Flexible array rotating eddy current detection for cracks at edge of holes

In order to solve the detection problem of crack at the edge of tiny cooling holes in turbine blades with complex profiles, a novel flexible array rotating eddy current probe was designed and fabricated in this paper. A modulated rotating eddy current array detection system was built, and a defect identification method based on the phase information of the array modulated rotating eddy current detection signal was proposed. The excitation part of the novel flexible array rotating eddy current probe adopted double-layer parallel circuit coil configuration and was designed and fabricated using flexible circuit board printing technology. This configuration can create a uniform eddy current field and reduce the coil area, facilitating the flexibility and miniaturization of the detection probe. Based on the array modulation rotating eddy current detection signal, a Lissajous and polar coordinate analysis diagram of the array cooling holes was established to judge the information of inner wall cracks at the edge of cooling hole based on the phase information in the Lissajous analysis diagram and the amplitude information in the polar coordinate analysis diagram. The effectiveness of the proposed novel flexible array rotating eddy current probe and the defect identification method for inner wall cracks was validated through numerical calculations and experiments.