Influence of grain size on frequency spectra of AE signal generated during tensile deformation in an AISI type 316 stainless steel

Abstract

Frequency analysis of acoustic emission (AE) signals has been applied to find out the influence of grain size on acoustic emission generated during the tensile testing in an AISI type 316 stainless steel and the results obtained are discussed. It is known that the influence of grain size on AE during tensile testing is complex. The main factors influencing AE signal in austenitic steels during tensile deformation at room temperature from specimens of different grain sizes are (i) glide distance of moving dislocations, (ii) grain boundary sources, (iii) dislocation structure, (iv) velocity of dislocations & (v) characteristic frequencies of acoustic emission. Hence, use of resonant sensors and time domain parameters will not help in explaining the influence of grain size on AE behavior. This has already been reported, based on the studies made at the authors' laboratory in the case of an AISI type 316 stainless steel. It has been suggested by rouby et al. That use of broadband sensor along with frequency analysis approach should be applied to explain the AE signal variations with changes in grain size. The influence of progressive plastic deformation (strain) in an AISI type 316 stainless steel, having 50 micrometers average grain size, on the frequency of AE generated has been recently communicated from the authors' laboratory. This study indicated that the frequency of emission increases with increase in strain. The increase in frequency was postulated to correspond to the increased waiting time for mobile dislocations at short range obstacles. In this work, the influence of grain size on AE in the same material for various plastic deformations has been studied by frequency domain analysis approach and the results are discussed in this paper.