Flexible Array Probe with In-plane Differential Multi-Channels for Inspection of Micro-defects on Curved Surface

It is critical for maintaining safe operation of turbine blades to inspect the potential structural damages promptly. However, the industry still lacks for efficient tools for inspection of the curved surface. In this respect, a new flexible probe with in-plane differential coils is proposed. With the sophisticated configuration, the probe has four channels, which complement each other in terms of sensitivity to defects of different orientations. The in-plane differential scheme nulls the background signal and reduces the noise resulting in high sensitivity to micro-defects. The probe can be bended according to the curved surface due to its flexible configuration. A 3D finite element method model based on cluster parallel computation is utilized to study the feasibility and performance of the probe, and a prototype probe is developed and tested by scanning defects on the curved surface of a turbine blade sample. Further, a data fusion method is proposed to obtain better SNR so that defects with length*width*depth=2.5 mm*0.1 mm*0.1 mm can be identified. Based on repeated experiments, it is observed that the probability of detection with the fusion of the multi-channels is higher than that of each single channel demonstrating that the data fusion increases the reliability of the inspection.