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Ultrasonic propagation in finite-length granular chains
D A Hutchins1, J Yang1, O Akanji1
1School of Engineering, University of Warwick, CV4 7AL, UK.
Ultrasonics
|November 10, 2015
Summary
Researchers generated solitary wave impulses in sphere chains using ultrasound. Strong non-linear effects at low pre-compression forces enable impulse train generation from sinusoidal inputs, matching theoretical models.
Area of Science:
- Nonlinear dynamics
- Acoustics
- Condensed matter physics
Background:
- Solitary waves exhibit particle-like properties and maintain their shape.
- Nonlinear systems can generate complex behaviors, including frequency generation.
Purpose of the Study:
- Investigate solitary wave impulse generation in finite-length sphere chains.
- Explore the influence of input parameters and physical properties on impulse formation.
- Validate a theoretical model for nonlinear wave propagation in discrete systems.
Main Methods:
- Utilized a narrowband ultrasound source to excite sphere chains.
- Systematically varied input signal amplitude, waveform, and static pre-compression force.
- Analyzed system response, including generated harmonics and sub-harmonics.
- Employed a theoretical model based on discrete dynamic equations.
Main Results:
- Successfully generated solitary wave impulses from a sinusoidal input.
- Observed the creation of harmonics and sub-harmonics as nonlinear normal modes.
- Impulse generation was critically dependent on very small pre-compression forces (approx. 0.01N).
- Experimental results showed strong agreement with the theoretical model predictions.
Conclusions:
- Finite-length chains of spheres can generate solitary wave impulses under specific nonlinear conditions.
- Low pre-compression forces are essential for observing strongly nonlinear behavior and impulse formation.
- The discrete dynamic model accurately predicts the observed wave phenomena in these systems.
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