Development of Eddy Current Probe for Detection of Deep Sub-Surface Defects

ABSTRACT

Studies on design optimisation of eddy current probe have been carried out for detection of deep sub-surface defects in thick stainless steel plates. The performance of send–receive type air core, ferrite core, ferrite core with outer shielding, and cup-core probes has been analysed and compared using finite element modelling. The model predicted results have indicated that the cup-core probe ensures better sensitivity for detection of deep sub-surface defects. For experimental studies, a high sensitive eddy current instrument with digital lock-in amplifier functionality implemented in LabVIEW software has been developed. Experimental results have confirmed that cup-core probe is capable of detecting defects located at 8.0 mm below the surface in 12.0 mm thick stainless steel plates as well as simulated sub-surface localised corrosions. A linear relationship between phase angle and defect depth below the surface has been observed, apart from discrimination of sub-surface and surface defects.

KEYWORDS:

• Cup-core probe
• Digital lock-in amplifier
• Eddy currents
• Finite element modelling
• Stainless steel
• Sub-surface defects

Acknowledgments

Authors thank Dr T. Jayakumar, former director, Metallurgy and Materials Group, IGCAR Kalpakkam for many useful suggestions. Authors thank Mr V Arjun, Scientific Officer and Mr K. Samba Siva Rao, Senior Research Fellow from Non-destructive Evaluation Division, IGCAR, Kalpakkam for many useful technical discussions and for their help in the measurements.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Anil Kumar Soni

Anil Kumar Soni obtained his M.Tech in digital communication engineering. He is pursuing his doctoral degree in engineering science at HBNI, Mumbai. His thesis focuses on the development of the eddy current instrument and sensors for sub-surface defect detection using Eddy current testing.

E-mail: [email protected]; [email protected]

B. Sasi

B. Sasi has been working at IGCAR, Kalpakkam. Her areas of research include electromagnetic NDE, signal processing, image processing, sensor design and material characterization.

E-mail: [email protected]

S. Thirunavukkarasu

S. Thirunavukkarasu has been working at IGCAR, Kalpakkam. His area of research includes finite element modelling in electromagnetic NDE, signal processing and sensor design.

E-mail: [email protected]

B. Purna Chandra Rao

B. Purna Chandra Rao heading NDE Division and Robotics & Remote Handling Section, IGCAR, Kalpakkam, India. He is specialized in the areas of NDE of metallic materials for the detection and characterization of defects and microstructure.

E-mail: [email protected]