Influence of metallic shields on pulsed eddy current sensor for ferromagnetic materials defect detection

• Influence of magnetic shield on PEC sensor for defects detectability was investigated.
• Relative sensitivity was used to estimate the defect detection performance.
• Aluminium shield can enhance amplitude of PEC response, but sensitivity is decreased.
• Iron shield has better shielding performance due to suppression of excited magnetic field.
• Iron shield can effectively improve sensitivity for both surface and subsurface defects in ferromagnetic materials.

Pulsed eddy current (PEC) with transient analysis is a significant advance over conventional eddy current testing using impedance analysis at a particular frequency. The fabrication and optimization of PEC sensor are important issues in PEC applications in nondestructive testing (NDT) field especially for ferromagnetic materials. In this work, the influence of metallic shields on circular PEC sensor for defect detectability in ferromagnetic metals has been investigated through finite element models (FEM) and experimental studies by comparing iron and aluminum shields with no-shield. Both simulations and experiments indicate that PEC probe with an aluminium shield can effectively enhance the amplitude of PEC response in both surface and subsurface defect detection. However, the sensitivity is decreased. In contrast, iron shield has better shielded performance and can effectively improve the sensitivity of both surface and subsurface defects detection in ferromagnetic materials.