The use of acoustic emission to evaluate critical values of K and J in 7075-T651 aluminum alloy

The acoustic emission behavior during fracture toughness tests on 7075-T651 aluminum alloy was studied. Critical values of K and J determined by acoustic emission were approx. 6 and 10% lower than values of KIC and JIC respectively, which demonstrates the sensitivity of acoustic emission to detect the start of crack propagation in this alloy. The principal source of acoustic emission, as indicated from metallographic and fractographic observations was the fracture of inclusion-type particles. Under the experimental conditions employed, crack propagation occurred in a series of crack bursts or pop-ins. The load-displacement curves thus obtained well-suited for evaluating J as a function of crack growth.