Experimental results on fatigue crack closure for two aluminum alloys

Abstract Fatigue crack closure measurements were performed on two aluminum commercial alloys with different yield strength levels. The opening loads were determined on the basis of the non-linear reversible correlation between the applied load and the crack opening displacement. An experimental procedure which amplifies such a non-linear behavior was used. The experimental data indicate that a strong correlation between the opening stress intensity factor, K op , and the maximum value of the stress intensity factor during the fatigue cycle, K MAX , exists. Such a correlation would not depend on the load ratio, R , and it suggests to consider a “master” curve which represents the effective stress intensity range, ΔK EFF , as a function of K MAX for a given material. This curve allows to rationalize several basic features of the fatigue crack growth behavior.