Double-channel, frequency-steered acoustic transducer with 2-D imaging capabilities

Area of Science:

• Acoustics
• Materials Science
• Non-destructive Testing

Background:

• Guided wave inspection is crucial for detecting damage in structural materials.
• Traditional methods often require complex transducer arrays for effective imaging.
• A need exists for advanced acoustic devices capable of precise beam steering and source localization.

Purpose of the Study:

• To introduce and validate a frequency-steerable acoustic transducer (FSAT) for guided wave-based damage imaging.
• To develop signal processing algorithms for localizing acoustic sources and scatterers using FSAT.
• To demonstrate the FSAT's capability for structural health monitoring applications.

Main Methods:

• Utilized a spiral-shaped FSAT array with unique wavenumber space distribution.
• Developed ad hoc signal processing algorithms involving spectrogram analysis and frequency warping.
• Applied frequency-angle mapping for localization in pitch-catch and pulse-echo configurations.
• Validated through numerical simulations and experimental measurements using a scanning laser Doppler vibrometer.

Main Results:

• Demonstrated the frequency-dependent directional properties of the spiral FSAT.
• Successfully localized acoustic sources and scatterers with the developed algorithms.
• Confirmed the effectiveness of FSAT for imaging damage in a two-dimensional half-plane.
• Experimental validation showed promising results for practical applications.

Conclusions:

• The spiral FSAT offers efficient beam steering with a single two-channel device.
• FSAT technology is suitable for frequency-selective acoustic sensing and broadband event localization.
• The FSAT shows potential for directional Lamb wave generation in structural health monitoring.