CTOA Testing of Thick DWTT Specimens: Experiment and FEA Simulation for Development of an Annex for ASTM E3039
Bibliographic record
Abstract
Abstract ASTM E3039-16, Standard Test Method for Determination of Crack-Tip-Opening Angle of Pipe Steels Using DWTT Specimens (superseded), is limited to drop-weight tear test (DWTT) specimens with thickness B in the range 6–20 mm. There is a trend in the pipeline industry toward heavier wall pipe in the range of 25-mm thickness; hence, there is a need to test thicker DWTT specimens for crack propagation resistance. To address this need, proportionally larger DWTT geometry is proposed to allow a larger steady-state region with the same analysis procedure as in ASTM E3039. To support the development of an E3039 Annex, tests of an X70 pipe steel with B = 26.8 mm were performed at quasistatic and intermediate rates. The critical crack-tip-opening angle (CTOAB/2) of 15.0° ± 1.7°, estimated according to ASTM E3039, was close to the CTOA of 14.7° measured at midthickness sections. The effect on CTOA of varying the loading rate between 5 × 10−5 m/s and 0.1 m/s was found to be negligible. Fracture surfaces of specimens interrupted during testing showed severe crack tunneling. Finite element analysis simulations of crack propagation using a damage-mechanics model were performed on standard and proportionally large DWTT specimens to derive and compare CTOAs. These results show that ASTM E3039 can be applied successfully with proportionally scaled specimens to measure CTOA for steels of thicknesses significantly larger than 20 mm.
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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 | 0.001 | 0.001 |
| 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) | 0.000 | 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".