Numerical parametric study of Nonlinear Coda Wave Interferometry sensitivity to microcrack size in a multiple...

Area of Science:

• Materials Science
• Geophysics
• Nonlinear Acoustics

Background:

• Nonlinear Coda Wave Interferometry (NCWI) is a technique used to detect material damage.
• Heterogeneous materials with microcracked zones present challenges for damage assessment.
• Understanding the sensitivity of NCWI to micro-damage is crucial for its application.

Purpose of the Study:

• To numerically investigate the sensitivity and applicability of NCWI in heterogeneous materials with localized microcracks.
• To model the effect of a strong pump wave on crack length and its influence on ultrasonic coda waves.
• To establish a parametric sensitivity study of CWI observables concerning crack length variations.

Main Methods:

• Numerical simulations using the 2D spectral element method (SEM2D).
• Modeling the influence of a strong pump wave as an average increase in crack length.
• Quantifying changes in coda-type signals using coda wave interferometry (CWI).

Main Results:

• Signal stretching (relative velocity variation) showed a linear proportionality to global crack length change.
• Remnant decorrelation coefficient exhibited a quadratic proportionality to crack length change.
• NCWI demonstrated relevance for detecting varying damaged states in complex solids.

Conclusions:

• NCWI is a sensitive and applicable method for detecting micro-damage in heterogeneous materials.
• The established relationships provide a basis for quantitative nondestructive evaluation using nonlinear ultrasound.
• The findings are significant for assessing micro-damage levels in materials using nonlinear ultrasonic signals.