Study of spatial-time inhomogeneity of serrated plastic flow Al-Mg alloy: Using DIC-technique

Abstract

The aim of the present paper is the investigation of temporal instabilities and spatial localization due to the Lüders behavior, the Portevin-Le Chatelier effect and the shoulder or necking effect during uniaxial tension tests of aluminum-magnesium alloy. This paper presents the brief description of the test procedure and experimental results of carrying out research by the combined use of a servo-hydraulic biaxial test system Instron 8850 and a non-contact 3-D digital image correlation measurement system Vic-3D. The digital image correlation is a highly effective computer-vision-based technique, which provides estimation of the displacement and strain fields on specimen surface by matching the reference subsets in the undeformed image (before loading) with the target subsets in the deformed images (captured during test). The evolution of inhomogeneous axial strain and axial strain rate fields has been illustrated for each stage of material's deformation. To estimate the kinematics of serrated or jerky flow due to the strain bands propagation, the strain versus time curves and strain diagrams are given here. The experimental results show the recurrence in the strain distribution leveling along the specimen gauge. The changing between the macroscopic localization of the plastic flow, namely the running of the Lüders and PLC bands and the recovery of strain field homogeneity, has been observed.