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Vliv plasmové nitridace na únavovou životnost vysocepevných ocelí při biaxiálním zatěžování / Influence of Plasma-nitriding on Fatigue Life of High-strength Steels under Biaxial Loading

This work deals with fatigue life and fractographycal analysis of plasma-nitrided and virgin specimen made of the low-alloy high-strength steel. Specimens were subjected to in-phase combined bending-torsion loading. The work is focused on three groups of problems. The first group of problems was associated with the fatigue life and its prediction. The objective was to examine a relationship between the presence of the nitrided layer and fatigue life. The application of surface layers has significantly improved the fatigue life in the high-cycle region. An extended comparison between classical and advanced multiaxial criteria was performed. Criterions proposed by Marin and Matake were found to be most precise. The second objective of this work was to examine a relationship between the loading ratio ( is the bending amplitude and is the torsion amplitude ) and the fracture surface topography in the highcycle fatigue. Properties of fracture surfaces were quantified by many roughness and fractal parameters. Many roughness parameters start to incrise rapidly above a critical value of the loading ratio zc = 0,5. The last part of this work deals with the fractographical analysis of fish-eye cracks that were formed in plasma-nitrided steel specimens under symetrical bending, symetrical torsion and biaxial in-phase bending-torsion combinations.

Identiferoai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:233936
Date January 2010
CreatorsMajor, Štěpán
ContributorsKohout, Jan, Růžička,, Milan, Obrtlík, Karel, Pokluda, Jaroslav
PublisherVysoké učení technické v Brně. Fakulta strojního inženýrství
Source SetsCzech ETDs
LanguageCzech
Detected LanguageEnglish
Typeinfo:eu-repo/semantics/doctoralThesis
Rightsinfo:eu-repo/semantics/restrictedAccess

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