Defect Detection in Plated Structures Using Ultrasonic Guided Waves

Many structures like ship hulls, oil storage tanks, off shore oil platforms etc. are assemblies of large plate like components which are prone to deterioration and damages. These structures are subjected to damages in the form of environmental degradation, excessive loads, fatigue loads, corrosion, etc. If these changes go unnoticed at the initial stages, it may lead to catastrophic failure of the systems. This necessitates the development of an efficient monitoring technique of these plated structures in which the large areas can be scanned quickly. Guided ultrasonic waves which have stress distributed through thickness of the plate and can propagate over longer distances provide an effective solution in such cases. This study presents a non-destructive technique for damage detection in plates using guided ultrasonic waves. Plate specimens with a notch like defect geometries were tested with varying defect depths and location. Two ultrasonic testing techniques-pulse transmission and pulse echo were effectively used in the experiment. Time of flight (using phase velocity) measurement in pulse echo and amplitude attenuation measurement in pulse transmission were metrics of exact location and extent of damage in the specimens.