Dynamic crack branching in anisotropic coal: a rate-dependent modeling approach and ABAQUS implementation
Bibliographic record
Abstract
Why cracks in rocks bifurcate under dynamic impact and how to accurately model bifurcation behavior affected by existed natural fractures are urgent issues that need to be addressed in the study of rock dynamic fragmentation in-depth. In this study, it is theoretically analysed that the relationship between crack surface separation strain rate and crack propagation speed according to the geometric configuration of dynamic crack propagation. A constitutive model to describe the propagation and bifurcation of dynamic brittle cracks is proposed based on the empirical fracture energy rate-dependent model, and this model is written as an ABAQUS user subroutine to model the fragmentation process of coal samples with bedding under Hopkinson bar impact with cohesive element method. For dynamic fracture problems, an approach for determining the cohesive element size is proposed, which combines the cohesive zone length with the Grid Convergence Index (GCI) method. The location and timing of crack initiation are further clarified at the μs scale. Results show that for the dynamic impact test of Brazilian disc (BD) sample with beddings, crack initiation lags behind stress wave for 30 s before dynamic balance state, and the macro fracture is formed by the intersection of multiple cracks, which is significantly different from that of static BD test. The complex stress environment in the BD sample with beddings makes the initiation law of dynamic cracks uncertain. The number of main crack has a significant correlation with impact velocity, thus the meaning of the dynamic tensile strength calculated based on SHPB test cannot represent the real dynamic tensile strength, which is influenced by the beddings.
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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) | 0.000 | 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".