NOTCH FATIGUE BEHAVIOR AS INFLUENCED BY PERIODIC OVERLOADS

The fatigue behaviour of centre-notched specimens of a 2024-T351 alumi nium alloy is examined under a variable-amplitude loading sequence con sisting of a periodic compression-tension overload of yield magnitude followed by smaller high stress ratio cycles. It is found that the eff ects of both overloads and notches can act simultaneously to reduce se verely the fatigue strength of notched specimens and that the notch-si ze effect that is typically observed under constant-amplitude loading is reduced by periodic overloading. This is attributed to the absence of crack closure in the loading sequence examined. A crack growth mode l is developed to predict the fatigue life of notched specimens subjec ted to periodic overloads.