Micro defects formation and dynamic response analysis of steel plate of quasi-cracking area subjected to explosive load

Abstract

As the protective component, steel plate had attracted extensive attention because of frequently threats of explosive loads. In this paper, the evolution of microstructure and the mechanism of damage in the quasi-cracking area of steel plate subjected to explosive load were discussed and the relationships between micro defects and dynamic mechanical response were revealed. After the explosion experiment, five observation points were selected equidistant from the quasi-cracking area of the section of the steel plate along the thickness direction, and the characteristics of micro defects at the observation points were analyzed by optical microscope (OM), scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD). The observation result shows that many slip bands (SBs) appeared, and the grain orientation changed obviously in the steel plate, the two were the main damage types of micro defects. In addition, cracks, peeling pits, grooves and other lager micro defects were appeared in the lower area of the plate. The stress parameters of the observation points were obtained through an effective numerical model. The mechanism of damage generation and crack propagation in the quasi-cracking area were clarified by comparing the specific impulse of each observation point with the corresponding micro defects. The result shows that the generation and expansion of micro defects are related to the stress area (i.e. the upper compression area, the neutral plane area, and the lower tension area). The micro defects gather and expand at the grain boundary, and will become macroscopic damage under the continuous action of tensile stress. Besides, the micro defects at the midpoint of the section of the steel plate in the direction away from the explosion center (i.e. the horizontal direction) were also studied. It was found that the specific impulse at these positions were much smaller than that in the thickness direction, the micro defects were only SBs and a few micro cracks, and the those decreased with the increase of the distance from the explosion center.