Ultrasonic Flaw Echo Enhancement Based on Empirical Mode Decomposition.

Area of Science:

• Materials Science
• Mechanical Engineering
• Signal Processing

Background:

• Ultrasonic nondestructive testing (NDT) faces challenges in detecting flaw echoes due to backscattering and electronic noise.
• Distinguishing genuine flaw signals from noise is critical for accurate material integrity assessment.

Purpose of the Study:

• To propose and validate an Empirical Mode Decomposition (EMD) methodology for enhancing flaw echo detection in ultrasonic NDT.
• To improve the signal-to-noise ratio (SNR) and correlation of flaw echoes in noisy signals.

Main Methods:

• Decomposition of backscattered ultrasonic signals into intrinsic mode functions (IMFs) using EMD or ensemble EMD (EEMD).
• Selection of relevant IMFs based on sample entropy (SampEn) analysis.
• Application of Otsu's method for thresholding and windowing techniques to isolate flaw echoes for reconstruction.

Main Results:

• Significant enhancement of flaw echoes in both simulated and experimental ultrasonic signals.
• Achieved a 9.42 dB improvement in signal-to-noise ratio (SNR) for simulated signals.
• Improved the modified correlation coefficient (MCC) by 0.0099 for simulated signals, demonstrating enhanced signal fidelity.

Conclusions:

• The proposed EMD-based methodology effectively suppresses noise and enhances flaw echo detection in ultrasonic NDT.
• The technique shows practical applicability for processing experimental data from defects at varying depths.
• This approach offers a promising solution for improving the reliability and accuracy of ultrasonic inspection.