Transient eddy current oscillations method for the inspection of thickness change in stainless steel

Detection and evaluation of corrosion and defects in industrial structures are extremely important for accident reduction and product quality assurance. We propose a new nondestructive testing (NDT) method called transient eddy current oscillations (TECO) to detect a change in thickness of stainless steel. This method uses a charged capacitor to discharge through an induction coil (excitation coil) and the resultant magnetic field detected by using a Hall-effect sensor, which is placed inside the cylindrical excitation coil at the bottom side axial center. Homogeneous stainless steel test specimen of different thicknesses has been prepared to test the feasibility of the TECO method. Three different features were identified in the detected magnetic field signal: envelope (peak amplitudes), zero crossing difference and the energy. Experimental results show a good correlation between detected features and the thickness of the test material. To verify the experimental results, simulations were performed using a commercial finite element modeling software. Results suggest that the proposed method can be a potential NDT tool for the detection of corrosion and wall thickness in industrial structures.