FATIGUE OF V-NOTCHED MEMBERS - SHORT CRACK BEHAVIOR AND ENDURANCE LIMIT

A previous experimental investigation showed that the short crack behavior in severe V-notched geometries is essentially characterized by an initial transient variation of the crack opening level within the notch plastic zone. This result is exploited to derive a general formulation of the endurance limit of V-notched members. Analytical solutions for the stress intensity factor and the notch plastic zone extent are obtained to compute the effective crack driving force DELTA K//e//f//f as a function of notch geometry, crack length and nominal stress. Then, the endurance limit is determined as the nominal stress below which an initiated crack becomes non-propagating, i. e. by equating the minimum DELTA K//e//f//f value at the end of the plastic zone to a threshold value. The endurance limit can be computed only from the V-notch 'stress intensity factor' and the material threshold and cyclic yield stress.