Visualization and modal analysis of guided waves from a defect in a pipe

Many commercial guided wave pipe inspection techniques use an axisymmetric torsional mode T(0, 1) as well as a longitudinally vibrating L(0, 2) mode as incident waves since the torsional mode has prominent characteristics of low attenuation and nondispersion. However, reflected waves from defects in a pipe contain many modes other than the incident torsional mode, and the complex reflected wave propagation sometimes prevents us from locating defects in the field. Therefore, we carried out a visualization of guided wave propagations around the full circumference of pipes to explain the behavior of reflected waves from defects that occur in pipe inspections. In this study, a large number of RF signal measurements at many locations on the curved surfaces of pipes were performed using a laser Doppler vibrometer (LDV) and a 6-axis robot arm that scanned over the curved surfaces of two pipes with circumferential and oblique defects. The visualizations of guided wave propagations from defects are shown for both in- and out-of-plane vibrations to analyze the mode conversions that occur in pipes around these defects when using the axisymmetric torsional mode T(0, 1) as an incident wave in pipe inspections. © 2009 The Japan Society of Applied Physics.Salim M., Hayashi T., Murase M., et al. Visualization and modal analysis of guided waves from a defect in a pipe. Japanese Journal of Applied Physics, 48(7S), 07GD06 (2009) https://doi.org/10.1143/JJAP.48.07GD06