Loading Rate Effect on the Master Curve Reference Temperature, T0, for the A533 B Material

The tests were carried out in displacement control at two temperatures, −70 and −60°C, and at three load rates, dK/dt=0.1, 1, and 10 MPam/s. The determined reference temperatures, T0 (0.1 MPam/s)=−73.6±6.4°C, T0 (1 MPam/s)=−63.3±5.4°C, and T0 (10 MPam/s)=−50.3±5°C, are similar to those obtained by other laboratories [IAEA Second Meeting on Master Curve to Monitor the Fracture Toughness of RPVs in NPPs, November 2006, Dresden, Germany]. The shift in T0 within the quasi-static loading rate interval (0.1–2 MPam/s) recommended by ASTM E1921-05 [“Standard Test Method for Determination of Reference Temperature, T0, for Ferritic Steels in the Transistion Range,” Annual Book of ASTM Standards, Vol. 03.01, ASTM International, West Conshohocken, PA.] is 14.4°C and the shift in T0 between decades of dK/dt on logarithmic scale is 11°C. The empirical relation proposed byWallin [“Effect of Strain Rate on the Fracture Toughness Reference Temperature T0 for Ferritic Steels,” Recent Advances in Fracture, R. K. Mahidhara et al., Eds., The Minerals, Metals and Materials Society, 1997, pp. 171–182] predicts very well the shift in T0 in the quasi-static loading regime (0.1–2 MPam/s). This work provides experimental support to limit the quasi-static loading rate interval in ASTM E1921.