A frequency-wavenumber domain analysis for Lamb wave crack detection

2015 ◽  
pp. 121-126
Keyword(s):  
Lamb Wave ◽  
Crack Detection ◽  
Domain Analysis ◽  
Wavenumber Domain

Asymmetric propagation of the first order antisymmetric lamb wave in a tapered plate based on time domain analysis

2017 ◽  
Vol 63 (4) ◽  
pp. 393-401 ◽  
Author(s):  
Shao-Yong Huo ◽  
Jiu-Jiu Chen ◽  
Guang-Huang Song ◽  
Xu Han
Keyword(s):  
Time Domain ◽  
Lamb Wave ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
First Order

scholarly journals Lamb Wave Local Wavenumber Approach for Characterizing Flat Bottom Defects in an Isotropic Thin Plate

2018 ◽  
Vol 8 (9) ◽  
pp. 1600 ◽  
Author(s):  
Guopeng Fan ◽  
Haiyan Zhang ◽  
Hui Zhang ◽  
Wenfa Zhu ◽  
Xiaodong Chai
Keyword(s):  
Thin Plate ◽  
Lamb Wave ◽  
Spatial Information ◽  
Laser Doppler Vibrometer ◽  
Target Area ◽  
Flat Bottom ◽  
Wavenumber Domain ◽  
Time Space ◽  
Local Wavenumber ◽  
Rectangular Groove

This paper aims to use the Lamb wave local wavenumber approach to characterize flat bottom defects (including circular flat bottom holes and a rectangular groove) in an isotropic thin plate. An air-coupled transducer (ACT) with a special incidence angle is used to actuate the fundamental anti-symmetric mode (A0). A laser Doppler vibrometer (LDV) is employed to measure the out-of-plane velocity over a target area. These signals are processed by the wavenumber domain filtering technique in order to remove any modes other than the A0 mode. The filtered signals are transformed back into the time-space domain. The space-frequency-wavenumber spectrum is then obtained by using three-dimensional fast Fourier transform (3D FFT) and a short space transform, which can retain the spatial information and reduce the magnitude of side lobes in the wavenumber domain. The average wavenumber is calculated, as a real signal usually contains a certain bandwidth instead of the singular frequency component. Both simulation results and experimental results demonstrate that the average wavenumber can be used not only to identify shape, location, and size of the damage, but also quantify the depth of the damage. In addition, the direction of an inclined rectangular groove is obtained by calculating the image moments under grayscale. This hybrid and non-contact system based on the local wavenumber approach can be provided with a high resolution.

Numerical Investigation of Nonlinear Lamb Wave Time Reversing for Fatigue Crack Detection

2019 ◽  
Author(s):  
Junzhen Wang ◽  
Yanfeng Shen
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Time Reversal ◽  
Lamb Wave ◽  
Crack Detection ◽  
Guided Waves ◽  
Fatigue Cracks ◽  
Contact Dynamics ◽  
Virtual Time ◽  
Fatigue Crack Detection

Abstract This paper presents a numerical study on nonlinear Lamb wave time reversing for fatigue crack detection. An analytical framework is initially presented, modeling Lamb wave generation, propagation, wave crack linear and nonlinear interaction, and reception. Subsequently, a 3D transient dynamic coupled-field finite element model is constructed to simulate the pitch-catch procedure in an aluminum plate using the commercial finite element software (ANSYS). The excitation frequency is carefully selected, where only single Lamb wave mode will be generated by the Piezoelectric Wafer Active Sensor (PWAS). The fatigue cracks are modelled nucleating from both sides of a rivet hole. In addition, contact dynamics are considered to capture the nonlinear interactions between guided waves and the fatigue cracks, which would induce Contact Acoustic Nonlinearity (CAN) into the guided waves. Then the conventional and virtual time reversal methods are realized by finite element simulation. Advanced signal processing techniques are used to extract the distinctive nonlinear features. Via the Fast Fourier Transform (FFT) and time-frequency spectral analysis, nonlinear superharmonic components are observed. The reconstructed signals attained from the conventional and virtual time reversal methods are compared and analyzed. Finally, various Damage Indices (DIs), based on the difference between the reconstructed signal and the excitation waveform as well as the amplitude ratio between the superharmonic and the fundamental frequency components are adopted to evaluate the fatigue crack severity. The DIs could provide quantitative diagnostic information for fatigue crack detection. This paper finishes with summary, concluding remarks, and suggestions for future work.

Lamb Wave Propagation Study Using Frequency-Wavenumber Analysis

2012 ◽  
Author(s):  
Zhenhua Tian ◽  
Lingyu Yu
Keyword(s):  
Wave Propagation ◽  
Lamb Wave ◽  
Experimental Testing ◽  
Wave Spectrum ◽  
Laser Doppler Vibrometer ◽  
Wave Mode ◽  
Wavenumber Domain ◽  
Time Space ◽  
Lamb Wave Propagation ◽  
Wave Modes

Lamb waves are dispersive and multi-modal. Various wave modes make the interpretation of Lamb wave signal very difficult. It is desired that different modes can be separated for individual analysis. In the this paper, we present our studies on the multimodal Lamb wave propagation and wave mode extraction using frequency-wavenumber analysis. Wave spectrum in the frequency-wavenumber domain shows clear distinction among Lamb wave modes being present. This allows separating them or extracting a desired Lamb wave mode through a novel filtering strategy. Thus a single mode Lamb can be identified and extracted for certain types of damage detection in structural health monitoring (SHM). These concepts are illustrated through experimental testing. A scanning laser Doppler vibrometer is used to acquiring the time-space wavefield regarding the multimodal Lamb wave propagation. Then the recorded wavefield was analyzed in frequency-wavenumber domain and decomposed into different wave modes.

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