The interaction of fundamental torsional guided waves from axial and oblique defects in pipes

2021 ◽  
Vol 63 (6) ◽  
pp. 334-340
Author(s):  
Young-Wann Kim ◽  
Kyung-Jo Park
Keyword(s):  
Reflection Coefficient ◽  
Crack Length ◽  
Guided Waves ◽  
Torsional Mode ◽  
Multimodal Signals ◽  
Mode Decomposition ◽  
Chirplet Transform ◽  
Axial Crack ◽  
Circumferential Extent ◽  
Oblique Crack

A quantitative study of the interaction of the T(0,1) torsional mode with axial and oblique defects in a pipe is presented in this paper. A mode decomposition technique employing the chirplet transform is used to separate the multimodal signals reflected from the defects. Reflection signals are obtained from experiments on a carbon steel pipe. The influence of the crack length and inclination angle on the reflection is investigated. The reflection from an axial defect is found to consist of a series of wave pulses with gradually decaying amplitude. The results show that the reflection coefficient of an axial crack initially increases with the crack length but finally reaches an oscillating regime. Furthermore, for an oblique crack, it is revealed that the reflection coefficient is linearly dependent on the equivalent circumferential extent of the defect and is independent of the axial length.

The Reflection of Guided Waves From Circumferential Notches in Pipes

1998 ◽  
Vol 65 (3) ◽  
pp. 635-641 ◽  
Author(s):  
D. N. Alleyne ◽  
M. J. S. Lowe ◽  
P. Cawley
Keyword(s):  
Finite Element ◽  
Reflection Coefficient ◽  
Elastic Wave ◽  
Linear Function ◽  
Laboratory Experiments ◽  
Guided Waves ◽  
Axially Symmetric ◽  
Reflection Function ◽  
General Applicability ◽  
Circumferential Extent

The reflection of the L(0, 2), axially symmetric guided elastic wave from notches in pipes is examined, using laboratory experiments and finite element simulations. The results show that the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the notch, and is a stronger function of the through thickness depth of the notch. The motivation for the work was the development of a technique for inspecting chemical plant pipework, but the study addresses the nature of the reflection function and has general applicability.

The variation of the reflection coefficient of extensional guided waves in pipes from defects as a function of defect depth, axial extent, circumferential extent and frequency

2002 ◽  
Vol 216 (11) ◽  
pp. 1131-1143 ◽  
Author(s):  
P Cawley ◽  
M J S Lowe ◽  
F Simonetti ◽  
C Chevalier ◽  
A G Roosenbrand
Keyword(s):  
Finite Element ◽  
Reflection Coefficient ◽  
High Frequency ◽  
Guided Waves ◽  
Three Dimensional ◽  
Element Analysis ◽  
Low Frequencies ◽  
Frequency Regime ◽  
Circumferential Extent ◽  
Part Thickness

The reflection coefficients of extensional guided modes from notches of different axial, circumferential and through-thickness extent in pipes of different diameters have been studied using finite element analysis. A selection of the predictions has also been validated by experiments. For part-thickness notches of a given circumferential extent and minimal axial extent, the reflection coefficient increases monotonically with depth at all frequencies, and increases with frequency at a given depth. When the wavelength is long compared to the pipe wall thickness, the reflection coefficient from part-thickness notches of a given circumferential extent is a strong function of the defect axial extent, the reflection being a maximum at an axial extent of about 25 per cent of the wavelength and a minimum at 0 and 50 per cent. The reflection coefficient is a linear function of the defect circumferential extent at higher frequencies (with frequency-diameter products greater than about 3000 kHz mm) where a ray theory analysis explains the behaviour, while at low frequencies the reflection coefficient at a given circumferential extent is reduced. In the high-frequency regime, the axial extent of a through-thickness defect has little influence on the reflection coefficient, while it is important at lower frequencies. Three-dimensional, finite element predictions in the high-frequency regime have shown that the reflection coefficient from a part-thickness, part-circumferential defect can be predicted by multiplying the reflection coefficient for an axisymmetric defect of the same depth and axial extent by that for a through-thickness defect of the same circumferential extent.

