Physics-guided and region adaptive fusion approach for decoupling measurement of thermal barrier coating thickness

Accurate characterization of Thermal Barrier Coating (TBC) thickness is crucial for ensuring the operational safety of aero-engine turbine blades. However, complex electromagnetic interactions create non-linear coupling effects between the top coating (TC) and bond coating (BC), making it extremely difficult to precisely decouple the TC and BC thicknesses. To address the non-linear coupling and sparse calibration challenges in eddy current testing (ECT) of TBCs, this paper proposes a physics-guided and region adaptive fusion (PG-RAF) decoupling method. First, a quadratic shape function model is introduced to eliminate geometric distortion by accurately mapping non-linear impedance curvature. Second, a physics-guided polynomial model incorporating electromagnetic attenuation laws is established to prevent numerical divergence in extrapolation regions. Third, a region adaptive fusion strategy dynamically adjusts model weights based on the measurement point’s location to optimize precision. Experimental results indicate that under standard calibration, the method reduces TC and BC measurement errors to 0.78% and 1.41%, respectively. Under non-uniformly distributed and sparse calibration, it effectively suppresses divergence, maintaining TC and BC error within 1.96% and 4.62%. This approach successfully balances high detection precision with engineering robustness.