Towards Predicting Necking Instability in Metals by Acoustic Emission Model Analysis

Abstract

We have enhanced a basic single-variable dislocation evolution modelling framework to encompass the acoustic emission (AE) characteristics observed in metals and alloys during the homogeneous strain hardening stage up to the point of macroscopic necking instability under tensile stress. To validate our proposed modelling approach, we conducted comprehensive experiments using pure Ag, Cu, Al, and Ni, representing fcc metals with stacking fault energies increasing in the listed order of materials. Our model successfully captures both previously established and newly discovered patterns in the evolution of the AE spectral density. A key focus of this research is to demonstrate the ability to directly derive the critical parameter that governs the evolution of dislocations and, consequently, overall strain hardening, namely the rate of dynamic dislocation recovery, directly from AE measurements. As a prime result, we can predict the conditions leading to necking, specifically the necking strain, well in advance solely from AE data.