Evolution of local deformation field inside adiabatic shear band of 1018 steel studied using digital image correlation with micro-speckles

Adiabatic shear band (ASB) is widely observed in metals and alloys under impact loading as a significant failure mechanism. Exhibiting severe localization over a short period of time, ASB imposes great challenges in characterizing the evolution of the local deformation field. Most existing theoretical models employed the assumption of laminar-flow-like shear deformation inside the band, while non-uniform “hot spots” have also been observed along a propagating shear band. In this study, the evolution of the local deformation field inside the ASB was investigated based on the digital image correlation (DIC) technique with micro-speckles. Destructive micro-speckles were created using laser etching within the shearing region to resolve localized deformation. Based on experimental results of 1018 steel specimen under impact loading, ASB evolution along the shearing plane was divided into two distinct stages: in the first stage, the deformation localized almost uniformly along the band, which is consistent with the laminar flow assumption; whereas in the second stage, the deformation was highly non-uniform and exhibited distributed strain-localizations, which could be closely associated with hot-spot formation and should be taken into account especially during the post-localization stage. Our study revealed the existence of “hot spots” based on a direct measurement of the deformation field, and shed more light on the understanding of the entire evolution process of ASB formation.