Laser Ultrasound Inspection Based on Wavelet Transform and Data Clustering for Defect Estimation in Metallic Samples

Laser-generated ultrasound is a modern non-destructive testing technique. It has been investigated over recent years as an alternative to classical ultrasonic methods, mainly in industrial maintenance and quality control procedures. In this study, the detection and reconstruction of internal defects in a metallic sample is performed by means of a time-frequency analysis of ultrasonic waves generated by a laser-induced thermal mechanism. In the proposed methodology, we used wavelet transform due to its multi-resolution time frequency characteristics. In order to isolate and estimate the corresponding time of flight of eventual ultrasonic echoes related to internal defects, a density-based spatial clustering was applied to the resulting time frequency maps. Using the laser scan beam’s position, the ultrasonic transducer’s location and the echoes’ arrival times were determined, the estimation of the defect’s position was carried out afterwards. Finally, clustering algorithms were applied to the resulting geometric solutions from the set of the laser scan points which was proposed to obtain a two-dimensional projection of the defect outline over the scan plane. The study demonstrates that the proposed method of wavelet transform ultrasonic imaging can be effectively applied to detect and size internal defects without any reference information, which represents a valuable outcome for various applications in the industry.

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Improvement of Accuracy in Damage Localization Using Frequency Slice Wavelet Transform

Shock and Vibration ◽

10.1155/2012/174563 ◽

2012 ◽

Vol 19 (4) ◽

pp. 585-596 ◽

Cited By ~ 9

Author(s):

Xinglong Liu ◽

Zhongwei Jiang ◽

Zhonghong Yan

Keyword(s):

Wavelet Transform ◽

Damage Identification ◽

Lamb Waves ◽

Group Velocity Dispersion ◽

Propagation Distance ◽

Primary Objective ◽

Frequency Resolution ◽

Damage Localization ◽

Arrival Times ◽

Time Frequency

Damage localization is a primary objective of damage identification. This paper presents damage localization in beam structure using impact-induced Lamb wave and Frequency Slice Wavelet Transform (FSWT). FSWT is a new time-frequency analysis method and has the adaptive resolution feature. The time-frequency resolution is a vital factor affecting the accuracy of damage localization. In FSWT there is a unique parameter controlling the time-frequency resolution. To improve the accuracy of damage localization, a generalized criterion is proposed to determine the parameter value for achieving a suitable time-frequency resolution. For damage localization, the group velocity dispersion curve (GVDC) of A0Lamb waves in beam is first accurately estimated using FSWT, and then the arrival times of reflection wave from the crack for some individual frequency components are determined. An average operation on the calculated propagation distance is then performed to further improve the accuracy of damage localization.

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Time Frequency Analysis of Dispersive Waves by Means of Wavelet Transform

Journal of Applied Mechanics ◽

10.1115/1.2896009 ◽

1995 ◽

Vol 62 (4) ◽

pp. 841-846 ◽

Cited By ~ 126

Author(s):

Kikuo Kishimoto ◽

Hirotsugu Inoue ◽

Makoto Hamada ◽

Toshikazu Shibuya

Keyword(s):

Wavelet Transform ◽

Frequency Analysis ◽

Gabor Wavelet ◽

Flexural Wave ◽

Lateral Impact ◽

Dispersive Waves ◽

Time Frequency Analysis ◽

Arrival Times ◽

Time Frequency ◽

Wide Range

A new approach is presented for investigating the dispersive character of structural waves. The wavelet transform is applied to the time-frequency analysis of dispersive waves. The flexural wave induced in a beam by lateral impact is considered. It is shown that the wavelet transform using the Gabor wavelet effectively decomposes the strain response into its time-frequency components. In addition, the peaks of the time-frequency distribution indicate the arrival times of waves. By utilizing this fact, the dispersion relation of the group velocity can be accurately identified for a wide range of frequencies.

