Surface mounted and scanning periodic field eddy-current sensors for structural health monitoring

Many aircraft components originally designed to last the design life of the aircraft without experiencing cracking (i.e., safe-life components) are now failing in service due to multiple site damage in locations not considered critical in original fatigue evaluations. For safe-life components that must now be managed by damage tolerance methods, periodic inspections are generally far more costly than for components originally designed with planned inspections. Often, the high cost of these inspections is associated with disassembly and surface preparation. This paper describes (1) surface mountable eddy-current sensors for periodic or continuous monitoring of difficult-to-access locations (e.g., in fuel tanks); (2) high resolution scanning eddy-current sensor arrays for imaging of subsurface cracks and corrosion using inductive sensing elements; and (3) a new giant magnetoresistive sensor with a shaped field drive winding for sensitivity to deeply buried flaws in aircraft structures.