Cubic nonlinearity parameter measurement and material degradation detection using nonlinear ultrasonic three-wave...

Area of Science:

• Materials Science
• Nonlinear Acoustics
• Structural Health Monitoring

Background:

• Early detection of structural damage is crucial for safety.
• Nonlinear ultrasonic techniques, measuring material nonlinearity, are key for degradation detection.
• Existing methods often focus on third-order elastic constants, but fourth-order constants are also relevant.

Purpose of the Study:

• To develop and validate a nonlinear ultrasonic three-wave mixing technique for generating and measuring third-order combined harmonics (TOCH).
• To assess the technique's capability in detecting material degradation by measuring the cubic nonlinearity parameter.
• To compare the sensitivity of this new method against existing nonlinear ultrasonic techniques for early-stage damage detection.

Main Methods:

• Development of a nonlinear ultrasonic three-wave mixing technique to generate TOCH in plate-like structures.
• Theoretical modeling of TOCH generation in nonlinear elastic plates.
• Experimental validation using intact and degraded aluminum specimens with varying degradation levels.

Main Results:

• A theoretical model for TOCH generation was developed and experimentally validated.
• Measurements successfully identified inherent material nonlinearity and degradation levels.
• The proposed three-wave mixing technique demonstrated superior sensitivity to early-stage material degradation compared to two-wave mixing and third harmonic generation.

Conclusions:

• The developed three-wave mixing technique effectively measures TOCH for assessing material nonlinearity and degradation.
• This method offers enhanced sensitivity for detecting early-stage material degradation in structures.
• The technique holds promise for improving structural safety through more effective damage detection.