Mezzo-scopic Analysis of Fracture Toughness in Steels

Abstract

The cleavage fracture toughness of steels was mezzo-scopically analyzed on the basis of the statistical local fracture criterion approach. The statistical stress criterion at the crack tip region suggests that the cleavage fracture toughness in steels can be described as a function of the yield stress, the cleavage fracture stress, and other mechanical properties of the materials. Formulation of the cleavage fracture toughness was first examined through an investigation on correlation between the cleavage toughness and the cleavage fracture stress obtained in notched round bar specimens in accordance with the theoretical prediction. Then, the scatter of the toughness, specimen thickness effect on the toughness, deterioration of the toughness due to cold working and irradiation, and improvement of the toughness caused by the Ni addition, were analyzed through the formulation of the toughness.

Reliability research of reference temperature estimation of RPV materials using Charpy impact energy

“…Based on Miyata and Tagawa's research [22] about the relations between micro-cleavage fracture stress (σ f , a given steel constant), yield stress and fracture toughness, Sreenivasan defined two new parameters, P IGC1 and P IGC2 [19], as follows:…”

“…The yield strength data of 16MnDR and the rest three materials [26] are fitted and shown in Eqs. (21)(22)(23)(24) respectively:…”

“…A508-3∶ ys (MPa) = 0.0013 ⋅ T 2 − 0.6171 ⋅ T + 462.58(22) A533B∶ ys (MPa) = 0.0074 ⋅ T 2 − 0.2386 ⋅ T + 493.1278(23) 20MnMoNi55∶ ys (MPa) = 0.0112 ⋅ T 2 − 0.0431 ⋅ T + 494.01(24) 16MnDR∶ ys (MPa) = 380.41 − 0.6633 ⋅ T…”