Single-mode Lamb wave excitation at high-frequency-thickness products using a conventional linear array transducer

Area of Science:

• Non-destructive testing
• Ultrasonic guided waves
• Phased array signal processing

Background:

• High-frequency-thickness products in Lamb wave excitation offer potential for high-resolution guided wave testing.
• Applications include crack imaging and corrosion mapping in difficult-to-access locations.
• Signal interpretation is complicated by the propagation of multiple Lamb wave modes.

Purpose of the Study:

• To systematically determine the influence of key parameters on single higher-order Lamb wave mode excitation.
• To enhance the purity of a targeted Lamb wave mode using a conventional linear array transducer.
• To apply phased array analysis tools to guided wave excitation for improved signal clarity.

Main Methods:

• Derivation of an analytical solution based on modal analysis.
• Decomposition of guided wave mode amplitude into single element response and excitation spectrum.
• Association of excitation spectrum with bulk wave phased array directivity function.
• Minimization of spectrum bandwidth, elimination of grating lobes, and derivation of an apodisation profile.

Main Results:

• Demonstration of a systematic approach for single higher-order Lamb wave mode excitation.
• Validation of theoretical results through experiments on an aluminum plate.
• Successful acquisition of the Full Matrix and synthetic reconstruction of signals.

Conclusions:

• The presented method effectively enhances the purity of targeted Lamb wave modes.
• This approach improves signal interpretation in guided wave testing.
• Optimized phased array techniques are crucial for advanced non-destructive evaluation applications.