Improved Failure Assessment Diagrams to Describe Delayed Hydride Cracking Initiation at a Blunt Flaw
Bibliographic record
Abstract
Delayed Hydride Cracking (DHC) in Zr-2.5 Nb alloy material is of interest to the CANDU (CANada Deuterium Uranium) industry in the context of the potential to initiate DHC at a blunt flaw in a CANDU nuclear reactor pressure tube. The material is susceptible to DHC when a hybrided region forms at the flaw tip. The hydrided region could then fracture to the extent that a crack forms, and is able to grow by the DHC crack growth mechanism. A process-zone based methodology for evaluation of DHC initiation at a blunt flaw that takes into account flaw geometry has been developed. In a paper presented at the 2000 ASME PVP Conference, the process-zone methodology was used to develop failure assessment diagrams in such a way that the geometry dependence of the failure assessment curves was minimized. This was achieved by defining the ordinate of the failure assessment diagrams in terms of the ratio of the applied elastic peak stress divided by the threshold peak stress for DHC initiation at the tip of a deep flaw. However, the resultant failure assessment curves for Mode I loading did not have the simple form as the curves for Mode III loading, where the Mode III case was modelled in order to clearly see the interplay between material and geometry parameters. The present paper demonstrates that the irregular shapes of the Mode I curves were due to the relation for the threshold peak stress for the deep flaw that was used in the Mode I failure assessment curves. In the 2000 ASME PVP Conference paper an exact relation for the threshold peak stress was used for Mode III loading, while an approximate relation was used for Mode I. In the present paper a more accurate relation for the threshold peak stress for a deep flaw was used for Mode I loading, and the resultant Mode I failure assessment curves have a simpler form, which leads to more practical applications of the approach. Agreement between the improved Mode I failure assessment diagram predictions and experimental results is reasonable.
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.002 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.003 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
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".