ASME Pressure Design of Class 1 Pipe Bends Using Elastic-Plastic FEA
Bibliographic record
Abstract
In a previous paper, it was demonstrated that a tight radius bend with uniform wall thickness equal to the pressure based thickness of the corresponding straight pipe does not meet the linear elastic criteria of NB-3221 Design Loadings. It was also demonstrated that the allowable wall thickness circumferential distribution of the ASME B&PV Code SEC XI Code Case N-597-2 achieves a uniform linear elastic stress intensity over the entire bend that meets the linear elastic criteria of NB-3221. As stated by the ASME B&PV Code under NB-3221, the provisions of NB-3228 may provide relief from certain of the linear elastic stress limits if plastic analysis techniques are applied. In this paper, the plastic collapse analysis approach of the COG FFSG is adopted to explore the relative safety margin when analyzing various Class 1 tight radius pipe bends’ configurations made of Carbon Steel SA-106 Grade B. In addition to the power law material model, three elastic plastic material models are constructed based on ASME B&PV Code Section II Part D material properties. The pressure-based thickness for the same size straight pipe is uniformly used in modelling the tight radius bends (no increased thickness on the intrados). It is demonstrated that the results from the ASME B&PV based flow stress model are marginal and that the ASME B&PV based bi-linear material model and the limit analysis results are not meeting the collapse pressure criterion. It is also demonstrated that the uniform pressure-based thickness along with the power law material model meets the requirements for the adopted plastic collapse pressure providing a considerable life extension.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
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".