Experimental Investigation of Eddy Current Pulsed Thermography Based on Ferrite-Yoke–Helmholtz-Coil for the Inspection of Hidden Corrosion Defects in CFRP-Reinforced Steel Structures

Carbon fiber reinforced polymer has been widely used in the repair and reinforcement of steel structures due to its excellent structural performance. The CFRP-reinforced steel structures are widely used in various industries. However, due to the effect of various unexpected loads, hybrid structures are prone to generate defects, which will harm structure safety. Hidden corrosion defect on the interface of CFRP and steel substrate is a typical defect type and proposes an urgent need for non-destructive testing (NDT) methods. This study investigates the possibilities of corrosion defect detection using eddy current pulsed thermography (ECPT) and proposes an improved excitation coil configuration, ferrite-yoke-Helmholtz-coil, to improve the effectiveness and generality of the ECPT technology. Experiments were conducted on the CFRP-reinforced steel structure with prefabricated corrosion defects, and the results demonstrate the effectiveness of the proposed excitation configuration. The influence factors of the detection effect were also studied, including the defect size, excitation current, and excitation duration. The findings demonstrate that the proposed excitation coil configuration is efficient for hidden corrosion defect detection.