Abstract
The growth and closure behavior of a small crack initiated at a notch root was investigated for SUS 304 and SM41A steels under the situation of enhanced notch plasticity. An acceleration of growth rate as well as an increase in crack-opening range were observed for a small crack which was embedded in the notch-plastic zone. All of the growth data for the small crack at the notch root were successfully correlated with those for long cracks by the effective stress intensity factor range, ΔKeff. ΔKeff was found to be a controlling parameter for crack growth up to higher nominal stress range, as far as the crack closure was observed and the notch-root plastic region was surrounded by the elastic region. A primary controlling factor for the closure of the small crack at the notch root was found to be notch-root plasticity. This was supported by the analytical study by using the finite element method.
