Resonant frequency tracking mode on eddy current pulsed thermography non-destructive testing

Area of Science:

• Non-destructive testing
• Electromagnetic non-destructive evaluation
• Smart monitoring

Background:

• Eddy current pulsed thermography (ECPT) is a valuable non-destructive testing (NDT) method.
• Excitation source distortion in ECPT negatively impacts detection effectiveness.
• Resonant frequency distortion is a key challenge in ECPT excitation sources.

Purpose of the Study:

• To develop and validate a fast resonant frequency tracking loop for ECPT.
• To mitigate resonant frequency distortion in the excitation source.
• To improve defect detectability in ECPT through enhanced excitation.

Main Methods:

• Implementation of a fast resonant frequency tracking loop using Direct Digital Synthesizer (DDS) and all-digital phase-locked loop.
• Theoretical analysis and simulation of the tracking loop's working principle.
• Experimental validation using a manufactured prototype as an ECPT excitation source.

Main Results:

• The developed loop effectively tracks resonance frequency in real-time.
• The prototype excitation source eliminates the need for water-cooling and offers adjustable tracking speed.
• Reduced resonant frequency tracking time significantly improved defect detectability in steel and stainless steel samples.

Conclusions:

• The fast resonant frequency tracking loop is a promising solution for improving ECPT performance.
• The developed excitation source demonstrates practical application potential for advanced NDT.
• Optimizing tracking speed is crucial for enhancing crack detection capabilities in ECPT.