Theoretical and Experimental Investigation of Pipe Wall Thinning Detection Using Guided Waves

2008 ◽  
Author(s):  
Isoharu Nishiguchi ◽  
Fumitoshi Sakata ◽  
Seiichi Hamada
Keyword(s):  
Experimental Data ◽  
Power Generation ◽  
Experimental Investigation ◽  
Reflection Coefficient ◽  
Guided Waves ◽  
Pipe Wall ◽  
Thermal Power ◽  
Wall Thinning ◽  
Torsional Waves ◽  
Simplified Method

A method to investigate pipe wall thinning using guided waves has been developed for pipes in thermal power generation facilities. In this paper, the reflection coefficient and the transmission coefficient are derived for the torsional waves which propagate along a pipe and a simplified method to predict the waveform is proposed. The predictions of the waveforms by the FEM and a simplified method based on the reflection of torsional waves are also examined by comparing with experimental data.

Damage Imaging of Pipes in Nuclear Power Plants Using Torsional Guided Wave Modes

2013 ◽  
Vol 577-578 ◽  
pp. 661-664
Author(s):  
Zhao Xiang Wei ◽  
Hong Xu ◽  
Hong Yuan Li
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Power Plants ◽  
Guided Waves ◽  
Axial Position ◽  
Imaging Method ◽  
Long Distance ◽  
Torsional Mode ◽  
Damage Imaging

Ultrasonic guided waves can propagate a long distance in pipeline with little attenuation. This means the damage in nuclear power plant can be detected from a remote single position. In the paper, the propagation of the guided waves are analyzed for the nuclear power plant pipes, and the axisymmetric torsional mode T(0,1) is chosen as the detection mode. An imaging method based on the synthetic focusing algorithm is used to obtain the damage information. The method is then verified by the finite element model. Results illustrate that the damage can be detected and located accurately by the damage imaging method. Not only the axial position, but also the circumferential position can be located simultaneously.

Scattering of the fundamental torsional mode at an axial crack in a pipe

2010 ◽  
Vol 127 (2) ◽  
pp. 730-740 ◽  
Author(s):  
M. Ratassepp ◽  
S. Fletcher ◽  
M. J. S. Lowe
Keyword(s):  
Torsional Mode ◽  
Axial Crack

scholarly journals Guided Wave Inspection of Bars in Reinforced-Concrete Beams Using Surface-Mounted Vibration Sensors

Vibration ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 343-356
Author(s):  
Evelyne El Masri ◽  
Timothy Waters ◽  
Neil Ferguson
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Reflection Coefficient ◽  
Guided Waves ◽  
Transfer Functions ◽  
Concrete Beams ◽  
Guided Wave ◽  
Reinforced Concrete Beams ◽  
Invasive Technique ◽  
Reflection Coefficients

Steel reinforcement bars (rebars) in concrete structures are inaccessible and not conducive to many inspection methods. This paper proposes a non-invasive technique based on guided waves for detecting localised abnormalities in rebars embedded in concrete beams. The technique is predicated on previously published observations that guided waves are strongly reflected by discontinuities at the frequency at which they begin to propagate, i.e., at cut-on. The reflection coefficient at cut-on is estimated using a simple wave decomposition in which a near-zero wavenumber value is assumed. A simulated study is first carried out to evaluate the technique on a concrete beam featuring four rebars. The wave finite element approach is adopted to model two uniform beams which are coupled via a short, damaged section modelled in conventional finite element analysis. Estimated reflection coefficients arising from the discontinuity are close to the true values at cut-on and independent of frequency elsewhere, so that no prior knowledge of cut-on frequencies is required. Three steel-reinforced concrete beams were fabricated—one uniform and two with localised rebar damage—and reflection coefficients were estimated from measured transfer functions. As predicted, abrupt deviations in the reflection coefficient occurred at cut-on frequencies for both damaged beams.

