A new rosette-like eddy current array sensor with high sensitivity for fatigue defect around bolt hole in SHM

Boosting the sensitivity of eddy current sensors is one of the challenges of non-destructive testing to improve structure health monitoring. Rosette-like eddy current sensors have the best application prospect in structure health monitoring to detect fatigue-induced defects around a bolt hole. To boost the sensitivity of this kind of sensor, a new rosette-like eddy current array sensor is proposed. Same-direction exciting currents are used to make the eddy current distribution more sensitive to detect defect propagation. Moreover, a new layout of pickup coils and a graph algorithm are proposed to improve the sensor's angular resolution. Through finite element simulation and experimental tests, the eddy current distribution and the output signal during defect propagation of a traditional sensor and a new one are compared. Results show that the proposed sensor has higher sensitivity in detecting defect propagation than the traditional one.