Quantitative damage evaluation of LY225 steel under monotonic tensile loading based on acoustic emission entropy

Abstract

The purpose of this paper is to establish a quantitative relationship between acoustic emission (AE) signal acquisition data and the void growth model (VGM) of low yield point steel LY225 under monotonic tensile loading, to realize the real-time evaluation of plastic damage and the prediction of ductile fracture of materials. A series of material tests, finite element analysis and scanning electron microscope (SEM) tests were carried out to calibrate the VGM fracture parameters of LY225 steel, including the characteristic length l∗ and the critical value of VGI. It is found that the AE signals under monotonic tensile loading have a prominent two-stage characteristic and the cumulative AE entropy of AE signals in LY225 steel is proportional to the volume of material involved with plastic deformation. Then a bilinear function model between cumulative AE entropy and void growth index VGI is proposed and calibrated with monotonic tensile test results from a set of standard rectangular section specimens, and the effectiveness of the proposed model in more complex stress and strain state is verified by tests of a set of variable cross-section flat specimens.