Optimization Design of Rosette Eddy Current Sensor for Aircraft Structural Health Monitoring

To monitor the crack damage located at a bolt hole of metallic bolted-joint structure, based on the previous work of Goldfine, the paper proposes a type of rosette eddy current sensor and its structural geometry is optimized based on constructed semi-analytic forward equivalent model. Monitoring experiment of 2A12-T4 aluminum alloy under constant loading spectrum is carried out to validate the quantitative crack-monitoring capability of the optimized rosette eddy sensor. Model simulation results show that optimization winding widths are existed at specific space between sensing winding. The result of fatigue crack monitoring experiment of 2A12-T4 aluminum alloy under constant loading spectrum indicates that after the optimization design of driving frequency and sensor geometry structure, the first channel of the sensor is capable of monitoring on accumulated damage and the other three channels are capable of quantitatively monitoring on fatigue crack, with monitoring precision of 1 mm. The proposed rosette eddy current sensor achieves the whole lift cycle monitoring of specimen from accumulated damage to fatigue crack propagation, and shows a great promise for structural health monitoring of aircraft metallic bolt-joint structure.