The Effect of Load Interaction and Sequence on the Fatigue Behavior of Notched Coupons

CONSTANT AMPLITUDE FATIGUE TESTS WITH VARIOUS CONDITIONS OF OVERLOADS WERE CONDUCTED TO UNDERSTAND THE EFFECTS OF LOAD INTERACTION AND SEQUENCE IN NOTCHED COUPONS. THE RESULTS WERE ANALYZED WITH PARTICULAR EMPHASIS ON THE LOCAL RESIDUAL STRESSES AT NOTCHES. FATIGUE LIFE RESULTS FROM THE TESTS HAVING A VARIATION IN THE NUMBER OF CYCLES BETWEEN THE PERIODIC OVERLOADS WHICH REINFORCE THE CONCEPT OF A FADING RESIDUAL STRESS. OTHER FATIGUE LIFE TRENDS COULD BE PREDICTED BY ASSUMING A STABLE RESIDUAL STRESS. CONDITIONS WHICH COULD CAUSE CYCLE-DEPENDENT OVERLOAD RESIDUAL STRESSES ARE DISCUSSED. AN EXPONENTIAL ANALYSIS FORM IS SUGGESTED FOR CALCULATING THE CYCLE-DEPENDENT LOCAL STRESSES FOR APPLICATION TO CUMULATIVE DAMAGE PREDICTIONS. /ASTM/