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DC effects, sub-harmonics, stochasticity and "memory" for contact acoustic non-linearity
B A Korshak1, I Yu Solodov, E M Ballad
1Department of Physics, Moscow State University, Russia.
Ultrasonics
|August 6, 2002
Summary
Non-linear acoustic waves interacting with contacts generate unique elastic fields and phenomena like amplitude hysteresis. This acoustic non-linearity in solids can store information for hours, potentially useful for defect detection.
Area of Science:
- Solid Mechanics
- Acoustics
- Non-linear Dynamics
Background:
- Acoustic wave interaction with non-bonded contacts exhibits inherent non-linearity.
- Asymmetrical stiffness distribution across interfaces is a key factor.
- This non-linearity generates local static elastic fields within contacts.
Purpose of the Study:
- To investigate the non-linear acoustic phenomena arising from contact interactions.
- To explore the potential for information storage in cracked flaws.
- To understand the mechanisms behind acoustic non-linearity and its manifestations.
Main Methods:
- Analysis of acoustic wave interaction with non-bonded contacts.
- Parametric modulation of contact stiffness to induce non-linear effects.
- Observation and characterization of phenomena such as hysteresis and memory effects.
Main Results:
- Diode-type non-linearity produces transient DC-acoustic pulses.
- Contact stiffness modulation leads to acoustic instability, sub-harmonics, and chaotic excitations.
- Realistic cracked flaws show amplitude hysteresis and storage lasting hours, linked to micro-strain relaxation.
Conclusions:
- Acoustic non-linearity in contacts is a rich source of complex wave phenomena.
- The observed long-term non-linear memory in cracks has implications for non-destructive evaluation.
- Slow relaxation of thermally induced micro-strain is a likely mechanism for information storage.