Nondestructive Evaluation (NDE) Technology Initiative Program (NTIP). Delivery Order 0033: Magnetostrictive Shear Guided Wave Sensor Technology for Bond Line Monitoring

Abstract : The magnetostrictive sensor (MsS) consists of a 0.005-0.010-inch-thick nickel strip bonded to the aircraft structure and activated with an excitation coil to generate an ultrasonic guided wave in the structure. The MsS is fixed to the surface and can remain on the surface for many years, thus, allowing data to be collected periodically to be carefully compared to a reference data so small changes in the structure can easily be detected. During this project, SwRI studied temperature and stress effects on the MsS bonded with various adhesives to various materials, evaluated the MsS for a number of geometries, and developed a model to help characterize the reflected guided waves from various types of defects. Data acquisition and analysis software was demonstrated and the MsS was optimized. The results obtained showed that the MsS bonded onto aluminum structure with 3M(TM)467 adhesive can be used over a temperature range of -65 F to 150 F to detect 1/4 inch by 1/4 inch edge delaminations in adhesively bonded patches, changes in crack growth of approximately 0.1 inch in defects under the patch, and defects such as cracks and corrosion as small as 0.03 inch by 0.03 inch under fasteners.