Damage imaging of composite structures using multipath scattering Lamb waves

Guided waves (GW) based methods are a promising tool for structural health monitoring (SHM) of plate-like metallic and composite structures in which high safety standards are required. In this paper we present research with the aim to design and manufacture a prototype of Lamb waves (LW) SHM system. Two approaches can be applied for SHM of plate-like structures. One of them can be based on a sparse array and damage imaging involving incoherent summation of signals envelope. The second approach involves phased arrays with transducers spaced at a distance lower than half wavelength of the excited Lamb-mode. The influence of an arrays parameters on beamforming of Lamb waves is discussed in the case of linear array. It appears that an unequivocal localization of damage on a plate requires a 2D arrays topology; therefore a star-shaped active array was designed and manufactured for the developed SHM system. Two signal processing approaches were applied for that array, the standard one, based on the delay and sum (DAS) synthetic aperture focusing scheme, and the second one, using a self-focusing technique to obtain the separate images for each scatterer existing in the plate.

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Identification of damage in composite structures using Gaussian mixture model-processed Lamb waves

Smart Materials and Structures ◽

10.1088/1361-665x/aaaf96 ◽

2018 ◽

Vol 27 (4) ◽

pp. 045007 ◽

Cited By ~ 6

Author(s):

Qiang Wang ◽

Shuxian Ma ◽

Dong Yue

Keyword(s):

Gaussian Mixture Model ◽

Mixture Model ◽

Composite Structures ◽

Lamb Waves ◽

Gaussian Mixture

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Damage Identification of Large Generator Stator Insulation Based on PZT Sensor Systems and Hybrid Features of Lamb Waves

Sensors ◽

10.3390/s18092745 ◽

2018 ◽

Vol 18 (9) ◽

pp. 2745 ◽

Cited By ~ 6

Author(s):

Ruihua Li ◽

Hao Li ◽

Bo Hu

Keyword(s):

Power Systems ◽

Lamb Wave ◽

Damage Identification ◽

Lamb Waves ◽

Fem Simulation ◽

Correlation Coefficients ◽

Hybrid Features ◽

Material Inhomogeneity ◽

Time Frequency ◽

Damage Imaging

Large generators are the principal pieces of equipment in power systems, and their operation reliability critically depends on the stator insulation. Damages in stator insulation will gradually lead to the failure and breakdown of generator. Due to the advantages of Lamb waves in Structural health monitoring (SHM), in this study, a distributed piezoelectric (PZT) sensor system and hybrid features of the Lamb waves are introduced to identify stator insulation damage of large generator. A hierarchical probability damage-imaging (PDI) algorithm is proposed to tackle the material inhomogeneity and anisotropy of the stator insulation. The proposed method includes three steps: global detection using correlation coefficients, local detection using Time of flight (ToF) along with the amplitude of damage-scattered Lamb wave, and final images fusion. Wavelet Transform was used to extract the ToF of Lamb wave in terms of the time-frequency domain. Finite Element Modeling (FEM) simulation and experimental work were carried out to identify four typical stator insulation damages for validation, including inner void, inner delamination, puncture, and crack. Results show that the proposed method can precisely identify the location of stator insulation damage, and the reconstruction image can be used to identify the size of stator insulation damage.

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A Method of Dispersion Compensation Based on Warped Frequency Transform

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.718-720.2062 ◽

2013 ◽

Vol 718-720 ◽

pp. 2062-2067 ◽

Cited By ~ 2

Author(s):

Shang Chen Fu ◽

Zhen Jian Lv ◽

Ding Ma ◽

Li Hua Shi

Keyword(s):

High Resolution ◽

Velocity Dispersion ◽

Lamb Waves ◽

Group Velocity Dispersion ◽

Dispersion Compensation ◽

Imaging Method ◽

Finite Element Software ◽

Damage Imaging ◽

Resolution Imaging ◽

Multi Mode

The use of Lamb waves for structural health monitoring (SHM) has complicated by its multi-mode character and dispersion effect, which impacts the damage positioning and high-resolution imaging. The group velocity dispersion curves of Lamb waves can be employed to warp the frequency axis, and then to establish warped frequency transform (WFT) to process Lamb waves. In this paper, received signals are directly compensated with warped frequency transform to suppress dispersion, and a new imaging method is proposed based on warped frequency transform. The propagation of Lamb waves in damaged aluminum plate is simulated by finite element software ABAQUS, results show that warped frequency transform can effectively compensate dispersive wave-packets, and high-resolution damage imaging can be obtained by the proposed method.

