a The German Aerospace Research Establishment, Institute for Materials Research, Postfach 90 60 58, 5000, Köln 90, Federal Republic of Germany
Abstract:
The fatigue threshold, ΔKth, is strongly influenced by the stress-ratio, ie by the loading conditions. Results for a Ti6A14V alloy show that a ΔK exists for non-propagating fatigue cracks which is independent of loading conditions. This ΔK is called the fatigue tolerance range and is denoted by ΔKK. The fatigue tolerance range corresponds to that part of the ΔKth during which the fatigue crack is open. Arguments that the fatigue tolerance range has to be explicitly incorporated in equations predicting fatigue crack growth rates are presented.