Split-Spectrum Signal Processing for Reduction of the Effect of Dispersive Wave Modes in Long-range Ultrasonic Testing

Pedram, Seyed Kamran; Haig, Alex; Lowe, Premesh Shehan; Thornicroft, Keith; Liu, Gan; Mudge, Peter

doi:10.1016/j.phpro.2015.08.106

Cited by 10 publications

(13 citation statements)

References 9 publications

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“…This value is the best possible compromise between the achieved defect length and the possibility of detecting false alarms. For method three, the average value is calculated using Equation (11), and minimum and maximum values are achieved by manually replacing the average in Equation (14). For both of the other methods, the average value is calculated manually from the achieved minimum and maximum values in the tests.…”

Section: Limits Definitionsmentioning

confidence: 99%

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Detection of Defects Using Spatial Variances of Guided-Wave Modes in Testing of Pipes

2018

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In the past decade, guided-wave testing has attracted the attention of the non-destructive testing industry for pipeline inspections. This technology enables the long-range assessment of pipelines’ integrity, which significantly reduces the expenditure of testing in terms of cost and time. Guided-wave testing collars consist of several linearly placed arrays of transducers around the circumference of the pipe, which are called rings, and can generate unidirectional axisymmetric elastic waves. The current propagation routine of the device generates a single time-domain signal by doing a phase-delayed summation of each array element. The segments where the energy of the signal is above the local noise region are reported as anomalies by the inspectors. Nonetheless, the main goal of guided-wave inspection is the detection of axisymmetric waves generated by the features within the pipes. In this paper, instead of processing a single signal obtained from the general propagation routine, we propose to process signals that are directly obtained from all of the array elements. We designed an axisymmetric wave detection algorithm, which is validated by laboratory trials on real-pipe data with two defects on different locations with varying cross-sectional area (CSA) sizes of 2% and 3% for the first defect, and 4% and 5% for the second defect. The results enabled the detection of defects with low signal-to-noise ratios (SNR), which were almost buried in the noise level. These results are reported with regard to the three different developed methods with varying excitation frequencies of 30 kHz, 34 kHz, and 37 kHz. The tests demonstrated the advantage of using the information received from all of the elements rather than a single signal.

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Section: Limits Definitionsmentioning

confidence: 99%

“…Another method for filtering the guided waves signal is the work of Pedram et al in Split-Spectrum Processing (SSP) [14,15], whereby through selecting the optimum filter parameters, the coherent noise of the test cases can be removed. However, automatic selection of the optimum filtering parameter is not possible at present.…”

Section: Introductionmentioning

confidence: 99%

Detection of Defects Using Spatial Variances of Guided-Wave Modes in Testing of Pipes

2018

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“…(such as ultrasonic signal propagation speed, amplitude, etc.) in ultrasonic testing for stress experiments [48][49] . Explore the methods for correcting errors through tentative experiments, once the testing object and experimental condition change, many experiments are needed to find the method to correct the error.…”

Section: The Influence Mechanism Of Macro Factors On Ultrasonic Testimentioning

confidence: 99%

“…Modern signal processing technology can improve the reliability and accuracy of stress testing result to a certain extent. [50][51] Fig.6 (a) and (b) are Rayleigh wave signal propagating in a fixed acoustic path in Fe314 laser cladding coating under 34MPa and 230MPa tensile stress respectively [52] . It can be seen from Fig.…”

Section: The Influence Mechanism Of Macro Factors On Ultrasonic Testimentioning

confidence: 99%

Progresses and Challenges of Ultrasonic Testing for Stress in Remanufacturing Laser Cladding Coating

Yan¹,

Dong²,

Xu³

et al. 2018

Preprint

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Stess in laser cladding coating is an important factor affecting the safe operation of remanufacturing components. Ultrasonic testing has become a hot direction in nondestructive evaluation of stress, because it has the advantages of safety, non-destructive and on-line detection. This paper provides a review of ultrasonic testing for stress in remanufacturing laser cladding coating. It summarizes the recent research outcomes on ultrasonic testing for stress, analyzes mechanism of ultrasonic testing for stress. Remanufacturing laser cladding coating shows typical anisotropic behaviors, the ultrasonic testing signal in laser cladding coating is influenced by many complex factors, such as microstructure, defect, temperature and surface roughness, etc. At present, ultrasonic testing for stress in laser cladding coating can only be done roughly. The paper discusses active mechanism of micro / macro factors to the reliability of stress measurement and the impact of stress measurement to the quality and safety of remanufacturing components. Base on the discussion, the paper proposes strategies for acquisition of nondestructive, rapid and accurate measurement of stress in remanufacturing laser cladding coating.

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“…On the other hand, other approaches have also been reported in the literature where narrowband sine waves were used as excitation sequence. Kamran et al investigated split-spectrum processing [13][14][15], where the time-domain signal is decomposed into multiple signals in different frequency bands, and then recombined in time-domain in order to remove the coherent noise. In their most recent work [15], it was reported that using the optimum filter parameters and polarity thresholding method for recombination, the SNR of defects with sizes as small as 2% cross-sectional area (CSA) could be improved significantly.…”

Section: Introductionmentioning

confidence: 99%

Defect Detection using Power Spectrum of Torsional Waves in Guided-Wave Inspection of Pipelines

2019

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Ultrasonic Guided-wave (UGW) testing of pipelines allows long-range assessment of pipe integrity from a single point of inspection. This technology uses a number of arrays of transducers separated by a distance from each other to generate a single axisymmetric (torsional) wave mode. The location of anomalies in the pipe is determined by inspectors using the received signal. Guided-waves are multimodal and dispersive. In practical tests, nonaxisymmetric waves are also received due to the nonideal testing conditions, such as presence of variable transfer function of transducers. These waves are considered as the main source of noise in the guided-wave inspection of pipelines. In this paper, we propose a method to exploit the differences in the power spectrum of the torsional wave and flexural waves, in order to detect the torsional wave, leading to the defect location. The method is based on a sliding moving window, where in each iteration the signals are normalised and their power spectra are calculated. Each power spectrum is compared with the previously known spectrum of excitation sequence. Five binary conditions are defined; all of these need to be met in order for a window to be marked as defect signal. This method is validated using a synthesised test case generated by a Finite Element Model (FEM) as well as real test data gathered from laboratory trials. In laboratory trials, three different pipes with defects sizes of 4%, 3% and 2% cross-sectional area (CSA) material loss were evaluated. In order to find the optimum frequency, the varying excitation frequency of 30 to 50 kHz (in steps of 2 kHz) were used. The results demonstrate the capability of this algorithm in detecting torsional waves with low signal-to-noise ratio (SNR) without requiring any change in the excitation sequence. This can help inspectors by validating the frequency response of the received sequence and give more confidence in the detection of defects in guided-wave testing of pipelines.

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Split-Spectrum Signal Processing for Reduction of the Effect of Dispersive Wave Modes in Long-range Ultrasonic Testing

Cited by 10 publications

References 9 publications

Detection of Defects Using Spatial Variances of Guided-Wave Modes in Testing of Pipes

Detection of Defects Using Spatial Variances of Guided-Wave Modes in Testing of Pipes

Progresses and Challenges of Ultrasonic Testing for Stress in Remanufacturing Laser Cladding Coating

Defect Detection using Power Spectrum of Torsional Waves in Guided-Wave Inspection of Pipelines

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