Abstract
The effects of loading rate on deformation and fracture properties of structural steels have been investigated using notched round bar steel specimens. FEM analysis was carried out to evaluate stress and strain condition around notch region. Because of high speed straining, plastic work leads to temperature increase in the vicinity of notch tip. Strain rate dependence of tensile strength was evaluated equally as temperature by strain rate-temperature parameter (R parameter) considering temperature increase in the notch region. It is proved that ductile-brittle transition temperature did not rise with dynamic loading in the case of the steels with good deformability or the specimen with low stress concentration factor. This is because that large amount of plastic deformation leads to high temperature increase around the notch under dynamic loading, which eliminates the effect of strain rate for brittle fracture.
