Fatigue crack growth and closure behavior under random loadings in 7475-T7351 aluminum alloy

Fatigue crack growth and closure behavior under random loadings in 7475-T7351 aluminum alloy is investigated by performing various random loading tests. The effects of random load spectrum, history length, and stress ratio on the crack growth and closure behavior are discussed. The crack opening load was automatically determined by using the normalized-extended ASTM method. The crack opening load is nearly constant during a random loading block and is mainly governed by the largest load cycle in a random load history, irrespective of random load spectrum and history length. The fatigue crack growth under random loading can be well described by the crack closure concept.