In situ digital image speckle correlation (DISC) observation of plastic strain increment in low-carbon steel

The present work is aimed at studying the macroscopic localization of plastic strain in low-carbon steel AISI A283 Grade C. The evolution of macroscopically localized plastic strain at various stages of strain hardening is visualized via a Digital image speckle correlation (DISC) method. The processing of stress-strain curves of the steel samples enabled one to distinguish the following stages of strain hardening: the yield point, the parabolic hardening, and the pre-failure. The inspection of local strain distributions reveals that the parabolic work hardening is presented by a system of stationary plastic strain centers placed at equal distances. To perform a comprehensive analysis of local elongations from the parabolic work hardening toward the pre-failure stage, the total elongation components were measured at the strain centers. The average total elongation is found to be almost constant at the parabolic work hardening, but abruptly increases when approaching the pre-failure stage. The plastic strain instability is highlighted, as well, by the rising total elongation (amplitude) at the strain sites