A Procedure to Include the Additional Fatigue Effects of Thermal Gradients in a B31.1 Butt Weld of Dissimilar Metals and Welding End Transition of Similar Metals for Design and Plant Life Extension
Bibliographic record
Abstract
Fatigue evaluation in B31.1-2007 is currently done in accordance with para. 102.3.2 and generally considers only the stresses due to displacement load ranges and other cyclic loads. Yet fatigue damage is also occurring due to thermal gradients which are not considered. To exacerbate and complicate this additional type of fatigue damage, power plant design pressures and temperatures are rising, new materials are being introduced, pipes and attached components are becoming increasingly thick, and owners are requiring power plants to heat-up and cool-down at faster rates. Also, power plant owners are more and more interested in extending the life of power plants beyond their original design life. Although the fatigue design of ASME nuclear Class 1 piping components has long required thermal gradients to be considered, no attempt has been made to incorporate this knowledge into the B31.1 Power Piping Code (other than Creates, D. H., 2009, “A Procedure to Evaluate a B31.1 Welding End Transition Joint to Include the Fatigue Effects of Thermal Gradients for Design and Plant Life Extension,” PVP2009-77148, Proceedings of the ASME 2009 Pressure Vessels and Piping Conference, Volume 3, Design and Analysis, A. Segall, ed., ASME, New York, PVP-Vol. 3, pp. 101–110). To address this pressing need in today’s power plant environment this paper now provides a fully comprehensive methodology for assessing an “as-welded” Butt weld of dissimilar metals and a Welding End Transition (B31.1-2007, Fig. 127.4.2) of similar metals to include the additional fatigue effects of thermal gradients calculated in accordance with ASME Section III-2007 Subarticle NB-3600. The disadvantage of this approach is that the conservatism in these calculations may produce unacceptable results. In that case, this assessment is a warning that something else needs to be done by way of monitoring, modifying the design or the thermal operation, or performing a more rigorous evaluation. The advantage of this methodology is that it maintains the traditional B31.1 approach to fatigue with the same limit of SA except that there is now an additional term, STG, to account for the fatigue contribution due to thermal gradients. Considering the effects of thermal gradients in this way will further help to preserve the integrity of the piping pressure boundary and consequently, the safety of personnel in today’s power plants and into the future.
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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 | 0.000 |
| 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) | 0.000 | 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".