SBIR Phase I:Eddy Current Condition Monitoring of Metallic Flaws Under Surface Coatings Using GMR Sensors

This Small Business Innovation Research Phase I project proposes to use giant magnetoresistance (GMR) magnetic sensors and eddy current techniques to detect flaws in metallic components under insulative coatings. Innovations and improvements in surface treatments such as coatings and sprayings including thermal barrier coatings are useless unless degradation, wear, corrosion and oxidization due to thermal and mechanical stresses can be monitored under these surface treatments. Conditional monitoring using GMR sensors has the following advantages: (1) Refinement of present sensor technology will enable the manufacture of eddy current sensors of very high sensitivity thereby increasing the permissible lift-off. (2) Unlike ultrasonic methods, magnetic fields are not significantly affected by the presence of electrical insulating coatings. (3) The directional sensitivity of GMR based sensors allows detection of flaws near edges where cracks are more likely to initiate. This project will prove the feasibility of using GMR sensors and eddy current techniques to detect flaws under coatings. High sensitivity GMR sensors will allow the design of small, easily maneuvered, portable NDE units which can be used for structure monitoring, surveillance, critical component monitoring and equipment preparedness.