Acoustic emission and fracture of ductile materials

Acoustic emission, radius of the contraction zone on the side of the specimen and load-load point displacement were measured during fracture of single edge notched specimens containing fatigue cracks of different lengths. It was found that there exists a three-fold correlation between formation of a contraction zone, noticeable acoustic emission and deviation from linearity on the load-load point displacement curves. The stress intensity factor K was evaluated from the extent of contraction on the specimen surface and related to the acoustic emission total count. A correction for K was made to account for the considerable plasticity at the crack tip. Finally, a model for the formation and development of the plastic and contraction zones is formulated.