Residual Stress Modeling of Warm-Bent Tight-Radius CANDU Feeder Bends
Bibliographic record
Abstract
In one CANDU® nuclear station, a few feeder piping failures have occurred because of stress corrosion cracking. All the cracks were located in tight-radius bends. Root cause analyses indicated that the residual stress played a significant role in these failures. Residual stress measurements using the neutron diffraction technique have been performed to quantify the residual stresses for a large number of feeder bends. Numerical simulations have also been performed to supplement the measurement data. This paper presents the modeling work carried out for 2.5” warm-bent tight-radius feeder bends using LS-DYNA®. The warm-bending process was divided into heating, bending, springback and cooling stages. The simulation results were compared to the measurement data using the neutron diffraction technique. Good agreement was achieved between the trends of simulation results and the measured residual stresses in feeder bends. Additionally, it was found that the predicted cross-sectional shape and wall thickness distribution agreed well with the measurements. Limitations of the simulation work were summarized and recommendations for future research were made based on this study.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".