Mechanism of grain refinement and its effect on Adiabatic Shear Bands in 4340 steel and pure copper during impact
Bibliographic record
Abstract
Pre-deformation and post-deformation microstructure characterization was conducted on tempered 4340 steel and commercial pure copper specimens under impact to determine the microstructural changes and the mechanism of grain refinement that occur during the evolution of ASBs. It was observed that the movement and multiplication of dislocations, elongation of grains, breaking of elongated grains, rotation, carbide fragmentation and boundary refinement of broken grains occur simultaneously during the evolution of ASBs in the impacted 4340 steel specimens. The extent of these mechanisms depends on the imposed local strain and strain rate. Extensive grain refinement coupled with high density of dislocations results in the shear band structures being more susceptible to crack nucleation and propagation. In copper, it was observed that sequential occurrence of emergence of dislocations, dislocation cell formations with varying cell boundaries and cell interiors, dynamic recovery and extensive micro-twinning results in the formation of the shear bands. The structure within the evolved shear bands becomes less brittle after the onset of dynamic recovery and micro-twinning. The differences in the mechanism of grain refinement and evolution of the shear bands in both materials is attributed to the differences in the mobility of dislocations, the rate of strain hardening and strain hardening exponents in both materials studied.
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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) | 0.001 | 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".