Ultrasonic Classification of Defects in Thin-walled Structures

This thesis focused on the development of techniques to detect and estimate the size of circular corrosion defects in thin-walled structures using ultrasonic guided waves. A 3D Finite Element (FE) model was developed to simulate the propagation of waves in thin-walled plates. The model was validated with experimental analysis using an Electro-Magnetic Acoustic Transducer (EMAT). Using a combination of fundamental and higher order horizontally polarized shear waves, the loss in amplitude of the received waves could be correlated to the minimum diameter of a defect. The transmitted pulse was delayed by an amount correlated to minimum defect diameter at the bottom of the defect. The 3D FE model predicted the received signals in plates with defects with an average error of 5%Âą2% for amplitude changes and 19%Âą17% for pulse delays. These results suggest that a 3D model can be used to predict the effects of defects on shear wave propagation.M.A.S