MONITORING OF FATIGUE CRACKS USING PERMANENTLY-MOUNTED CONFORMABLE EDDY-CURRENT SENSORS

摘要

Eddy-current testing is a sensitive technique used for the detection of surface-breaking cracks in electrically-conductive structures. Eddy-current probes typically consist of one or two cylindrical coils of rectangular cross-section which carry an alternating current to induce eddy currents in the metallic structure being inspected. As the probe is scanned across the inspection surface, a surface-breaking flaw near the probe will interrupt the flow of eddy currents in the material, which is detected as a change in impedance of the probe. To enable eddy-current probes to be permanently mounted onto a complex structure to monitor crack growth in regions of high stress concentration it is useful if the probes are thin and conformable. Spiral coils fabricated using flexible printed circuit board technology satisfy these criteria and have the potential to provide either continuous or periodic structural health monitoring by tracking the variation in impedance of the spiral coils attached to the structure's surface.