Investigation of dynamic strain aging in SA106 Gr.C piping steel

Tensile and J-R tests were carried out under various temperatures and strain rates to understand the characteristics of dynamic strain aging (DSA) in SA106 Gr.C piping steel and to estimate the effect of DSA on the material properties for leak-before-break (LBB) analysis. The manifestations of DSA were clearly observed in the tensile properties. However, the magnitude of serration and strength increase by DSA was relatively small compared to similar grade carbon steels. This may be due to high manganese content in the material. The variation in strain rate did not have a significant effect on the sigma(ys) at the nuclear reactor operating temperature which falls in DSA region. Ramberg-Osgood parameter n decreased in the region of DSA, and increased with increasing strain rate near the plant operating temperature. The influence of DSA manifested in Ramberg-Osgood parameter alpha was similar to that in sigma(ys). But, it was less clear than that on sigma(ys) and parameter n. Crack initiation resistance, J(i), and crack growth in a resistance, dJ/da, in DSA region were about 30-40% lower than those at RT, and showed the negative loading rate dependence. (C) 1997 Elsevier Science S.A.