APPLICATION OF THE STRIP-YIELD CRACK CLOSURE MODEL TO CRACK GROWTH PREDICTIONS FOR STRUCTURAL STEEL

摘要

Though the strip yield (SY) type models for crack growth predictions are currently a widely used tool to simulate fatigue crack growth in aircraft materials, their adequacy for structural steel remains unknown. In this paper, the SY model ability to simulate crack growth observed in fatigue tests on a structural steel is explored. It is shown first that the predictions from the SY model included in the NASGRO software do not reproduce the effects of the stress ratio and the applied stress level observed under constant amplitude loading. Also, they do not correctly account for crack growth retardation after a single overload cycle. Next, a SY model developed by the present authors, which incorporates three independent constraint factors on yielding at the crack tip, is applied. The model calibration for the structural steel is implemented through choosing the constraint factors to match the experimentally observed and predicted by the model the cyclic stress-strain behaviour at the crack tip. The proposed calibration concept enables the model predictions to quantitatively cover all trends in crack growth observed in the present tests.