Low-frequency Lamb wave mixing for fatigue damage evaluation using phase-reversal approach

Area of Science:

• Non-destructive testing
• Materials science
• Acoustic wave propagation

Background:

• Early-stage fatigue damage detection remains a significant challenge.
• Non-destructive evaluation (NDE) methods are crucial for assessing material integrity before critical failure.
• Lamb waves offer a promising approach for NDE due to their sensitivity to material changes.

Purpose of the Study:

• To evaluate early-stage fatigue damage using nonlinear wave mixing of Lamb waves.
• To investigate the sensitivity of combinational harmonics to material nonlinearities induced by fatigue.
• To assess the effectiveness of a phase reversal approach in improving damage evaluation.

Main Methods:

• Utilizing the wave mixing method with two fundamental symmetric mode (S0) Lamb waves at low frequencies.
• Employing a phase reversal technique to enhance signal quality and isolate specific harmonics.
• Conducting parametric studies with 3D finite element (FE) analysis to optimize excitation parameters.
• Validating numerical findings with experimental data on undamaged and cyclically loaded samples.

Main Results:

• Sum combinational harmonics and second harmonics are sensitive to weak material nonlinearities.
• The sum combinational harmonic demonstrates significantly higher sensitivity to progressive fatigue damage than second harmonics.
• The phase reversal approach effectively mitigates interference from undesirable harmonics, improving experimental accuracy.

Conclusions:

• The wave mixing method with S0 Lamb waves is a feasible and effective technique for early-stage fatigue damage evaluation.
• The sum combinational harmonic is a more reliable indicator of progressive fatigue damage.
• The phase reversal approach substantially enhances the quality and reliability of experimental results in fatigue damage assessment.