Characterization of the Crack Toughness Behavior of Structural Steels by the Tearing Modulus Parameter and Acoustic Emission

Abstract

The combination of elastic-plastic fracture mechanics and acoustic emission techniques is used for evaluating the fracture toughness behavior of structural steels. The results show that for certain situations the acoustic emission technique can be used to accurately estimate the J integral at a growing crack and therefore provide predictive information regarding failure in laboratory specimens of different geometries and sizes. The invariance of the normalized J resistance curve is demonstrated for the compact and bend configurations. A simple and realistic test method is proposed for the evaluation of a critical value of the J integral and the tearing modulus parameter in cases in which the scatter is of particular concern. Correlation between acoustic emission and the tearing modulus parameter is presented that permits an acoustic “rating” of the material. In addition, the significance of an extending ductile tear on the structural integrity in terms of tearing modulus and acoustic emission is discussed.