Growth of Surface-Type Stress Corrosion Cracks in Near-Neutral pH Environments Under Disbonded Coatings
Bibliographic record
Abstract
Near-neutral pH stress corrosion cracking (NNPHSCC), which occurs when ground water penetrates under the pipe coating, causes longitudinal cracks to develop on the surface of pipelines. Such cracks grow over time and can ultimately lead to pipeline failure. NNPHSCC is currently managed by in-line inspection or hydrostatic testing for oil and gas pipelines respectively. These procedures are enormously expensive and have to be repeated at predetermined intervals. Re-inspection intervals are currently determined by empirical models, which have been found rather imprecise. A major flaw in currently applied models is that they assume that once a NNPHSCC crack is formed, it grows at a constant rate that is independent of pipeline operating variables and both pre- and in-service history of the pipeline material. This is not necessarily true as pipeline history, the nature of the service environment and operating factors, among several other factors, have a strong influence on the rate of NNPHSCC crack propagation. Most existing models also treat NNPHSCC cracks as long through thickness cracks rather than surface type cracks typically observed in the field. This research proposes to provide an empirical model that more accurately predicts the growth rate of near-neutral pH SCC cracks in near-neutral pH environments by studying the growth rate of surface type flaws while also accounting for the influence of operating factors, environmental factors, coating disbondment and cathodic protection on the rate of crack propagation. This paper reports some preliminary test results obtained using a long specimen with three semi elliptical surface flaws located in three reduced sections to simulate field observed NNPHSCC cracks. Preliminary results suggest that: 1) crack grows much faster at the open mouth, which was attributed to hydrogen effects; 2) crack dormancy can occur under certain combined mechanical factors; 3) although the benign mechanical loading cannot lead to a direct crack growth (crack dormancy), it causes damage to the crack tip, which makes the crack more susceptible to crack growth upon a more aggressive condition is encountered.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.008 | 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 teacher head, 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".