Upgraded Two-Step-Scaling Approach to the DTB Characterization of Ferritic Steels

Abstract

The fracture toughness of ferritic steels in the DTB (ductile-to-brittle) transition temperature region is a stochastic extrinsic property known for pronounced experimental data scatter that necessitates statistical approach in the DTB characterization. The novel two-step-scaling (2SS) method, proposed recently for the size effect-modeling across the DTB transition region, is developed based on the weakest-link statistics and the two-parametric Weibull distribution. Specifically, the size sensitivity of the Weibull parameters of scale and shape are built into the appropriate framework. This approach is upgraded in this article to render the comparison with the existing models more transparent. Specifically, the original 2SS method is enhanced by adding a lower limit on fracture toughness, resulting in the translated (three-parameter) Weibull cumulative distribution function. This third Weibull parameter, often dubbed the location parameter, defines a threshold value that limits the accessible fracture toughness domain. The upgraded 2SS approach is compared to two established methods of the DTB fracture toughness assessment, which favorably reflected upon its generality and application flexibility.