scholarly journals Nonpenetrating Damage Identification Using Hybrid Lamb Wave Modes from Hilbert-Huang Spectrum in Thin-Walled Structures

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Zijian Wang ◽  
Pizhong Qiao ◽  
Binkai Shi
Keyword(s):  
Lamb Wave ◽  
Damage Identification ◽  
Lamb Waves ◽  
Wave Mode ◽  
Thin Walled Structures ◽  
Damage Indices ◽  
Thin Walled ◽  
Experimental Validations ◽  
The One ◽  
Wave Modes

Lamb waves have shown promising advantages for damage identification in thin-walled structures. Multiple modes of Lamb wave provide diverse sensitivities to different types of damage. To sufficiently utilize damage-related wave features, damage indices were developed by using hybrid Lamb wave modes from Hilbert-Huang spectra. Damage indices were defined as surface integrals of Hilbert-Huang spectra on featured regions determined by time and frequency windowing. The time windowing was performed according to individual propagation velocity of different Lamb wave mode, while the frequency windowing was performed according to the frequency of excitation. By summing damage indices for all transmitter-receiver pairs, pixels were calculated to reconstruct a damage map to characterize the degree of damage at each location on structure. Both numerical and experimental validations were conducted to identify a nonpenetrating damage. The results demonstrated that the proposed damage indices using hybrid Lamb wave modes are more sensitive and robust than the one using single Lamb wave mode.

Damage Detection Using Lamb Waves (Review)

2014 ◽  
Vol 1028 ◽  
pp. 161-166 ◽  
Author(s):  
Zai Lin Yang ◽  
Hamada M. Elgamal ◽  
Yao Wang
Keyword(s):  
Damage Detection ◽  
Health Monitoring ◽  
Guided Waves ◽  
Damage Identification ◽  
Lamb Waves ◽  
Long Distance ◽  
The Past ◽  
Thin Walled Structures ◽  
Thin Walled ◽  
Analytical Complexity

Several techniques have been researched for detecting damage in plates. Each of these techniques offers their own unique advantages in detecting certain types of damage with various levels of analytical complexity. Lamb waves are guided waves that exist in thin walled structures. Because this type of wave can travel long distance with little attenuation, they have been studied intensively for structural health monitoring, especially in the past few decades. This paper presents an overview of using the Lamb waves in damage detection including the theory of lamb waves and the lamb-wave-based damage identification.

scholarly journals Lamb Wave Scattering Analysis for Interface Damage Detection between a Surface-Mounted Block and Elastic Plate

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 860
Author(s):  
Mikhail V. Golub ◽  
Alisa N. Shpak ◽  
Inka Mueller ◽  
Sergey I. Fomenko ◽  
Claus-Peter Fritzen
Keyword(s):  
Damage Detection ◽  
Elastic Plate ◽  
Lamb Wave ◽  
Wave Scattering ◽  
Hybrid Approach ◽  
Guided Wave ◽  
Open Crack ◽  
Damage Indices ◽  
Impulse Function ◽  
Thin Walled

Since stringers are often applied in engineering constructions to improve thin-walled structures’ strength, methods for damage detection at the joints between the stringer and the thin-walled structure are necessary. A 2D mathematical model was employed to simulate Lamb wave excitation and sensing via rectangular piezoelectric-wafer active transducers mounted on the surface of an elastic plate with rectangular surface-bonded obstacles (stiffeners) with interface defects. The results of a 2D simulation using the finite element method and the semi-analytical hybrid approach were validated experimentally using laser Doppler vibrometry for fully bonded and semi-debonded rectangular obstacles. A numerical analysis of fundamental Lamb wave scattering via rectangular stiffeners in different bonding states is presented. Two kinds of interfacial defects between the stiffener and the plate are considered: the partial degradation of the adhesive at the interface and an open crack. Damage indices calculated using the data obtained from a sensor are analyzed numerically. The choice of an input impulse function applied at the piezoelectric actuator is discussed from the perspective of the development of guided-wave-based structural health monitoring techniques for damage detection.

