Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 58: Topical Session: Fundamentals of Fracture - Fatigue Fracture
MM 58.2: Talk
Thursday, March 14, 2013, 16:15–16:30, H4
Propagation Behaviour of Microstructurally Short Fatigue Cracks in the High Cycle and Very High Cycle Fatigue Regime — •Hans-Jürgen Christ1 and Claus-Peter Fritzen2 — 1Institut für Werkstofftechnik, Universität Siegen, Germany — 2Institut für Mechanik und Regelungstechnik - Mechatronik, Universität Siegen, Germany
It is generally accepted that crack initiation mechanisms and short fatigue crack propagation processes govern fatigue life in the high and very high cycle fatigue regimes. Local slip irreversibility causes crack initiation far below the fatigue limit. However, interaction of the crack tip with microstructural barriers, such as grain boundaries or second phases, leads to a decrease and eventually to a stop in the crack-propagation rate. If this is the case even for the weakest site the fatigue limit is reached. In the present contribution examples for propagating and non-propagating conditions of short fatigue cracks are given for a single-phase beta-titanium alloy, a duplex steel, a metastable austenitic stainless steel and the titanium alloy Ti6Al4V. A numerical model based on the boundary-element method has been developed, where crack propagation is described by means of partially irreversible dislocation glide on crystallographic slip planes in a polycrystalline model microstructure. This concept is capable to account for the strong scatter in fatigue life for very small strain amplitudes and to contribute to the concept of tailored microstructures for improved cyclic-loading behaviour.