Analysis of Tilt Effect on Notch Depth Profiling Using Thin-Skin Regime of Driver-Pickup Eddy-Current Sensor

Area of Science:

• Materials Science
• Electromagnetism
• Non-Destructive Testing

Background:

• Electromagnetic eddy current sensors are vital for detecting surface flaws in metals.
• Sensor tilt introduces significant errors in depth profiling, limiting accurate flaw characterization.
• Existing methods struggle to compensate for unintentional sensor inclination during measurements.

Purpose of the Study:

• To develop a revised analytical algorithm for tilted driver-pickup eddy current sensors.
• To improve the accuracy of depth profiling for surface notches under varying sensor tilt angles.
• To validate the algorithm's effectiveness through experimental measurements.

Main Methods:

• Developed a revised analytical algorithm based on the eddy current thin-skin regime for a tilted transmitter-receiver (T-R) sensor.
• Designed a bespoke T-R sensor with a 1 mm mean radius for high-resolution measurements.
• Conducted experiments on an aluminum sheet with machined notches using the T-R sensor at various tilt angles and scanning resolutions (0.25 mm).

Main Results:

• The proposed algorithm significantly reduces the impact of sensor tilt on notch depth profiling.
• Experimental results show that notch depths can be retrieved with a deviation of less than 10% for tilt angles up to 60 degrees.
• The real and imaginary parts of the measured voltage were fitted with the analytical algorithm for accurate depth retrieval.

Conclusions:

• The revised algorithm enables accurate depth profiling of metal surface notches using tilted eddy current sensors.
• This method enhances the reliability of non-destructive testing by mitigating errors caused by sensor inclination.
• The findings are crucial for improving the quantitative assessment of surface defects in metallic components.