Mode I Fracture Testing on Zirconium Foils Under Plane-stress Condition
Bibliographic record
Abstract
Zirconium alloys are commonly used in nuclear reactor in-core components due to their good mechanical properties and low neutron-absorption cross-section. Especially for CANada Deuterium Uranium (CANDU) reactors, zirconium alloys serve as the main structural material for fuel channels. In order to ensure such Zr components operate safely, fracture analysis of Zr alloys has been widely studied. Considering the high cost and difficulties associated with using neutron-irradiated Zr specimens for fracture analysis, proton irradiated testing has been proposed to reduce the cost and maintain a good control of experimental conditions during irradiation. However, limited by the proton penetration depth, fracture testing on proton-irradiated samples needs to be conducted on thin foils which brings increased plastic deformation due to the low constraint. This dissertation mainly focuses on conducting fracture testing with Zr foils. Combined with finite element modeling, scanning electron microscopy analysis, and digital image correlation analysis, the fracture behavior at a crack tip from both macroscopic strain analysis and microscopic dislocation motion analysis was achieved. The current study is comprised of three manuscript chapters. The Mode I fracture testing of Zr foils under plane-stress conditions is discussed in Chapter 3. Using conventional fracture testing combined with digital image correlation analysis, the J-integral, J-resistance curves and the singular strain field in front of a crack were all obtained. In Chapter 4, the dislocation evolution at the crack-tip field was analyzed during the crack initiation and propagation stages from a microscopic perspective. Both fracture toughness J-integral analysis and geometrically necessary dislocation determination indicate a single J-integral characterized crack-tip field may exist in Zr foils regardless of the large scale yielding condition. The crack propagation behavior was investigated from a crystallographic view in Chapter 5. Schmid factor analysis were compared with the geometrically necessary dislocation determination and relatively good agreement was observed. It was found that the crack is more likely to propagate along grains with c-axis close to the loading axis. A general discussion is given in Chapter 6, followed by a summary in Chapter 7.
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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 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| 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".