Abstract: Material condition monitoring may be performed by electromagnetic sensors and sensor arrays mounted to the material surface. The sensors typically have a periodic winding or electrode structure that creates a periodic sensing field when driven by an electrical signal. The sensors can be thin and flexible so that they conform to the surface of the test material. They can also be mounted such that they do not significantly modify the environmental exposure conditions for the test material, such as by creating stand-off gaps between the sensor and material surface or by perforating the sensor substrate.

Abstract: An apparatus and a method of detecting wide spread fatigue damage (WFD) on aircraft using the absolute conductivity of the metal. A meandering winding magnetometer (MWM) having a plurality of parallel spaced linear conductor elements are placed in proximity to the aircraft. An electromagnetic field is imposed on the aircraft and the resulting response is sensed. The response is transformed to determine the conductivity of the aircraft structure. The mapping of the conductivity of the aircraft structure produces an indication where microcracks are located in the structure. These early indications of the density, spatial distribution and spatial orientation, as well as the size, of the microcracks give the user an indication of WFD.