Mode extraction technique for guided waves in a pipe

Guided waves propagating in a pipe consist of many modes with different velocities and dispersions. To analyze these complex guided waves through a normal mode expansion technique, that is the fundamental theory on guided waves, we must first extract guided wave modes from received signals. In this study, we develop a mode extraction technique in which many received signals at different circumferential positions can be processed based on the fact that guided wave modes have different displacement distributions in the circumferential direction. After discussing the relevant theory, we verify our mode extraction technique experimentally using eight signals at eight different circumferential positions. Moreover, we show that the circumferential position of an excitation transducer, as well as the distance between an excitation transducer and a receiver in a pitch-catch configuration can be identified using the mode extraction technique. © 2005 Taylor & Francis Ltd.This is an Accepted Manuscript of an article published by Taylor & Francis in Nondestructive Testing and Evaluation on 19 Aug 2006, available at http://wwww.tandfonline.com/10.1080/10589750500062771

Defect imaging with guided waves in a pipe

Takahiro Hayashi and Morimasa Murase. Defect imaging with guided waves in a pipe. Journal of the Acoustical Society of America, 2005, 117(4), 2134. https://doi.org/10.1121/1.1862572

Defect imaging with guided waves propagating in a long range

Takahiro HAYASHI, Masahiro NAGAO, Morimasa MURASE, Defect imaging with guided waves propagating in a long range, Journal of Solid Mechanics and Materials Engineering, 2008, 2(7), pp. 888-899, https://doi.org/10.1299/jmmp.2.888

Rapid thickness measurements using guided waves from a scanning laser source

Takahiro Hayashia, Morimasa Murase and Muhammad Nor Salim. Rapid thickness measurements using guided waves from a scanning laser source. Journal of the Acoustical Society of America, 2009, 126(3), 1101. https://doi.org/10.1121/1.3177268

Imaging defects in a plate with full non-contact scanning laser source technique

Takahiro Hayashi, Morimasa Murase, Natsuki Ogura, Tsunaji Kitayama, Imaging Defects in a Plate with Full Non-Contact Scanning Laser Source Technique, MATERIALS TRANSACTIONS, 2014, 55(7), pp. 1045-1050, https://doi.org/10.2320/matertrans.I-M2014817

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