Acoustic emission during monotonic and cyclic fracture toughness tests of 304LN weldments

Determination of initiation fracture toughness of ductile materials is a challenging task due to the ambiguity associated with the identification of the point of departure of the initial linear region of the fracture resistance curve. Acoustic emission (AE) is a technique that is capable of directly indicating the crack initiation point during fracture toughness tests using a single specimen. The objective of this investigation is to illustrate some results related to monotonic and cyclic fracture behaviour of AISI 304LN weldments estimated by this ‘combined type’ experiment. The use of cyclic J-integral tests has been proposed to simulate the deleterious effect of periodic load reversals during monotonic loading. A comparative analysis of all these data leads to the conclusion that the fracture toughness of a material determined from AE parameters is generally conservative compared to that obtained by conventional techniques.