Effect of Defect on the Dynamic Strain Aging Behavior of Low Carbon Ferritic Steels

Gr.C, and A333 Gr.6, are commonly used as piping material in nuclear power plants (NPPs). These ferritic steels are known to exhibit dynamic strain aging (DSA) when exposed to a certain range of elevated temperatures, including operating temperatures of NPPs, during tensile deformation. DSA in low carbon steels is related to the interactions between free carbon and nitrogen atoms and dislocations during plastic deformation, and it leads to abnormal increase in strength and decrease in ductility and fracture toughness. Also, the DSA behavior is sensitive to the deformation rate. Therefore, DSA phenomenon has been considered to be a cause of uncertainty in the integrity evaluation of carbon steel components in NPPs, and a number of studies have been investigated the behavior of DSA under uni-axial tensile deformation. However, the DSA behavior under notched and defective conditions has not been investigated extensively, although in real components the plastic deformation and damage occur at stress concentrated area, such as notch and defects. The objective of the present study is to investigate the effect of defect on the DSA behavior of low carbon ferritic steels. For this objective this study conducted a series of tensile tests using notched-bar specimens as well as standard tensile specimens. DSA behavior in notched-bar specimens was investigated and the effect of structural defect on the DSA behavior was discussed