Size, Geometry, and Material Effects in Fracture Toughness Testing of Irradiated Zr-2.5Nb Pressure Tube Material
Bibliographic record
Abstract
The effect of initial crack size on the crack growth resistance (J-R) curves determined from burst tests on irradiated Zr-2.5Nb pressure tubes has been studied and the results compared with those obtained from matched curved compact specimens. The study used sections from three different tubes representative of material of low, intermediate, and high toughness. In each case a series of burst tests was conducted at 250°C with different starting crack sizes (from 35 to 85 mm) followed by small specimen testing. The toughness was characterized by means of deformation J-R curves using the d-c potential drop method to measure stable crack growth. Fractographic studies were also conducted in support of the J-R curve results. For tubes of low to intermediate toughness there is little evidence of a crack size effect on the J-R curves from the burst tests. However, for burst tests on tubes of higher toughness there is an increase in out-of-plane bending associated with the wider crack openings (bulging) that can promote earlier failure by slant/shear instability and a lowering of the J-R curve. Thus the J-R curves from such tubes exhibit more variability in toughness as well as an apparent crack size dependence. Such crack growth behavior overrides any increase in material toughness with irradiation temperature as revealed by the small specimens.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.031 | 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 teacher head, 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".