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Application of Combined Intelligent Algorithm in Load Forecasting

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.945-949.2895 ◽

2014 ◽

Vol 945-949 ◽

pp. 2895-2899

Author(s):

Shi Fang Wang ◽

Hui Cheng Yang

Keyword(s):

Wavelet Transform ◽

Clustering Algorithms ◽

Load Forecasting ◽

Discrete Wavelet ◽

Elman Neural Network ◽

Load Forecast ◽

Time Frequency ◽

Processing Signal ◽

Neural Network Algorithm ◽

Grid Construction

Load forecasting is the foundation of power system planning, accurate load forecasting results can ensure the quality of power supply requirements under the premise of maximum avoid the waste of power grid construction fund, realize the maximization of the social benefits of limited investment. This paper in smart grid environment to load forecast of load signal at the same time, increasing the reliability of the forecast results. The discrete wavelet transform smooth wavelet transform, stationary wavelet transform the redundancy and panning invariability of the time frequency transform, in the process,to avoid the sampling processing signal distortion. In the load forecast this step,use wavelet clustering of data load classification,then use Elman neural network algorithm forecast. The main method is to use wavelet clustering algorithms for load classification. It will greatly enhance the load forecasting results accuracy and dependability.

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A time-frequency analysis algorithm for ultrasonic waves generating from a debonding defect by using empirical wavelet transform

Applied Acoustics ◽

10.1016/j.apacoust.2017.10.002 ◽

2018 ◽

Vol 131 ◽

pp. 16-27 ◽

Cited By ~ 17

Author(s):

Tao Liu ◽

Jian Li ◽

Xiaofeng Cai ◽

Shaoze Yan

Keyword(s):

Wavelet Transform ◽

Frequency Analysis ◽

Ultrasonic Waves ◽

Time Frequency Analysis ◽

Analysis Algorithm ◽

Time Frequency ◽

Empirical Wavelet Transform

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Ultrasonic Methods

10.1007/978-3-030-72192-3_5 ◽

2021 ◽

pp. 87-131

Author(s):

Vykintas Samaitis ◽

Elena Jasiūnienė ◽

Pawel Packo ◽

Damira Smagulova

Keyword(s):

Long Range ◽

Guided Waves ◽

Structural Integrity ◽

Ultrasonic Inspection ◽

Guided Wave ◽

Ultrasonic Waves ◽

Bulk Wave ◽

Destructive Testing ◽

Fibre Breakage ◽

Ultrasonic Methods

AbstractUltrasonic inspection is a well recognized technique for non-destructive testing of aircraft components. It provides both local highly sensitive inspection in the vicinity of the sensor and long-range structural assessment by means of guided waves. In general, the properties of ultrasonic waves like velocity, attenuation and propagation characteristics such as reflection, transmission and scattering depend on composition and structural integrity of the material. Hence, ultrasonic inspection is commonly used as a primary tool for active inspection of aircraft components such as engine covers, wing skins and fuselages with the aim to detect, localise and describe delaminations, voids, fibre breakage and ply waviness. This chapter mainly focuses on long range guided wave structural health monitoring, as aircraft components require rapid evaluation of large components preferably in real time without the necessity for grouding of an aircraft. In few upcoming chapters advantages and shortcommings of bulk wave and guided wave ultrasonic inspection is presented, fundamentals of guided wave propagation and damage detection are reviewed, the reliability of guided wave SHM is discussed and some recent examples of guided wave applications to SHM of aerospace components are given.

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A Study on Characteristics of Leak Signals of Pipeline Using Acoustic Emission Technique

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.110.79 ◽

2006 ◽

Vol 110 ◽

pp. 79-88 ◽

Cited By ~ 4

Author(s):

Min Rae Lee ◽

Joon Hyun Lee

Keyword(s):

Acoustic Emission ◽

Wavelet Transform ◽

Circular Hole ◽

Frequency Component ◽

Acoustic Emission Technique ◽

Acoustic Parameters ◽

Arrival Times ◽

Time Frequency ◽

Aerodynamic Model ◽

Simulation Results

This study presents an approach to leak detection of pipeline review in terms of theoretical analysis such as acoustics and hydromechanics that should be accompanied by explanation of leakage. The acoustic emission signals during leak from circular hole of different geometries were studied both analytically and experimentally. The relationships between acoustic parameters and fluid mechanical parameters also were derived analytically. A quadrupole aerodynamic model was applied for the analysis of leak from the circular hole. Computer simulation results demonstrate the effectiveness of the proposed approach. In addition, it was confirmed that the wavelet transform (WT) was an effective tool to determine source location. That is, arrival times of each frequency component needed in the velocity calculation could be determined from the peak of the magnitude of wavelet transform data on the time-frequency plane.

