Research on internal defect detection of multilayer media based on phase coherence far-focused pixel-based imaging...

Area of Science:

• Non-destructive testing
• Ultrasonic imaging
• Materials science

Background:

• Traditional amplitude-based ultrasonic imaging struggles with low signal-to-noise ratio (SNR) and inconsistent characterization of internal defects in multilayer media.
• Challenges include interface reflections and material attenuation, particularly affecting identically sized flaws at varying depths.
• Existing methods often fail to accurately detect and quantify deep-seated defects.

Purpose of the Study:

• To introduce a novel phase-coherent far-focused pixel-based (PC-FPB) imaging algorithm.
• To address the limitations of traditional methods in ultrasonic inspection of multilayer structures.
• To enhance the detection and characterization of internal defects, especially those at greater depths.

Main Methods:

• Development of the PC-FPB imaging algorithm utilizing a vector coherence factor.
• Implementation of a novel scan-line-based coherence modulation strategy.
• Application of a dynamic threshold via multiplicative fusion to enhance defect signals and suppress noise.

Main Results:

• Significant enhancement in imaging intensity and SNR for deep-seated defects.
• Improved defect amplitude by 9.8 dB and image SNR by 7.7 dB in single-hole imaging.
• High consistency in imaging identically sized defects at varying depths, with a maximum quantification error of 0.245 mm² for 1 mm diameter defects.
• Average SNR increase of 15 dB and average lateral resolution improvement of 53.4% for defects at various depths.

Conclusions:

• The PC-FPB imaging algorithm effectively overcomes limitations of conventional amplitude-based methods.
• Demonstrated superior performance in detecting deep defects within multilayer structures.
• Confirms enhanced defect detection capabilities, improved SNR, and better lateral resolution.