Optimisation of pulsed eddy current probe for detection of sub-surface defects in stainless steel plates

• FEM based design optimisation of pulsed eddy current probe.
• Send-receive type ferrite cored probe shows better detection sensitivity.
• Experimental study also confirms its detection sensitivity for sub-surface defects.

Pulsed eddy current (PEC) technique is used for the detection of sub-surface defects in electrically conducting materials. In order to extend the application of PEC technique for the detection of defects in thick non-magnetic materials, the detection sensitivity of the probe need to be enhanced. Detection sensitivity of the probe mainly depends on the probe configuration. In view of this, optimisation of probe configuration for deeper penetration of magnetic field in the material is carried out through finite element modelling. Present study focuses on model based design optimisation of PEC probe for the detection of sub-surface defects located more than 4 mm from surface in a 8 mm thick AISI type 316 stainless steel plate. The performance of ferrite cored absolute probe, ferrite cored send-receive probe and ferrite cored send-receive probe with outer shielding has been compared and optimised probe has been fabricated. The detection sensitivity of the optimised probe has been studied using machined notches introduced at different depths.