Fracture Toughness Assessment of Present and Future Pressure Vessel MaterialsBased on Charpy Impact Energy and Yield Strength

摘要

Several medium and high strength alloys, including AF1410, Inconel 718, PH 13-8Mo stainless steel, and ASm A723 high strength low alloy steel, have been heat treated to various strength and toughness levels and evaluated for correlations between fracture toughness and charpy impact energy. The correlations investigated included those by Roffe-Novak and Ault-Wald-Bertolo. previous work by Kapp and Underwood suggests that for A723 steel, the Rolfe-Novak correlation predicts the fracture toughness reasonably well. One potential limitation of their study was that the charpy impact energy was measured at -40 deg f, whereas the toughness was evaluated at room temperature. This study evaluates Charpy impact energy and toughness at both room temperature and at -40 deg F and considers both when utilizing these correlations. Results of this study indicate that the Rolfe-Novak correlation over-predicts the measured fracture toughness at room temperature, and tends to underpredict the measured fracture toughness at 40 deg F. The Ault-Wald-Bertolo correlation, in all but one instance, was a conservative estimate of the measured fracture toughness of the material at both room temperature and 40 deg F. Utilizing the results presented in this study, it is recommended that if a correlation is necessary for estimating the toughness of any of the materials, the Ault-Wald-Bertolo correlation will result in a conservative estimate of toughness. (MM).