Air-Coupled and Resonant Pulse-Echo Ultrasonic Technique

Area of Science:

• Materials Science
• Nondestructive Testing
• Acoustics

Background:

• Traditional ultrasonic nondestructive testing (NDT) methods face limitations with certain materials and geometries.
• The 'dead zone' near the surface in pulse-echo techniques hinders early flaw detection.
• Materials with high acoustic impedance and low attenuation are challenging for conventional NDT.

Purpose of the Study:

• To present a novel air-coupled ultrasonic resonant pulse-echo NDT technique.
• To overcome the dead zone issue by analyzing resonant echoes.
• To determine material properties like velocity and thickness using resonant frequencies.

Main Methods:

• Utilized wideband air-coupled transducers for excitation and reception.
• Employed resonant mode excitation in components with regular geometries.
• Analyzed received echoes in the frequency domain to identify resonant frequencies.

Main Results:

• Successfully tested on steel, aluminum, and silicone rubber plates, demonstrating effectiveness with high acoustic impedance and low attenuation materials.
• Achieved accurate thickness and velocity measurements by analyzing resonant frequencies.
• Showcased the technique's ability to generate C-Scan images and its sensitivity to incidence angle variations.

Conclusions:

• The developed air-coupled ultrasonic resonant NDT technique is effective for components with regular geometries and specific material properties.
• The method successfully mitigates the dead zone problem inherent in traditional pulse-echo techniques.
• This approach offers a viable alternative for material characterization and imaging in NDT applications.