Modeling crack closure and damage in variable amplitude fatigue using smooth specimen fatigue test data

► In constant amplitude fatigue loading the crack opening stress increases in an exponential manner until it reaches a steady state level. The steady state crack opening stress levels follow the trends predicted by model proposed. ► Deriving the steady state crack opening stresses from constant amplitude and underload fatigue data for smooth specimens gave a good fit to the crack opening stresses measured using crack growth specimens. ► Using the test procedure suggested in this paper, we were able to obtain data for crack opening stress recovery to a steady state level after underloads (and the associated crack closure parameter) from smooth specimen tests. ► The effective intensity versus crack growth rate curve parameters obtained from smooth specimen tests give a good fit to the experimental crack growth data.