PIPELINE INSPECTION USING A TORSIONAL GUIDED-WAVES INSPECTION SYSTEM. PART 1: DEFECT IDENTIFICATION

2014 ◽  
Vol 06 (04) ◽  
pp. 1450034 ◽  
Author(s):  
M. KHARRAT ◽  
M. N. ICHCHOU ◽  
O. BAREILLE ◽  
W. ZHOU
Keyword(s):  
Long Range ◽  
Guided Waves ◽  
Inspection System ◽  
Torsional Mode ◽  
Defect Identification ◽  
Pipeline Inspection ◽  
Fast Screening ◽  
System Part ◽  
The Hilbert Transform ◽  
Numerical Treatments

A steel pipeline of about 60 m long containing several pipes and structural singularities (bends, welds, clamps, etc.) is inspected in this work using a guided-waves technique. The inspection system is a pair of transducer-rings operating with the torsional mode T(0,1) and allows the long-range fast screening of the structure from defined measurement points. Recorded signals have submitted some numerical treatments in order to make them interpretable. The wavelet analysis is one of them and serves for denoising the raw signals. Besides, the Hilbert transform (HT) is applied in order to obtain the wave signals' envelopes leading to simplified curves easy to interpret. The processed signals are analyzed to identify defects' reflections from structural-singularities' echoes in the pipeline. The inspection system prove its efficiency for a global screening of such a long-range pipeline by detecting and localizing the defects.

A study on torsional guided wave EMAT array and its application in embedment depth inspection of guardrail post

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1065-1072
Author(s):  
Yinghong Zhang ◽  
Bin Wang ◽  
Xiao Wei ◽  
Zhenghua Qian
Keyword(s):  
Guided Waves ◽  
Permanent Magnets ◽  
Ultrasonic Transducer ◽  
Experimental System ◽  
Guided Wave ◽  
Embedment Depth ◽  
Torsional Mode ◽  
Working Principle ◽  
Different Depths ◽  
Set Up

It is always a challenge to quickly and effectively inspect the embedment depth of highway guardrail posts. This paper focuses on an electromagnetic ultrasonic transducer (EMAT) array that can excites torsional mode (T-mode) guided waves and applies it to check the embedment depth of guardrail posts. First of all, we presented a torsional guided wave EMAT array that can be used to quickly inspect the embedment depth of guardrail posts. The working principle of the EMAT array was described in detail. Secondly, a torsional guided wave EMAT array composed of 12 racetrack coils and 24 permanent magnets was simulated to verify the excitation and propagation process of torsional guided wave in a post. Then, a method for detecting the embedment depth of a post using the travel time of a torsional guided wave in the post was put forward. Finally, an experimental system was set up to carry out embedment depth detection experiments on posts with different depths buried in soil and concrete. Experiments have verified the feasibility of using the torsional guided wave EMAT array to inspect the embedment depth of the guardrail post.

A flexural mode guided wave transducer for pipes based on magnetostrictive effect

2020 ◽  
Vol 64 (1-4) ◽  
pp. 335-342
Author(s):  
Yun Sun ◽  
Jiang Xu ◽  
Chaoyue Hu ◽  
Guang Chen ◽  
Yunfei Li
Keyword(s):  
Magnetic Field ◽  
Guided Waves ◽  
Permanent Magnets ◽  
Wave Structure ◽  
Guided Wave ◽  
Circumferential Direction ◽  
Bias Magnetic Field ◽  
Flexural Mode ◽  
Axial Crack ◽  
Wave Transducer

The flexural mode guided waves of pipes which are sensitive the axial crack and suitable for wave focused gain more attention recently. In this paper, a non-contact flexural mode guided wave transducer based on magnetostrictive effect is provided for pipes. Based on the magnetostrictive transduction principle and the wave structure of the flexural mode guided wave, the sensing method for generating and receiving the flexural mode guided waves based on magnetostrictive effect is obtained. According to the theoretical analysis, a non-contact magnetostrictive transducer for F (3, m) mode guided waves is given. Six permanent magnets which are evenly distributed in the circumferential direction of the pipe and arranged in opposite polarities are employed to provide the bias magnetic field in the circumferential direction. A solenoid coil is employed to induce the axial alternating magnetic field. The bias magnetic field distribution of the flexural mode guided wave in the pipeline is analyzed by the finite element simulation. The mode of the transduction guided wave in the pipe is verified by experiments based on the dispersion curves.

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