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

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2745 ◽  
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.

scholarly journals Leaky Lamb Wave Radiation from a Waveguide Plate with Finite Width

2020 ◽  
Vol 10 (22) ◽  
pp. 8104
Author(s):  
Sang-Jin Park ◽  
Hoe-Woong Kim ◽  
Young-Sang Joo
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Wave Radiation ◽  
Finite Width ◽  
Propagation Characteristics ◽  
Radiation Characteristics ◽  
Radiation Beam ◽  
Leaky Lamb Wave ◽  
Waveguide Sensor

In this paper, leaky Lamb wave radiation from a waveguide plate with finite width is investigated to gain a basic understanding of the radiation characteristics of the plate-type waveguide sensor. Although the leaky Lamb wave behavior has already been theoretically revealed, most studies have only dealt with two dimensional radiations of a single leaky Lamb wave mode in an infinitely wide plate, and the effect of the width modes (that are additionally formed by the lateral sides of the plate) on leaky Lamb wave radiation has not been fully addressed. This work aimed to explain the propagation behavior and characteristics of the Lamb waves induced by the existence of the width modes and to reveal their effects on leaky Lamb wave radiation for the performance improvement of the waveguide sensor. To investigate the effect of the width modes in a waveguide plate with finite width, propagation characteristics of the Lamb waves were analyzed by the semi-analytical finite element (SAFE) method. Then, the Lamb wave radiation was computationally modeled on the basis of the analyzed propagation characteristics and was also experimentally measured for comparison. From the modeled and measured results of the leaky radiation beam, it was found that the width modes could affect leaky Lamb wave radiation with the mode superposition and radiation characteristics were significantly changed depending on the wave phase of the superposed modes on the radiation surface.

scholarly journals The Rapid Detection Technology of Lamb Wave for Microcracks in Thin-Walled Tubes

2019 ◽  
Vol 9 (17) ◽  
pp. 3576 ◽  
Author(s):  
Yang ◽  
Wang ◽  
Yang
Keyword(s):  
Lamb Wave ◽  
Rapid Detection ◽  
Detection Method ◽  
Lamb Waves ◽  
Thin Plates ◽  
Depth Information ◽  
Amplitude Curve ◽  
Dispersion Characteristics ◽  
Detection Technology ◽  
Thin Walled

Thin-walled tubes are a kind of pressure vessel formed by a stamping and drawing process, which must withstand a great deal of sudden pressure during use. When microcrack defects of a certain depth are present on its inner and outer surfaces, severe safety accidents may occur, such as cracking and crushing. Therefore, it is necessary to carry out nondestructive testing of thin-walled tubes in the production process to eliminate the potential safety hazards. To realize the rapid detection of microcracks in thin-walled tubes, this study could be summarized as follows: (i) Because the diameters of the thin-walled tubes were much larger than their thicknesses, Lamb wave characteristics of plates with equal thicknesses were used to approximate the dispersion characteristics of thin-walled tubes. (ii) To study the dispersion characteristics of Lamb waves in thin plates, the detection method of the mode was determined using the particle displacement–amplitude curve. (iii) Using a multi-channel parallel detection method, rapid detection equipment for Lamb wave microcracks in thin-walled tubes was developed. (iv) The filtering peak values for defect signal detection with different depths showed that the defect detection peak values could reflect the defect depth information. (v) According to the minimum defect standard of a 0.045-mm depth, 100,000 thin-walled tubes were tested. The results showed that the missed detection rate was 0%, the reject rate was 0.3%, and the detection speed was 5.8 s/piece, which fully meets the actual detection requirements of production lines. Therefore, this study not only solved the practical issues for the rapid detection of microcracks in thin-walled tubes but also provided a reference for the application of ultrasonic technology for the detection of other components.

Suppressing Technique of the Antisymmetric Mode by the Superposition of Lamb Waves Generated by Two Laser Beams in a Thin Plate

2006 ◽  
Vol 321-323 ◽  
pp. 103-107
Author(s):  
Seung Seok Lee ◽  
Sang Whoe Dho
Keyword(s):  
Thin Plate ◽  
Opposite Direction ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Laser Beams ◽  
Symmetric Mode ◽  
Antisymmetric Mode

We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.

Structural Health Monitoring of Thin Aluminum Plate Using Acoustic Sensors

2012 ◽  
Vol 622-623 ◽  
pp. 1389-1395
Author(s):  
R. Nishanth ◽  
K. Lingadurai ◽  
V. Malolan ◽  
Gowrishankar Wuriti ◽  
M.R.M. Babu
Keyword(s):  
Lamb Wave ◽  
Damage Identification ◽  
Lamb Waves ◽  
Time Domain Analysis ◽  
Ultrasonic Waves ◽  
Aluminum Plate ◽  
Identification System ◽  
Time Frequency ◽  
Thin Aluminum ◽  
Aluminum Plates

