Jaroslav Polák
Academy of Sciences of the Czech Republic
Transmission electron microscopyLüders bandDislocationComposite materialAmplitudeHardening (metallurgy)MetallurgyMaterials scienceSuperalloyScanning electron microscopeAustenitic stainless steelSofteningFatigue testingSurface reliefSlip (materials science)Cyclic stressStructural engineeringCrack closurePlasticityEffective stressAustenite
Publications 284
#1Milan Heczko (OSU: Ohio State University)H-Index: 10
#2Veronika Mazánová (OSU: Ohio State University)H-Index: 8
Last. Michael J. Mills (OSU: Ohio State University)H-Index: 75
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Abstract Cylindrical specimens of CrCoNi alloy with electropolished surfaces were subjected to constant total strain amplitude low cycle fatigue. The alloy exhibited an initial period of cyclic hardening followed by cyclic softening until failure occurred. At the end of hardening stage at the peak of cyclic stress, well-developed persistent slip markings (PSMs) consisting of extrusions and intrusions were associated with thin deformation twins. A sophisticated experimental workflow was designed ...
#1Stanislava Fintová (CAS: Academy of Sciences of the Czech Republic)H-Index: 12
#2Ivo Kuběna (CAS: Academy of Sciences of the Czech Republic)H-Index: 14
Last. Jaroslav Polák (CAS: Academy of Sciences of the Czech Republic)H-Index: 39
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Abstract Pure polycrystalline copper has been subjected to cyclic loading with frequencies from 4 Hz to 20 kHz. With increasing frequency, the S-N curve was shifted to a higher number of cycles to fracture. Quasi-static and dynamic tensile tests were performed to identify the strain rate sensitivity corresponding to the increase of the cyclic frequency in order to explain the shift of the S-N curve with the frequency. Surface relief evolution has been studied in specimens cycled with various str...
Abstract null null Surface relief evolution and fatigue crack initiation of Rene 41 superalloy was studied. The material was tested in two thermodynamical states: solutionised and aged. Cylindrical specimens were cycled at total strain amplitude 0.8% at room temperature. In order to study relevant mechanisms resulting in surface relief formation and eventually fatigue crack initiation, cycling was interrupted at definite number of elapsed cycles. After each interruption, the specimen surface was...
#2Ivo KuběnaH-Index: 14
Last. Miroslav ŠmídH-Index: 11
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Superaustenitic steel Sanicro 25 has been subjected to in-phase and out-of-phase thermomechanical fatigue cycles in the temperature range from 250°C to 700°C. Both constant strain rate cycling and cycling with 10 minutes dwell at peak temperature were applied. The effect of the dwells on the cyclic response, internal structure and damage mechanism was studied. Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were evaluated. The transmission electron microsco...
#1Boris KrškaH-Index: 14
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Abstract Interactions of mobile dislocations in persistent slip bands with ladder-like structure are analyzed and production rates of point defects, preferably vacancies, are derived. Previous resistivity measurements in copper single crystals and polycrystals are used to derive the growth of vacancy concentration during cyclic loading at low temperatures. The parameters of the growth law are derived from the initial growth rate and saturated vacancy concentration. The consequences of vacancy pr...
1 CitationsSource
Abstract The cyclic plastic response and damage evolution in isothermal high temperature constant strain rate cycling and during in-phase thermomechanical fatigue in superaustenitic Sanicro 25 steel have been studied both with and without introduction of dwells at maximum strain. Fatigue hardening/softening curves and fatigue life curves are reported for all types of fatigue tests. Rapid hardening and a tendency to saturation has been found primarily in isothermal cycling with dwells and in ther...
1 CitationsSource
#2Milan HeczkoH-Index: 10
Last. Michael J. MillsH-Index: 75
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#2Jaroslav PolákH-Index: 39
Last. Radek MelichH-Index: 9
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