Visualization analysis of internal defects in coatings based on terahertz imaging technology

Area of Science:

• Materials Science
• Non-Destructive Testing
• Optics and Photonics

Background:

• Non-metallic coatings are crucial in various industries, and their internal defects can compromise performance.
• Traditional non-destructive testing (NDT) methods may have limitations in detecting subtle defects within coatings.
• Terahertz (THz) waves offer unique penetration capabilities for non-metallic materials, showing potential for NDT.

Purpose of the Study:

• To develop and validate an integrated framework for characterizing defects in epoxy resin coatings using THz time-domain spectroscopy.
• To evaluate the effectiveness of super-resolution (SR) image reconstruction in enhancing the precision of defect analysis.
• To establish a high-precision NDT method for industrial coating inspection.

Main Methods:

• Utilized a THz time-domain spectroscopy system for transmission-mode detection.
• Developed a time-domain transmission model to identify internal defects and assess thickness detection limits.
• Integrated THz imaging with super-resolution (SR) reconstruction for high-precision defect visualization and quantification.

Main Results:

• Defect thickness detection error decreased below 8.5% for thicknesses above 0.6 mm.
• SR reconstruction significantly reduced area and volume estimation errors for defects thicker than 0.3 mm.
• For defects > 0.5 mm, SR-enhanced area estimation error was < 6% (min 0.99%), and volume error was minimized to 13.77%.

Conclusions:

• The combined SR reconstruction and THz imaging approach enables accurate segmentation, localization, and quantification of internal coating defects.
• This innovative framework enhances the assessment of coating uniformity and defect characterization accuracy.
• The study advances the application of THz imaging in industrial coating inspection, promoting more intelligent NDT technologies.