Keynote Speech

Tracking of Micro-damages by Nonlinear Guided Waves

by

Prof. Cho, Younho

President of Foreign Affairs Committee of South Korea Nnondestructive Testing Association

Head of Dept. Mechanical Systems Design, Pusan National University, Korea.

Continuous tracking of material micro-damages has been one of the most demanding technical needs for safety-critical structures. Due to the sensitivity of acoustic nonlinearity to micro-damages, the nonlinear ultrasonic technique has been explored as a promising tool for detection and tracking of micro-damages. In this talk, nonlinear feature of guided wave propagration in plate-like structures is firstly presented. The study shows that physically based feature selection is essential for efficient second harmonics generation of guided waves. The investigations of an experimental scheme for characterizing thermal fatigue damage in composite laminates using second harmonic Lamb waves are introduced secondly. Thirdly, accumulative thermal fatigue damage assessment in an isotropic pipe using nonlinear guided wave is discussed. To identify the nonlinear source and locate the nonlinear response, the feasiblity of nonlinear ultrasonic detection by collinear and non-collinear Lamb wave mixing techniques are also presented.