Study on Novel Transformer Model of Eddy Current Testing and Signal Decoupling of Thermal Barrier Coating

doi:10.3901/JME.2025.12.012

Abstract

Abstract: Thermal barrier coating(TBC) consists of a ceramic coating(TC), a bonding coating(BC), and a substrate. Thickness measurement of TBC plays an important and urgently needed role in quality control of engine blades. TBC has the characteristics of complicated structure, uneven thickness, low conductivity and similar electromagnetic parameters. The resultant signals are weak and strongly coupled. Therefore, it is difficult to accurately detect the coating thickness. A novel three-winding transformer model of eddy current(EC) is established, and the research is conducted on the signal coupling physics and a new method for thickness measurement. Firstly, the attenuation and diffusion characteristics of ECs in each layer of TBC are explored. The equivalent EC ring is introduced, and the parameters are determined through field-circuit transformation and energy equivalent to establish a three-winding transformer model. Secondly, the signal coupling mechanism between TC and BC is explored. The characteristic signals of the thicknesses of TC and BC, are obtained by feature matching, frequency regulation, and discrete decomposition of EC ring, to decouple the thickness signals. Finally, an EC prototype is developed to economically achieve simultaneous and accurate thickness measurements of TC and BC. The results show that the relative errors of TC and BC are less than 5% and 10.3%, respectively.

Key words: thermal barrier coating, eddy current, coupling mechanism, novel transformer model, thickness detecting system

CLC Number:

TG156

LI Chao, FAN Mengbao, CAO Binghua, SUN Fengshan, YE Bo, YAN Jiahang. Study on Novel Transformer Model of Eddy Current Testing and Signal Decoupling of Thermal Barrier Coating[J]. Journal of Mechanical Engineering, 2025, 61(12): 12-25.

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