Selective remote excitation of complex structures using time reversal in audible frequency range

Area of Science:

• Acoustics
• Materials Science
• Nondestructive Testing

Background:

• Elastic wave generation is critical for nondestructive testing (NDT) and structural health monitoring (SHM).
• Analyzing resonance spectra of thin elements aids SHM.
• Remote excitation of elastic elements is desirable for practical applications.

Purpose of the Study:

• To investigate elastic wave generation using a time reversal mirror (TRM).
• To study the impact of TRM geometry on wave focusing and excitation efficiency.
• To determine optimal configurations for selective excitation of structural components.

Main Methods:

• Utilized a time reversal mirror (TRM) operating in the audible frequency range (1-10 kHz).
• Studied the relationship between TRM geometry (number of loudspeakers) and elastic wave focusing.
• Estimated energetic efficiency of the TRM during air/plate coupling.
• Applied the DORT (decomposition of the time reversal operator) method for analysis.

Main Results:

• Wave focusing quality showed weak dependence on the number of loudspeakers in the TRM.
• Estimated energetic efficiency reached approximately 0.02% at maximum air/plate coupling.
• Demonstrated efficient and selective excitation of a small structure within a complex environment (hollow cylinder).
• Identified optimal loudspeaker placement and emission signals for exciting individual plate eigenmodes.

Conclusions:

• TRM is an effective tool for remote, selective elastic wave excitation in NDT and SHM.
• TRM performance is robust to variations in loudspeaker count.
• The DORT method provides insights for optimizing TRM configurations for specific excitation tasks.