Evaluation of the Elastic-Plastic Fracture Mechanics Methodology on the Basis of Large-Scale Specimens

Abstract

Within the scope of the cooperative project “Integrity of Components” (FKS) which is a part of the German Nuclear Safety Research Programme of the Federal Minister for Research and Technology, the theoretical and experimental investigation on ductile fracture is of decisive importance. The FKS is mainly concentrated on tearing tests on large-scale heavy-section specimens, in both the base material and welded conditions. Universal facilities up to 100 MN are available to test large-scale round and flat bars containing sharp defects in the form of machined notches, fatigue cracks, and natural flaws, such as segregation and heat-affected zone cracking. The dimensions are chosen so that it is possible to realize the significant technological states of material and stress over all conditions in the light-water reactor pressure vessel. The tested materials similar to A508 Class 2 and 3 cover a wide range of ductility (Cv upper-shelf toughness-40 to 200 J, crack initiation Ji = 50 to 200 kN/m, T-modulus = 10 to 300).

On the fitting and extrapolation of J‐resistance data derived through the linear normalization technique

“…Notice in this plot that the initiation J i criterion is fairly conservative when compared to J 50 . On the other hand, it has been shown analytically and experimentally 8,13 that the latter criterion predicts adequately conservative estimations of the real ductile instability conditions of intermediate to full-scale flawed vessels internally pressurized till failure.…”