SHM is defined as “an emerging technology that can be defined as continuous, autonomous, real time, in-service monitoring of the physical condition of a structure by means of embedded or attached sensors with minimum manual intervention” .SHM provides the ability of a system to detect adverse changes within a system’s structure to enhance reliability and reduce maintenance costs. There are different Non-Destructive techniques like acoustic emission, ultrasonic, acousto-ultrasonic, guided ultrasonic waves or Lamb waves which are nowadays investigated for the development of an efficient and user-friendly damage identification system. This paper deals with the latter which is based on Lamb wave propagation. It has been developed especially for distinguishing different kinds of damages. The Lamb wave-based active SHM method uses piezoelectric (PZT) sensors to transmit and receive Lamb waves in a thin Aluminum plate. The Lamb wave modes (AO &SO) travel into the structure and are reflected by the structural boundaries, discontinuities, and damage. By studying their propagation and reflection, the presence of defect in the structure is determined. Laboratory level experiments have been carried out on thin Aluminum plates with angular, horizontal and vertical defect. The obtained waveform is filtered to avoid unwanted noise & disturbances using Savitzky-Golay filtering. The filtered waveforms are compared to differentiate the defects. Short Time Fourier Transform has been carried out on the acquired waveform. This study provides significant insight into the problem of identifying localized damages in the structure using PZT and dispersion of signal after they interact with different types of damage. Those small defects like the horizontal one that may be nearly missed in time domain analysis can also be clearly identified in the STFT analysis. Moreover the occurrence of So mode is also clearly seen. Thus, Lamb waves generated by PZT sensors and time-frequency analysis techniques could be used effectively for damage detection in aluminum plate. This study has given a complete idea of the working and the basic requirements of SHM system.

FEA-based Guided Wave Mode Optimization for Damage Detection on Thin-walled Structures

2018 ◽  
Vol 38 (5) ◽  
pp. 299-307
Author(s):  
Seongin Moon ◽  
To Kang ◽  
Soonwoo Han ◽  
Jun-Young Jeon ◽  
Gyuhae Park
Keyword(s):  
Damage Detection ◽  
Wave Mode ◽  
Guided Wave ◽  
Thin Walled Structures ◽  
Thin Walled

Dispersion curve analysis method for Lamb wave mode separation

2019 ◽  
Vol 19 (5) ◽  
pp. 1590-1601
Author(s):  
Yue Hu ◽  
Yanping Zhu ◽  
Xiaotong Tu ◽  
Jing Lu ◽  
Fucai Li
Keyword(s):  
Dispersion Curve ◽  
Lamb Wave ◽  
Hessian Matrix ◽  
Wave Mode ◽  
Curve Analysis ◽  
Energy Concentration ◽  
Time Frequency ◽  
Mode Separation ◽  
Multimodal Features ◽  
Wave Modes

The Lamb wave inspection has emerged as a promising method for structural health monitoring and nondestructive testing. However, because of the highly dispersive and multimodal features, the Lamb wave mode separation has become a challenging problem. Based on the dispersion curve analysis, a new signal processing method is proposed in this study to solve this problem. First, a novel function based on the Hessian matrix is constructed to enhance the energy concentration of the dispersion curve in the time–frequency representation to reduce the dispersion effect. Subsequently, the constrained penalty function algorithm is developed for detecting dispersion curves. Finally, a mode reconstruction algorithm is developed to recover Lamb wave modes. The proposed method can separate overlapping wave modes and detect the crack fault by enhancing the time–frequency feature of the Lamb wave signal. Two experiments are carried out to verify the effectiveness of the proposed method for Lamb wave mode separation.

Static strain-based identification of extensive damages in thin-walled structures

2021 ◽  
pp. 147592172110506
Author(s):  
Nicholas E. Silionis ◽  
Konstantinos N. Anyfantis
Keyword(s):  
Damage Identification ◽  
Identification Problem ◽  
Static Strain ◽  
Guiding Principle ◽  
Thin Walled Structures ◽  
Statistical Pattern ◽  
Bending Stresses ◽  
Thin Walled ◽  
Numerical Finite Element ◽  
Identification Strategy

Interest has been expressed during the past few years toward incorporating structural health monitoring (SHM) systems in ship hull structures for detecting damages that cause significant load-carrying reductions and subsequent load redistributions. The guiding principle of the damage identification strategy considered in this work is based upon measuring, through a limited number of sensors, the static strain redistributions caused by an extensive damage. The problem is tackled as a statistical pattern recognition one, and therefore, methods sourcing from machine learning (ML) are applied. The SHM strategy is both virtually and experimentally applied to a thin-walled prismatic geometry that represents an idealized hull form solely subjected to principal bending stresses (sagging/hogging). Damage modes causing extensive stress redistribution, are abstractly represented by a circular discontinuity. The damage identification problem is treated in a hierarchical order, initialized by damage detection and moving to an increasingly more localized prediction of the damage location. Training datasets for the ML tools are generated from numerical finite element simulations. Measurement uncertainty is propagated in the theoretical strains by information inferred from experimental data. Two different sensor architectures were assessed. An experimental programme is performed for testing the accuracy of the proposed damage identification strategy, yielding promising results and providing valuable insights.

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