RECENT ADVANCES IN THE FATIGUE ASSESSMENT OF WELD IMPERFECTIONS

Abstract

Fitness-for-purpose is now widely accepted as the most rational basis for the assessment of weld imperfections, such that an imperfection would need to be repaired only if its presence was harmful to the integrity of the member or structure. When considering the integrity of a welded structure it may be necessary to consider a number of potential failure modes, including static fracture, creep, stress corrosion and buckling, but the one which proves to be the most sensitive to weld imperfections is fatigue. Much of the groundwork which went into the derivation of the fatigue recommendations in PD 6493 was carried out by a working group of International Institute of Welding (IIW) Commission XIII. In 1978, the IIW adopted these recommendations and transmitted then to ISO for information. At the same time, it decided to produce its own guidance on the acceptance of weld imperfections and, following collaboration between Commissions V (nondestructive testing), X (fracture), XIII (fatigue) and XV (design), a draft was agreed to in 1989, and subsequently published. The earlier fatigue recommendations have been reviewed to take account of more recent research and of experience gained in the application of PD 6493. This paper outlines the new recommendations andmore » discusses the background to the main new features.« less