural Investigation and Mechanical Testing of an Ultrafine-grained Austenitic Stainless Steel
Chlupová, Alice ; Man, Jiří ; Polák, Jaroslav ; Karjalainen, L. P.
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.
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Využití manipulačních zařízení ve skladovém hospodářství vybraného obchodního řetězce.
POLÁK, Jaroslav
Bakalářská práce byla zpracována v rámci řádného ukončení Bakalářského studia Dopravní a manipulační technika na Zemědělské fakultě Jihočeské univerzity v Českých Budějovicích.. Bakalářská práce se zaměřuje na dopravní a manipulační techniku, která lze použít, nebo je používána v obchodní síti Bauhaus. V zhledem k propojení manipulační techniky s technikou skladování je v této práci také obsažena problematika skladování a paletizace. Práce seznamuje čtenáře s různými druhy manipulační techniky, možnostmi manipulace, skladováním materiálu a s prostředky které jsou potřebné k této činnosti. Nikoli však s v nitřní funkcí, technickým řešením dané manipulační techniky. Popisuje možnosti efektivního využití místa pro skladování materiálu, případně doporučuje dané řešení V jednotlivých kapitolách této práce je popisována daná problematika a na obrázcích jsou uvedeny příklady řešení. V závěru práce jsou porovnány vytčené cíle projektu s dosaženými výsledky. Nechybí doporučení jak na tuto práci dále navázat a dále ji rozvíjet.
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Proceedings of the 16th International colloquium Mechanical Fatigue of Materials
Polák, Jaroslav ; Kruml, Tomáš ; Man, Jiří
The XVI International Colloquium on Mechanical Fatigue of Metals was organized by the Institute of Physics of Materials, Academy of Sciences of the Czech Republic in Brno, in September 24-26, 2012. The Colloquium has been opened to participants from all countries interested in the subject of fatigue of metallic materials. The proceedings contains 39 abstracts of 35 oral and of 4 poster contributions by 122 authors from 18 countries to be presented during the Colloquium.
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Analysis of cyclic plasticity of fatigued nickel based superalloys at elevated temperatures
Petrenec, Martin ; Tobiáš, Jiří ; Polák, Jaroslav ; Šmíd, Miroslav ; Chlupová, Alice ; Petráš, Roman
Cyclic strain controlled multiple step tests have been performed on cylindrical specimens of cast Inconel 738LC superalloy at 23 and 800 °C and Inconel 792-5A superalloy at 800 °C in laboratory atmosphere. The effect of temperature on the cyclic stress-strain response characterized by internal and effective cyclic stress components and on the dislocation arrangement has been studied. The evolution of the effective and internal stress components and effective elastic moduli were derived from the hysteresis loops analyzed according to the statistical theory of the hysteresis loop. Cyclic hardening/softening curves and shortened cyclic stress-strain curves were obtained at all temperatures in both superalloys. The shortened cyclic stress-strain curves (CSSCs) can be fitted by power law at all temperatures and for both materials. They are shifted to lower stresses with increasing temperature. The CSSC of Inconel 792-5A is shifted to higher stress amplitude in comparison with that of Inconel 738LC due to different number and type of precipitates. Observation of dislocation structures by TEM revealed cyclic strain localization into persistent slip bands. Cyclic stress-strain response is compared at all temperatures in both superalloys and discussed in relation to the changes of internal and effective stress components and microstructural parameters of the material. Higher stress response of the Inconel 792-5A than of the Inconel 738LC superalloy at 800°C is due to higher effective stresses of respective γ´ phases.
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Fatigue crack initiation — the role of point defects
Polák, Jaroslav ; Man, Jiří
The role of point defects in the formation of surface relief and in the initiation of a fatigue crack in crystalline materials is analyzed. The dislocation interactions in the bands of intensive cyclic slip are specified and relations describing the formation and annihilation of interstitial and vacancy type defects are derived. The formation, annihilation and migration of point defects is proposed to be responsible for the mass redistribution within PSB and between PSB and the matrix boundary. The redistribution of the matter results in local tensile and compressive stresses that are relaxed by continuous dislocation movement within PSB and lead to the formation of characteristic surface relief in the form of extrusions and intrusions.
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Low Cycle Fatigue and Analysis of the Cyclic Stress-strain Response in Superalloy Inconel 738LC
Tobiáš, Jiří ; Chlupová, Alice ; Petrenec, Martin ; Polák, Jaroslav
The paper describes the results of fatigue behavior study on cast polycrystalline nickel based superalloy tested at 23 and 800 °C. Cylindrical specimens of Inconel 738LC were cyclically strained under total strain control to fracture and multiple step tests were performed to study the effect of temperature on the internal and effective cyclic stress components. Fatigue life curves were approximated by the Manson- Coffin and Basquin laws. The resulting curves were shifted to lower fatigue lives with increasing temperature. The evolution of the effective and internal stress components and effective elastic modules were derived from the hysteresis loops which were analyzed according to the statistical theory of hysteresis loop. Cyclic stress-strain response at both temperatures and the changes of internal and effective stress components were discussed in relation to microstructural parameters of the superalloy.
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Metodika hodnocení rezistence transgenní švestky, Prunus domestica L., klon C5 k viru šarky švestky a ke směsným infekcím s dalšími viry: uplatněná certifikovaná metodika
Polák, Jaroslav ; Kumar, Jiban ; Jarošová, Jana
Metodika obsahuje metodický postup založení polního pokusného sadu švestky s transgenní rezistencí k viru šarky švestky (PPV), a vyhodnocení rezistence P. domestica, klon C5 k infekci PPV a kombinacím s dalšími dvěma viry, ACLSV a PDV, způsobujícími pseudošarku.Pomocí ELISA, ISEM, RT-PCR a hodnocením příznaků byla prokázána rezistence P. domestica L., klon C5 s genem kapsidu PPV vůči PPV-Rec a směsným infekcím s dalšími dvěma viry.
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