Simulation Analysis of Pulsed Eddy Current Detection Signal of Thermal Barrier Coatings Thickness Measurement

A study is conducted on the detection signal utilized to measure the thickness of thermal barrier coatings (TBCs) with pulsed eddy current (PEC) technology. Via the definition of sensitivity of thermal barrier coatings thickness measurement, an analysis is conducted to determine the influence of the inside diameter, width, and height of the excitation and detection coil on sensitivity. To obtain the optimal parameters of the excitation and detection coil, the response surface method in the Design Expert software is utilized. In addition, an analysis is conducted to determine the influence of the lift-off effect on the pulsed eddy current detection signal of the thermal barrier coatings. In order to minimize the impact of the lift-off effect on the detection signal, a two-stage difference method was proposed as a preprocessing step. Through the simulation experiment, it is found that when inner diameter is increased, width is widened, and height is reduced, the sensitivity of thickness measurement is heightened accordingly, if the number of coil turns remain constant and the geometry parameters of the excitation and detection coil are constrained within a particular range. Besides, coil height has a more significant effect on sensitivity than other factors. Sensors optimized by the response surface method have higher sensitivity when measuring the thickness of thermal barrier coatings. The impact of the lift-off effect is significant on the detection signal, and the two-stage difference method can efficiently minimize the effect.