Fracture in Wrinkled Linepipe Under Monotonic Loading
Bibliographic record
Abstract
Buried pipelines may undergo large deformations due to geotechnical movements, temperature effects, and fluid pressure which result in axial loads, shear loads, moments and various complex combinations of these loads and load histories. Consequently, localized buckles and wrinkles may form in the pipe wall and, subsequently, fractures may develop at wrinkle locations. Previous research showed that large deformation due to monotonically applied symmetric loading can produce accordion type wrinkle geometry but fracture is not normally produced unless strain reversals at the wrinkle location occur due to the application of variable loads. Recently, a field fracture that developed in an NPS10 pipe was brought to University of Alberta Structures Laboratory for investigation. From the description of the load history at the failure location, and the inspection of the deformed geometry and fracture surface, it was recognized that no significant strain reversals had occurred in this particular wrinkled pipe segment. Examination implied that the final failure was a “tearing” failure resulting from monotonic application of a longitudinal load not aligned with the axis of the pipe. However, the true load history that caused the pipe to fracture at the wrinkle location was unknown. To verify the nature of the failure mechanism, and determine the characteristics contributing to its formation, it was felt necessary to attempt to reproduce similar failures in a wrinkle by subjecting it simultaneously to monotonically applied axial load and shear. Two full-scale tests applying axial load, and a shear load with different boundary conditions were carried out on NPS12 pipe. The second test produced a deformed geometry and a fracture configuration very similar to the one that developed in the field. This paper describes the test procedure for these two tests and the mechanics of the fracture. It is concluded that, with the appropriate load history and boundary conditions, fractures can be triggered at wrinkle locations by monotonic loading histories.
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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 | 0.001 |
| 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 | 0.001 |
| 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".