An Experimental Investigation of Acoustic Band Gaps and Localization in Granular Elastic Chains
Bibliographic record
Abstract
We assembled a chain composed of a periodic arrangement of aluminum and steel spheres encased in a 4-rod polycarbonate holder with tunable static precompression applied by means of a lever actuated system. To excite periodic oscillations we perturbed the chain with a piezo-stack actuator driven by both continuous and finite bursts of a sinusoidally varying periodic signal. The amplitude of the periodic signal ranged from linear to strongly nonlinear regimes. We report the tunability of the frequency range for the band gap edges as a function of the material parameters, chain geometry and stress conditioning. We analyze the data by means of force-time plot and Fast Fourier Transforms (FFT). We observe a dramatic reduction of the transmitted wave amplitude for harmonic excitations with fundamental frequencies within the gap. The application of both continuous and short bursts of perturbation allows for observation of different dynamic phenomena at selected frequency ranges (in particular close to the lower optical branch edge). By varying the amplitude of the dynamic excitation (and therefore the level of the nonlinearity present in the system) we seek localized discrete breathing modes and surface instabilities. The comparison between continuum theory, discrete numerical modeling and experiments show a qualitative agreement and provide fundamental understanding for future investigation and numerous engineering applications. The challenges and considerations involved with the construction of an experimental system capable of capturing and leveraging on the described phenomena will be detailed.
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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".