Effect of periodic overloads on the ∆K threshold estimates in an aluminum alloy

Abstract

The effect of single overloads on the assessment of the threshold range of stress intensity factor in aluminum alloy AA7085 is analyzed. It is shown that in the cases where the testing procedure for measuring the ∆K threshold includes periodic overloads, the real threshold value might be underestimated by up to 49%. The estimates obtained in this study using a standard procedure are equal to ∆Kth=1.14 MPa √m, while the real value is 0.71 MPa √m. It is argued that a possible error in measuring ∆K threshold is to be compensated in fatigue tests by varying the load amplitude.