A planar electromagnetic sensor for crack monitoring in large-opening structures

To address the need for crack monitoring in aircraft wing large-opening structures, this paper presents a novel planar electromagnetic sensor based on the principle of electromagnetic induction. The sensor's layout and structure are detailed. Using a finite element analysis model, the mechanism of crack monitoring is explored. When a crack emerges, it distorts the eddy current path in the conductive structure, alters the magnetic field around the sensor's induction channels, and causes variations in the voltage signals picked up by these channels, enabling effective crack assessment. Fatigue crack monitoring tests on large-opening structures confirm the sensor's feasibility. As cracks propagate to specific induction channels, the corresponding response signals intensify with crack growth until reaching a steady state. By identifying the inflection points in these signal variations, both the position and length of cracks can be accurately determined. Test results show that the sensor can detect cracks as small as 2 mm and quantitatively measure crack length with a precision of 2 mm.