Optical observations and numerical simulations on the evolution of ASB in structural steel

Abstract
Many failures of metals under impact loadings result from the occurrence and evolution of Adiabatic Shear Band (ASB) and it becomes a key issue in the research of damage mechanisms. The theoretical study in this field is mainly focused on the relationship among the mechanical properties, thermal physical parameters and the loading condition of the specimen in one dimensional frame to determine the possibility of the ASB occurrence. By experimental investigations, the features of ASB of titanium alloy, tungsten alloy and high-strength structural steel, including deformation fields, local temperature and the threshold value for ASB generating, can be detected. However, since there is little research work on the real-time and in-situ measurements on the evolution of ASB, the failure details according to the shear-localization is still unknown. In this paper, the real-time observations and visualizations on the evaluation of ASB in 45 steel in different impact conditions on SHPB are presented. The generating and evaluating processes in a single sample are detected and analyzed by an optical system and the self-designed software based on Digital Correlation method with high resolution. At the same time, the numerical simulations in LS-DYNA simulator and micro-observations by SEM are achieved and the results agree quite well with the experimental ones.