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Using multi-temporal analysis to classify monthly precipitation based on maximal overlap discrete wavelet transform

Journal of Hydroinformatics ◽

10.2166/hydro.2019.021 ◽

2019 ◽

Vol 21 (4) ◽

pp. 541-557 ◽

Cited By ~ 1

Author(s):

Kiyoumars Roushangar ◽

Farhad Alizadeh

Keyword(s):

Time Series ◽

Wavelet Transform ◽

Discrete Wavelet Transform ◽

Spatial Clustering ◽

Superior Performance ◽

Discrete Wavelet ◽

Monthly Precipitation ◽

Time Frequency ◽

Clustering Model ◽

Multi Temporal

AbstractIn the present study, a hybrid methodology was proposed in which temporal pre-processing and spatial classification approaches were used in a way to take advantage of multiscale properties of precipitation series. Monthly precipitation data (1960–2010) for 31 rain gauges were used in the proposed classification approaches. Maximal overlap discrete wavelet transform (MODWT) was used to capture the time–frequency attributes of the time series and multiscale regionalization was performed by using self-organizing maps (SOM) clustering model. Daubechies 2 function was selected as mother wavelet to decompose the precipitation time series. Also, proper boundary extensions and decomposition level were applied. Different combinations of the wavelet (W) and scaling (V) coefficients were used to determine the input dataset as a basis of spatial clustering. Four input combinations were determined as single-cycle and the remaining four combinations were determined with multi-temporal dataset. These combinations were determined in a way to cover all possible scales captured from MODWT. The proposed model's efficiency in spatial clustering stage was verified using Silhouette Coefficient index. Results demonstrated superior performance of MODWT-SOM in comparison to historical-based SOM approach. It was observed that the clusters captured by MODWT-SOM approach determined homogenous precipitation areas very well (based on physical analysis).

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A fractional Fourier transform analysis of the scattering of ultrasonic waves

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2014.0958 ◽

2015 ◽

Vol 471 (2175) ◽

pp. 20140958 ◽

Cited By ~ 6

Author(s):

Katherine M.M. Tant ◽

Anthony J. Mulholland ◽

Matthias Langer ◽

Anthony Gachagan

Keyword(s):

Fourier Transform ◽

Frequency Domain ◽

Fractional Fourier Transform ◽

Signal To Noise Ratio ◽

Homogeneous Solution ◽

Ultrasonic Waves ◽

Destructive Testing ◽

Time Frequency ◽

Forcing Function ◽

Linear Chirp

Many safety critical structures, such as those found in nuclear plants, oil pipelines and in the aerospace industry, rely on key components that are constructed from heterogeneous materials. Ultrasonic non-destructive testing (NDT) uses high-frequency mechanical waves to inspect these parts, ensuring they operate reliably without compromising their integrity. It is possible to employ mathematical models to develop a deeper understanding of the acquired ultrasonic data and enhance defect imaging algorithms. In this paper, a model for the scattering of ultrasonic waves by a crack is derived in the time–frequency domain. The fractional Fourier transform (FrFT) is applied to an inhomogeneous wave equation where the forcing function is prescribed as a linear chirp, modulated by a Gaussian envelope. The homogeneous solution is found via the Born approximation which encapsulates information regarding the flaw geometry. The inhomogeneous solution is obtained via the inverse Fourier transform of a Gaussian-windowed linear chirp excitation. It is observed that, although the scattering profile of the flaw does not change, it is amplified. Thus, the theory demonstrates the enhanced signal-to-noise ratio permitted by the use of coded excitation, as well as establishing a time–frequency domain framework to assist in flaw identification and classification.

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Health Monitoring of Laminate Plates with AE Signals and Wave Propagation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.47-50.306 ◽

2008 ◽

Vol 47-50 ◽

pp. 306-309 ◽

Cited By ~ 1

Author(s):

Chao Du ◽

Toshiaki Natsuki ◽

Qing Qing Ni

Keyword(s):

Wave Propagation ◽

Wavelet Transform ◽

Health Monitoring ◽

Plate Theory ◽

Plate Thickness ◽

Laminate Plate ◽

Arrival Times ◽

Time Frequency ◽

Ae Signal ◽

Plate Waves

Based on Laminate plate theory, a formulation, including the effects of shear deformation and rotary inertia on the characterization of plate wave propagation, was derived. The characteristics of plate waves propagating were investigated and the influences of frequency, plate thickness and propagating direction were clearly known. A health monitoring system was built and the plate waves generated by lead break source were received by acoustic emission (AE) sensors. By the wavelet transform [1], the time-frequency domain of AE signal was derived. For a certain frequency, the first peak of the magnitude of wavelet transform indicates the arrival times of plate waves. The locations of lead break source and the delaminations of plate were compared with the predictions of theory.

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