Wireless ultrasonic guided wave tomography for corrosion monitoring

Structural Integrity of predetermined critical zones in a structure is of growing interest in the non-destructive testing (NDT) and structural health monitoring (SHM) communities. Quite often the presence of defects does not imply the end of life of the underlying structure and it could be economical to continue using the structure until the damage severity reaches a point where it can no longer be used. For structures like pipelines and aircraft in which a failure can be catastrophic, it is extremely important to monitor continuously any defects on the structure. Leave in place sensors provide a convenient way to embed the sensors permanently on the structure to monitor periodically and to establish its integrity. Wireless sensing units provide a robust means to regularly monitor a structure and return the data to a central data collection infrastructure. In this study we explore the design of a wireless tomographic imaging system that uses Lamb wave propagation characteristics on a structure to map accurately the material loss zones due to corrosion in the area enclosed by the sensors. The wireless unit has an actuator to excite the piezoceramic sensors and the computational capability to interrogate the signals in real time and to communicate the information. The capability of the system is illustrated by testing it on an aluminum plate with simulated corrosion damage and the results are presented.