An investigation into the phenomenon of macroscopic plastic deformation localization in metals

Experimental and theoretical studies are combined to investigate the phenomenon of macroscopic plastic deformation localization in metallic tensile specimens of AL6061, HSLA350 and Q235. The longitudinal strain and cross-section reduction of the specimens at different instant during testing are estimated through the measurement technique of three dimensional digital image correlation (3D-DIC). The Ling weighted-average method referred as WAM is used to compare the true stress-strain relation obtained from the experiment. A new mathematical model is suggested to estimate the localization zone length, which is a crucial parameter that can be used to anticipate the behaviour of metals past the peak load. The effect of material property on the necking zone length is examined. The experimental results show that the axial strain within the necking zone is non-uniform. It is also found that the WAM can precisely derive the true stress of steels Q235 and HSLA350 but not AL6061. The localization zone length of the round specimens Q235, HSLA350, and AL6061 equals six, five, and four times their initial diameter, respectively. Materials with a higher fracture strain ratio to the ultimate strain have a shorter necking zone length. This work provides insights into the physical mechanism of macroscopic plastic deformation localization.