Residual life assessment of welded joints in the girth weld root

Abstract

<jats:p>The article analyzes the influence of the structural crack-like defect in the girth weld root welding the bottom to the collector body on the crack growth resistance. A mathematical model has been developed to estimate the residual life resource of welded joints with an internal crack-like defect in the root of the weld under creep. Results of metallographic studies of bench tests results for the welded joints long-term strength formed the basis of the calculation model. In all tested models the cracks start at the top of the narrow structural gap in the weld root and develop along almost the entire weld axis, perpendicular to the wall of the pipe and have a discrete growth pattern. As a result, discrete rupture of material occurs on a length of rc, and the initial crack is incremented by this length. After that, a “plastic core” of rc length is formed in the newly formed crack tip, additional damage is accumulated, and the crack development process continues until the stress level in the section weakened by the crack reaches a critical value. The obtained dependence characterizes the crack growth time from the initial crack-like defect to its critical length.</jats:p>

Fatigue and burst tests of full-scale girth welded pipeline sections for safe operations

“…Data and databases, pre-eminently the experimental data, have a determinant role in the integrity assessment and integrity management of different structural elements, structures and technical systems, as pipelines and pipeline systems [46,47]. With the help of these data and databases, and using the experimental data with critical approach, -integrity management systems can be established [48][49][50][51]; -integrity assessment and residual life-time calculations can be achieved [52]; -guidelines or rules can be established [53,54]; -survival models can be developed [55]; -and last but not least, management decisions can be made [56,57].…”