Experimental and In-Service Observations of HIC Nucleation and Growth in Pipeline Steel
Bibliographic record
Abstract
Abstract This paper presents the results of experimental and in-service observations of the nucleation and growth of hydrogen-induced cracking (HIC) in hydrocarbon transport pipelines made of type API 5L steel. The experimental work was done by inducing HIC on steel plates by electrochemical cathodic hydrogen charging and using a straight beam ultrasonic inspection technique to observe the crack growth behavior. Scanning electron microscopy was also used to observe the crack nucleation and propagation mechanisms. The study was complemented by the fractographic analysis of a pipe segment removed from a sour gas pipeline after an in-service rupture caused by HIC, so the pipe segment contained a significant group of blisters and laminations caused by HIC. The results of the cathodic charging indicated that HIC cracks nucleated in less than one hour of hydrogen charging at specific non-metallic inclusions and not necessarily the largest ones as commonly thought. It is observed that the HIC cracks propagated by a quasi-cleavage mechanism in transgranular paths, linking to other cracks by ductile tearing. However, after a few hours of hydrogen charging, the crack growth rate dropped to almost zero, and the overall HIC growth was due almost solely to the interconnection of previously formed individual cracks. The examination of the in-service failed pipe showed similar fractographic and growth characteristics as compared to the laboratory-induced ones. It showed that HIC was little affected by the primary stresses and the proximity of other defects and structural discontinuities.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".