Finite element analysis of transient non-linear coupled field problems
Bibliographic record
Abstract
With recent advances in cornputer software and hardware technology, numerical simulation of transient nonlinear coupled field problems is becorning l e s costly and less time consuming than anaiyticai and experimental study.Thus many problems of economic importance can be addressed with transient nonlinear finite element analysis which canriot be addressed experiment=iily, for example because the scale on which they occur is too small for experirnental study.To address such problems.a 2-D M t e element program has b e n developed for the numerical study of transient nonlinear coupled (electrical, magnetic.theand mechanical) field problems.The program uses the Crank-Nicolson tirne stepping scheme for the tirne dornain discretization with adaptive time-stepping.accommodates position.field, and temperature-dependent material properties.time-dependent boundaxy conditions (e.g., time-dependent applied voltage).and allows couphg of at least two fields.e.g., electric and thermal.The program has k e n tested against experimental data in several contexts, with good agreement.The program has k e n applied successfully to the analysis of defect-induced high electric field phenomena fn cross linked polyethylene (XLPE).conversion of water trees to electrical trees in distribution cable.and electro-thermal phenomena in Z n 0 swge arrester disks, magnetic losses in pipe-type cable.etc.During studies of high field phenomena in XLPE electrfc and mechanical fields were cornputed in the vicinity of a conducting defect for a wide range of conditions, including AC and impulse waveforrns.The study shows that substantial mechanical stresses are generated by the thermally-induced expansion of the XLPE during an impulse.and the space charge-induced local temperature rise also causes the yield stress of XLPE to drop precipitously as the XLPE crystailites melt.Melding of the XLPE is likely to create a cavity surroundlng the defect which is capable of supportlng partial discharge.Field experience indicated that lightning impulses can convert water trees to electrical trees which then grow to failure.The numerical study suggests that during a lightning impulse.polarization current in the water within a water tree channel can cause the water temperature to rise to the point that the water pressure causes the XLPE to yield.generattng a cavity large enough to support partial discharge, which would lead to conversion of the water tree to a fault-inducing electrical tree.Pipe type transmission power cables are based on a dielectric fluid-filled steel pipe which contatns the three cable phases.Magnetic losses in the pipe are a significant factor in thermal design of such systems.However. the permeabliity of the pipe is strongly field-dependent.which.combined with the three phase current within the pipe.makes computation of pipe losses difficult.Pipe loss computations with the tram sient non1.inea.rfield program have produced good agreement with available data, and we have been able to extend computations to the case of unbalanceci phase currents which could not be computed previously.The nonlinear 1-V characteristic of Z n 0 is used to protect everything fkom consumer products to high voltage transmission systems fiom transient over-voltages.The large magnitude and short duration of lightning current impulses causes nonuniform heating of Z n 0 elemenl.Numerical studies show that mechanical stress causeci by lot-d thermal expansion can cause damage or failure of the Z n 0 disk.Nonlinear aspects of this computation include the field-dependent conductivity, temperature-dependent heat capacity, and temperature-dependent thermal conductivity of the ZnO.Computations of the thermal fields and resulting mechanical stresses have provideci u s e N data for Z n 0 disk design.As a result of this work.the energy absorption capability of commercial Z n 0 disks has been increased by 50%.1 wish to express my sincere gratitude and appreciation to Prof. S. A. Boggs.my thesis
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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) | 0.000 | 0.000 |
| 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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.159 | 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".