Progress in Evaluation of Deep Artificial Defects from Sweep-Frequency Eddy-Current Testing Signals.

Area of Science:

• Materials Science
• Non-Destructive Testing
• Electromagnetism

Background:

• Austenitic materials are crucial in various industries but susceptible to defects.
• Detecting deep defects in thick materials non-destructively presents significant challenges.
• Traditional eddy current methods may struggle with deep or complex defect geometries.

Purpose of the Study:

• To apply and evaluate the sweep-frequency eddy current method for non-destructive investigation of deep artificial defects in thick austenitic materials.
• To assess the efficacy of an innovative eddy current probe with separate excitation and detection circuits.
• To explore the method's potential for defect characterization and input for machine learning models.

Main Methods:

• Utilized sweep-frequency eddy current testing with harmonic excitation.
• Investigated electric-discharge machined notches of defined geometry in 30 mm thick plates.
• Employed an innovative eddy current probe featuring separate excitation and detection circuits.
• Applied low-frequency excitation signals in conjunction with frequency sweeping.

Main Results:

• Successfully detected artificial defects up to 24 ± 0.5 mm deep in thick austenitic material.
• Demonstrated the robustness and potential of the sweep-frequency eddy current method for deep defects.
• Confirmed reliable defect detection even when the probe was not positioned directly above the defect.
• Achieved significant results using a specific probe configuration (fifth probe) and frequency sweeping.

Conclusions:

• The sweep-frequency eddy current method is a robust and effective technique for non-destructive evaluation of deep defects in thick austenitic materials.
• The innovative probe design and low-frequency excitation enhance the detection capabilities for challenging defect scenarios.
• The study provides valuable data for developing predictive models for real-world defects like fatigue and stress-corrosion cracks.