Highly Sensitive Detection of Microstructure Variation Using a Thickness Resonant Transducer and Pulse-Echo Third...

Area of Science:

• Materials Science
• Nonlinear Acoustics
• Ultrasonic Testing

Background:

• Nonlinear ultrasound testing offers sensitive detection of microstructural variations and damage.
• The cubic nonlinear parameter (γ') provides higher sensitivity than the quadratic nonlinear parameter (β') for nonlinear parameter mapping.
• Efficient generation and reception of the third harmonic are crucial due to its low amplitude.

Purpose of the Study:

• To explore an odd harmonic thickness resonant transducer for pulse-echo third harmonic generation (THG) measurements.
• To address and correct for source nonlinearity in THG measurements.
• To evaluate the sensitivity of γ' for detecting microstructural changes in aluminum specimens.

Main Methods:

• Measurement of γ' using through-transmission in aluminum specimens with varying thickness and input voltage.
• Application of an odd harmonic resonant transducer for pulse-echo THG measurements.
• Correction for attenuation, diffraction, and source nonlinearity effects.

Main Results:

• The odd harmonic resonant transducer effectively generates and detects fundamental and third harmonics.
• Highly sensitive detectability of γ' was demonstrated as a function of aging time in heat-treated specimens.
• The sensitivity of γ' was compared with that of β' and β'2, highlighting its advantages.

Conclusions:

• The developed odd harmonic resonant transducer is effective for pulse-echo THG measurements.
• The cubic nonlinear parameter (γ') offers superior sensitivity for nonlinear parameter mapping compared to β'.
• This technique shows promise for advanced material characterization and damage assessment.