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Modeling of Lamb Waves in Composite Structures

Encyclopedia of Structural Health Monitoring ◽

10.1002/9780470061626.shm071 ◽

2008 ◽

Author(s):

Abir Chakraborty

Keyword(s):

Composite Structures ◽

Lamb Waves

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The Effect of Ply Orientation and Damage Detection in Composite Stiffened Panel Using Lamb Waves

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.298.161 ◽

2019 ◽

Vol 298 ◽

pp. 161-166

Author(s):

Ouadia Mouhat ◽

Abdelmajid Bybi ◽

Ahmed El Bouhmidi ◽

Hasnae Boubel ◽

Omaima Elmrabet ◽

...

Keyword(s):

Acoustic Waves ◽

Composite Structures ◽

Laminate Composite ◽

Lamb Waves ◽

Stiffened Panel ◽

Signal Acquisition ◽

Frequency Increase ◽

Stiffened Panels ◽

Composite Stiffened Panel ◽

Ply Orientation

The present work proposes a vibration study with different surface and layers orientations at 0°, 15°, 30°, 45°, 60°, 75° and 90°using the Abaqus finite element code, the frequencies Stratified laminate composite panels were studied and the comparison between damaged structures and perfect structures we used stiffened panels based on T-shaped reinforced fibers. Lamb waves (LW) were widely proposed for the long-range inspection of Structural Structural Health Monitoring (SHM) oriented composite structures, the obtained results show the angle effects on the natural frequency increase at a peak then decrease in the form of a sinusoidal half-curve and the numerical results found in this work can be compared to those of other authors in the same area of research, A piezoelectric actuator is used to design acoustic waves and a sensor is used for signal acquisition.

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Impact Localisation in Composite Plates of Different Stiffness Impactors under Simulated Environmental and Operational Conditions

Sensors ◽

10.3390/s19173659 ◽

2019 ◽

Vol 19 (17) ◽

pp. 3659 ◽

Cited By ~ 7

Author(s):

Seno ◽

Aliabadi

Keyword(s):

Composite Structures ◽

Lamb Waves ◽

Real Life ◽

Composite Plates ◽

Information Criterion ◽

Reference Database ◽

Time Of Arrival ◽

Operational Conditions ◽

Contact Behaviour ◽

Using Data

A parametric investigation of the effect of impactor stiffness as well as environmental and operational conditions on impact contact behaviour and the subsequently generated lamb waves in composite structures is presented. It is shown that differing impactor stiffness generates the most significant changes in contact area and lamb wave characteristics (waveform, frequency, and amplitude). A novel impact localisation method was developed based on the above observations that allows for variations due to differences in impactor stiffness based on modifications of the reference database method and the Akaike Information Criterion (AIC) time of arrival (ToA) picker. The proposed method was compared against a benchmark method based on artificial neural networks (ANNS) and the normalised smoothed envelope threshold (NSET) ToA extraction method. The results indicate that the proposed method had comparable accuracy to the benchmark method for hard impacts under various environmental and operational conditions when trained only using a single hard impact case. However, when tested with soft impacts, the benchmark method had very low accuracy, whilst the proposed method was able to maintain its accuracy at an acceptable level. Thus, the proposed method is capable of detecting the location of impacts of varying stiffness under various environmental and operational conditions using data from only a single impact case, which brings it closer to the application of data driven impact detection systems in real life structures.

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