Validation of Proposed Revised Master Curve Temperature Validity Limits Using Experimental Fracture Toughness Datasets

Abstract The Master Curve methodology, currently standardized in ASTM E1921-24, requires individual test temperatures to be within ±50 °C of the calculated reference temperature, T0. Meeting the lower validity limit, T0 – 50 °C, can be challenging for very small specimens, such as miniature C(T) or MC(T), on account of the typically low value of the specimen capacity, KJclim. Recently, Yamamoto, Kirk, and Shinko (Journal of Pressure Vessels Technology, 2024) proposed an alternative approach to the application of the lower temperature limit for the Master Curve methodology. According to this proposal, the average test temperature, Tave, for a given dataset, instead of each individual test temperature, should be higher than the lower validity limit, T0 – 50 °C, for the calculated reference temperature to be valid. This modified approach was originally validated using synthetic datasets generated by Monte Carlo simulations. In this study, the proposal has been validated using nine large publicly available “historical” fracture toughness datasets, as well as seven additional datasets found in the open literature. Additional analyses were conducted using the same Tave requirement with respect to the upper temperature validity limit (Tave ≤ T0 + 50 °C), as well as using both the lower and the upper validity limits (T0 – 50 °C ≤ Tave ≤ T0 + 50 °C). Finally, we also investigated a 2018 proposal by Wallin, who suggested a thickness-dependent lower temperature limit. All the results obtained in this investigation support modifying the current test temperature validity requirements in a future revision of ASTM E1921.