Visualization and Modal Analysis of Guided Waves from a Defect in a Pipe

概要

論文の詳細を見る
Many commercial guided wave pipe inspection techniques use an axisymmetric torsional mode $\mathrm{T}(0,1)$ as well as a longitudinally vibrating $\mathrm{L}(0,2)$ 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 $\mathrm{T}(0,1)$ as an incident wave in pipe inspections.
2009-07-25