Equivalent CTOD Concept for Correction of CTOD Toughness for Constraint Loss in Steel Weld Components

Abstract

This paper presents a new fracture assessment method, IST method developed as ISO 27306. The IST method implements an equivalent CTOD ratio, β, for the CTOD toughness correction for constraint loss in structural components. Using β, the standard fracture toughness specimen and structural components are linked at the same level of the Weibull stress. This paper extends the equivalent CTOD concept to weld components. Effects of the weld strength mismatch and residual stress on β are discussed. It is shown on the failure assessment diagram (FAD) that the CTOD toughness correction with β leads to accurate fracture assessments of weld panels, whereas the conventional procedure gives much conservative results.