ANALYSIS OF GUIDED WAVE PROPAGATION BY VISUALIZING IN-PLANE AND OUT-OF-PLANE MODES

Abstract

Guided wave techniques in nondestructive evaluation provide practical application for a long range of pipe inspection. On the contrary, the phenomenon of mode conversions around defects are not been explained experimentally, and visualization of guided wave propagation is significantly useful to describe behavior of mode conversions around defects from the measured RF signals in a pipe. This paper presents visualization of guided waves around defects in a pipe using many waveforms detected by Laser Doppler Vibrometer (LDV) scanning equipped with a robot arm. These waveforms were detected at many points on a surface of a pipe from two different directions. As result of the measurements, incident wave and reflected wave of the in‐plane and out‐of‐plane vibrations can be separated in the visualization results. The images clearly visualize the reflected waves from a circumferential notch and an oblique stretching notch that strongly indicate the existence of mode conversions around defects.