Stress-Corrosion Crack Initiation in X-52 Pipeline Steel in Near-Neutral pH Solution
Notice bibliographique
Résumé
Specimens from a failed X-52 pipeline that had been inservice for 34 years were pitted using the passivation/immersion method developed by the authors to simulate pitted pipelines observed in service. The resulting pitted samples were then cyclically loaded in an aqueous near-neutral pH environment sparged with 5% CO2 / balance N2 gas mixture at high stress ratios (minimum stress/maximum stress), low strain rates and low frequencies which were close to those experienced in service. It was found that the majority of cracks initiated from the corrosion pits and were less than 0.5 to 0.6 mm deep and were generally quite blunt. These cracks were transgranular in nature and designated as Stage I cracks and were typical of cracks found in most crack colonies. However, the further growth of these short, blunt cracks was significantly influenced by the distribution of the nearby non-metallic inclusions. Inclusions enhanced the stress-facilitated dissolution crack growth, which is the crack growth method proposed by the authors in a related paper. When the orientation of the inclusions was at a small acute angle to the orientation of the pits or cracks, and the inclusions were in the same plane as crack initiation or advance, these inclusions would enhance crack growth, or even trap hydrogen which further resulted in the formation of clusters of tiny cracks, which appeared to be caused by hydrogen. The hydrogen-produced cracks could be eaten away later by the stress-facilitated further dissolution of the blunt cracks. If these cracks can grow sufficiently however they pose an integrity risk, as they can initiate long cracks (near-neutral pH SCC). These hydrogen-caused cracks in Stage I were rare. It was nevertheless suggested that cracks deeper than 0.5 to 0.6 mm in the field should be removed to reduce or avoid the threat of rupture. If active corrosion and hydrogen generation can be prevented then smaller cracks are innocuous.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,010 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; les deux têtes enseignantes s’accordent sur ce qui est montré ici.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».