The influence of notch on the acoustic emission generated during tensile testing of nuclear grade AISI type 304 stainless steel

Acoustic emission (AE) generated during tensile deformation of a nuclear gr ade AISI type 304 stainless steel with the presence of notches has been stu died. Comparative analysis of AE activity from unnotched and notched specim ens with varying notch lengths, as opposed to similar results reported in t he literature for beryllium and aluminium alloys, has been made. It can be inferred from the present results that: (a) prior to and during yielding, h igher acoustic activity is observed in notched specimens unlike those repor ted for beryllium and aluminium alloys and also the total AE counts increas e with increase in the initial notch length, and (b) beyond yielding, acous tic activity of both the notched and unnotched specimens reduces. These obs ervations have been explained by considering the increased localised deform ation at the notch tip prior to and during yielding and by taking into acco unt the phenomenon of blunting at the notch tip beyond yielding. An analysi s of the total AE counts (N) with respect to the stress intensity factor (K ) operative at the notch tip during macroyielding shows N to bear a relatio nship to K as N = AK(m) when A and m are constants. The value of nz is foun d to lie between 1.11 and 1.93 unlike the reported value of m greater than or equal to 4 for aluminium alloys. The observed acoustic emission activity just before and during tearing of the notched specimens is also noted to b e higher than that observed during necking elongation of unnotched specimen s. (C) 2000 Elsevier Science S.A. All rights reserved.