Non-destructive testing (NDT) is a material evaluation technique for ensuring its quality, safety, and dependability without causing any damage to it. Eddy current (EC) testing is a commonly used NDT method for identifying faults in electrically conducting specimens using conventional or printed circuit board (PCB) based probes. Due to its limited current carrying capacity, PCB based probes are less sensitive compared to conventional ones, while design and fabrication of later is time consuming and expensive.

In this study, we investigate a low-cost alternative method for building EC probes that may also be used to create planar and tubular array probes with ampacity comparable to that of conventional EC probes. A compact and machine-wound chip inductor was selected to be used as EC probe due to its wide working frequency range, minimal parasitics and reduced mutual inductance due to the presence of ferrite shield. Study of the electrical behaviour of chip inductor was performed using finite element method (FEM) based numerical simulations and results suggested that shielded chip inductor could be used for designing low profile EC probes. An array of chip inductors (20.5x15 mm2) was built on a flexible PCB and its performance was experimentally verified on planar aluminium sample (400  100  10 mm3) with a surface defect of width 2 mm and varying depth. For the probe kept directly over the defect, the maximum change in inductance observed was 1 Ω. The study further aims to experimentally validate the probe performance for planar and tubular samples with varying sizes of defects.

Keywords: chip inductor, eddy current, flexible array probe, non-destructive testing