Národní úložiště šedé literatury Nalezeno 1 záznamů.  Hledání trvalo 0.01 vteřin. 
Early Stages of Fatigue Damage of Steels for Fusion Energetics
Kuběna, Ivo ; Spätig, Philippe (oponent) ; Lukáš, Petr (oponent) ; Kruml, Tomáš (vedoucí práce)
The main aim of the thesis is to explain fatigue behaviour of the ODS Eurofer steel, 14Cr ODS ferritic steel produced in the CEA (Commissariat a l’énergie atomique, Saclay, France) and 14Cr ODS ferritic steel produced in the EPFL (École Polytechnique Fédérale de Laussane, Switzerland). The results are compared with non–ODS variant of Eurofer steel, if possible. This work is part of a wide collaboration coordinated by the EFDA (European Fusion Development Agreement) on development of structural materials for future fusion reactors. The following experiments were carried out: • Standard fatigue experiments were performed at room temperature, at 650 and at 750 . Cyclic hardening/softening curves, cyclic deformation stress–strain curves, Coffin–Manson curves and Wöhler curves were measured. Detailed analysis of hysteresis loops was performed. • The microstructure of the as–received state was studied by TEM and compared with the microstructure after fatigue loading in order to reveal microstructural changes due to fatigue loading. • Surface roughening due to cyclic plastic localisation was observed. Crack initiation sites were detected and the mechanism of crack initiation was analysed. • Kinetics of small fatigue crack growth was measured. It was found that fine oxide dispersion strengthens studied materials significantly, reduces cyclic softening and stabilises the microstructure in the whole range of testing temperatures. The maximum application temperature is increased. Significant differences in fatigue life of the ODS steels were found and explained by differences in crack initiation mechanisms and small fatigue crack growth rate.

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