Guided wave damage detection tomography for structural health monitoring in critical zones of pipelines

Structural health monitoring is becoming an increasingly important field across the globe as the amount of infrastructure increases and as preexisting structures deteriorate. A significant portion of this infrastructure is represented by oil and gas pipelines that are often exposed to harsh conditions causing corrosion and abrasive wear. Ultrasonic bulk wave measurement of critical zones in steel pipe implemented by conventional means has proven to be time consuming and dangerous to personnel, as high pressure lines can rupture upon testing due to degradation, causing injury to inspectors. Permanently placed ultrasonic transducers mounted around a critical zone on a pipeline can monitor wall thinning and other damage conditions safely and quickly via ultrasonic tomographic reconstruction of the pipeline structure. In this work, as an example, 16 small piezoelectric disks are attached to a 100 mm schedule 40 steel pipe elbow. Signals are excited and collected from each transducer in the array before and after each of several stages of damage introduction. A signal-difference coefficient comparing the collected signals with baseline data is implemented to tomographically reconstruct the region of interest and map any occurring damage. This experiment is successful in detecting a wide range of damage and demonstrates good discontinuity sizing and positioning.