Statistical re-evaluation of the ASME K-IC and K-IR fracture toughness reference curves

Historically the ASME reference curves have been treated as representing ab solute deterministic lower bound curves of fracture toughness. In reality, this is not the case. They represent only deterministic lower bound curves to a specific set of data, which represent a certain probability range. A r ecently developed statistical lower bound estimation method called the 'Mas ter curve', has been proposed as a candidate for a new lower bound referenc e curve concept. From a regulatory point of view, the master curve is somew hat problematic in that it does not claim to be an absolute deterministic l ower bound, but corresponds to a specific theoretical failure probability t hat can be chosen freely based on application. In order to be able to subst itute the old ASME reference curves with lower bound curves based on the ma ster curve concept, the inherent statistical nature (and confidence level) of the ASME reference curves must be revealed. In order to estimate the tru e inherent level of safety, represented by the reference curves, the origin al database was re-evaluated with statistical methods and compared to an an alysis based on the master curve concept. The analysis reveals that the 5% lower bound master curve has the same inherent degree of safety as original ly intended for the K-IC-reference curve. Similarly, the 1% lower bound mas ter curve corresponds to the K-IR-reference curve. (C) 1999 Elsevier Scienc e S.A. All rights reserved.