THE INFLUENCE OF VARIABLE AMPLITUDE LOADING ON CRACK CLOSURE AND NOTCH FATIGUE BEHAVIOR

Smooth and notched 1045 steel specimens were tested under constant amp litude, R = -1 loading and under a variable amplitude load history con sisting of periodic overloads followed by high R-ratio small cycles. T he notched specimens exhibited a notch size effect under constant ampl itude loading, but the effect was reduced in the long life region (def ined as a fatigue life > 10(7) cycles) under the variable amplitude lo ad history. A crack growth model that followed crack closure changes o n a cycle-by-cycle basis adequately predicted fatigue life for the per iodically overloaded notched specimens. (C) 1997 Elsevier Science Ltd.