Ultrasonic Guided Waves for Monitoring Underwater Corrosion

Abstract

This thesis reports the investigation of corrosion and its progression in plate specimen simulating ship hulls in uncoated and paint coated states using ultrasonic guided waves .The effectiveness of guided waves technique for corrosion monitoring in various states of ship hull structure (as in actual conditions in ships) has been studied. Current work proposes to use immersion transducers to generate guided elastic waves in plate geometries in first healthy state. Then guided waves are generated in steel plates undergoing corrosion damages. The signals in pitch catch orientation are send and received at particular critical angles. The variation in the signal received should lead to identify, locate and evaluate corrosion damage and determine the residual life of the structure. However, several key technologies must be established before the guided waves could be utilized in the monitoring of health of marine structures, a reliable technique for prediction of propagation of waves through submerged damaged specimens taking into account the fluid structure interaction must be established; a number of steel plates structures in uncoated and paint coated with and without initial scratch or damage conditions must be investigated and extend of corrosion be characterized to facilitate on site application of the developed methodology. The methodology is successfully to plates undergoing corrosion in marine environment. This thesis reports a non-contact, in-situ and non-destructive corrosion monitoring methodology for submerged plates using ultrasonic guided waves. Specific surface sensitive and core sensitive guided wave modes are utilized for monitoring plates undergoing accelerated impressed current corrosion in the presence of chlorides.