Piercing soft solids: A mechanical theory for needle insertion
Bibliographic record
Abstract
In this paper we investigate the mechanical problem of piercing a soft solid\nbody with a needle. This phenomenon is controlled by the critical condition of\nneedle insertion. Needle insertion involves physical and geometrical\nnonlinearities and a complex failure mechanism. To overcome the complexity of\nthe problem, we describe needle insertion as a sharp transition between two\nneedle-specimen configurations, namely "indentation" and "penetration". The\nsharp configurational change emerges from a mechanical instability and follows\nthe principle of energy minimum. We describe the needle-specimen system in\nterms of the force applied to the back of the needle and the axial displacement\nof the needle tip toward the material. At small needle displacements, the\nenergetically favoured configuration is indentation. Conversely, when the\nneedle displaces beyond a critical threshold, it penetrates the specimen by\nrupturing its surface. This creates a new energetically favoured configuration:\npenetration. Our analysis considers a cylindrical needle with a spherical tip,\nneglects friction and adhesion between the needle and the material, and assumes\nquasi-static conditions. Despite the mathematical simplicity of our analysis,\nour theoretical predictions on the needle insertion force have been validated\nagainst experiments with surprising accuracy. Our method provides an effective\npredictive tool, which can be extended to account for different indenter\ngeometry and material behaviour.\n
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.001 |
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".