Experimentelle und rechnerische Untersuchungen des Rissschließens in Standardproben

The paper presents an experimental study of fatigue crack closure behaviour in standard specimens of types C(T), SE(T) and M(T) made of the steel 25CrMo4. During fatigue crack growth (FCG) tests performed within the Paris regime, at R = 0.1, crack closure and crack opening are monitored using stain gauges mounted both at specimen's back face and along the crack propagation line. The test results reveal different FCG rates for different specimens at the same level of the stress intensity factor range, DK. This behaviour corresponds to some extent with the evaluation of crack closure, while the correlation dependency is assumed to be more complex than achieved from the conventional crack closure concept. The experimental findings turn out to qualitatively agree with results of numerical modelling of plasticity induced crack closure.