Nonlinear Vibrations of Woven Dacron Aortic Prostheses Conveying Pulsatile Flow
Bibliographic record
Abstract
Woven Dacron grafts represent standard implants for replacements of the thoracic aorta in current medical practice. Wide knowledge about the distinctly different mechanical properties of the Dacron implants with respect to the native aorta is available in literature while very little is known about the dynamic behavior of these prostheses. This study addresses the dynamic response to pulsatile physiological blood flow and pressure of woven Dacron grafts currently used in thoracic aortic replacements. The structural model assumes a cylindrical orthotropic shell described by means of the nonlinear Novozhilov shell theory. Residual stresses because of pulsatile physiological pressurization are evaluated and included in the model. The pulsatile flowing fluid is formulated using a hybrid model that contains the unsteady effects obtained from linear potential flow theory and the viscous effects obtained from the unsteady time-averaged Navier–Stokes equations. Physiological waveforms of blood pressure and velocity are approximated with the first eight harmonics of the corresponding Fourier series. Coupled fluid-structure Lagrange equations for a non-material volume with wave propagation in case of pulsatile flow are utilized. Frequency-response curves in the physiological range show the geometrically nonlinear vibration response to pulsatile flow with several superharmonic resonance peaks in the high physiological frequency range. Different values of modal damping are considered; in the limit case of low modal damping values, flow-induced asymmetric vibration of the aortic prosthesis is possible. Finally, in order to reproduce the weave design of the woven Dacron fabrics, geometric imperfections are introduced in the structural model. The numerical natural frequencies of the pressurized prosthesis are compared with the experimental results obtained from the modal analysis of a woven Dacron graft.
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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) | 0.000 | 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 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".