Time-frequency representations of Lamb waves

Niethammer, Marc; Jacobs, Laurence J.; Qu, Jianmin; Jarzynski, Jacek

doi:10.1121/1.1357813

Cited by 231 publications

(113 citation statements)

References 14 publications

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“…Our own previous publication describes an explicit method for determining two arrival times from synthetic or experimental data based on the Wigner-Ville distribution [5]. Niethammer et al [6] provides a detailed comparison of the characteristics and relative merits of different time-frequency representations, including the Fourier spectrogram, wavelet scalogram, Wigner-Ville distribution, and Hilbert spectrum. Hurlebaus et al [7] introduced and Benz et al [8] refined an autonomous correlation-based technique for locating a notch based on time-frequency analysis of notch-scattered laser pulse-generated Lamb modes.…”

Section: Introductionmentioning

confidence: 99%

Automatic determination of acoustic plate source-detector separation from one waveform

Holland

Sachse

2006

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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We discuss an automated procedure for determining the separation between a transient acoustic source and a detector on a plate. We use a time-estimation algorithm based on the assumption that the detected signal is represented by a small, finite number of discrete band-limited impulses. This is carried out using the MUSIC (multiple signal classification) algorithm in time-estimation mode to automatically estimate both the first arrival time of the lowest order antisymmetric (A/sub 0/) mode and the arrival time of the Rayleigh wave. Using the material and geometric properties of the plate and these two arrival times, we calculated the distance to the source. This technique allows the automatic determination of source-receiver separation from a single transient waveform. AbstractWe discuss an automated procedure for determining the separation between a transient acoustic source and a detector on a plate. We use a time-estimation algorithm based on the assumption that the detected signal is represented by a small finite number of discrete band-limited impulses. This is carried out using the MUSIC (MUltiple SIgnal Classification) algorithm in time-estimation mode to automatically estimate both the first arrival time of the lowest order antisymmetric (A 0 ) mode and the arrival time of the Rayleigh wave. Using the material and geometric properties of the plate and these two arrival times we calculate the distance to the source. This technique allows the automatic determination of source-receiver separation from a single transient waveform.

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Section: Introductionmentioning

confidence: 99%

Automatic determination of acoustic plate source-detector separation from one waveform

Holland

Sachse

2006

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…[24][25][26] It has been reported that the arrival time for group velocity at specific frequencies can be obtained by determining the magnitude of the coefficients. The theory and physical meaning of STFT derived data are discussed in the literature.…”

Section: B Experiments Data Analysismentioning

confidence: 99%

Higher order acoustoelastic Lamb wave propagation in stressed plates

Pei

Bond

2016

The Journal of the Acoustical Society of America

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Modeling and experiments are used to investigate Lamb wave propagation in the direction perpendicular to an applied stress. Sensitivity, in terms of changes in velocity, for both symmetrical and anti-symmetrical modes was determined. Codes were developed based on analytical expressions for waves in loaded plates and they were used to give wave dispersion curves. The experimental system used a pair of compression wave transducers on variable angle wedges, with set separation, and variable frequency tone burst excitation, on an aluminum plate 0.16 cm thick with uniaxial applied loads. The loads, which were up to 600 με, were measured using strain gages. Model results and experimental data are in good agreement. It was found that the change in Lamb wave velocity, due to the acoustoelastic effect, for the S1 mode exhibits about ten times more sensitive, in terms of velocity change, than the traditional bulk wave measurements, and those performed using the fundamental Lamb modes. The data presented demonstrate the potential for the use of higher order Lamb modes for online industrial stress measurement in plate, and that the higher sensitivity seen offers potential for improved measurement systems.

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“…In fact, the features are inputs for any pattern recognition algorithm [121] While Fourier analysis only reveals the frequency content of the signal, it does not provide any information about when each of the components arrived to the sensor. In the Various techniques [122] have been used to isolate multiple closely space guided wave modes in time and frequency. Recently, wavelet transform has emerged as a very important signal processing technique for feature extraction and the selection of signals [123].…”

Section: Detection Of Structural Defects With Shm Methodsmentioning

confidence: 99%

Development of New Structural Health Monitoring Techniques

Fekrmandi¹

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During the past two decades, many researchers have developed methods for the detection of structural defects at the early stages to operate the aerospace vehicles safely and to reduce the operating costs. The Surface Response to Excitation (SuRE) method is one of these approaches developed at FIU to reduce the cost and size of the equipment.The SuRE method excites the surface at a series of frequencies and monitors the propagation characteristics of the generated waves. The amplitude of the waves reaching to any point on the surface varies with frequency; however, it remains consistent as long as the integrity and strain distribution on the part is consistent. These spectral characteristics change when cracks develop or the strain distribution changes. The SHM methods may be used for many applications, from the detection of loose screws to the monitoring of manufacturing operations.A scanning laser vibrometer was used in this study to investigate the characteristics of the spectral changes at different points on the parts. The study started with detecting a load on a plate and estimating its location. The modifications on the part with manufacturing operations were detected and the Part-Based Manufacturing Process vii Performance Monitoring (PbPPM) method was developed. Hardware was prepared to demonstrate the feasibility of the proposed methods in real time.Using low-cost piezoelectric elements and the non-contact scanning laser vibrometer successfully, the data was collected for the SuRE and PbPPM methods.Locational force, loose bolts and material loss could be easily detected by comparing the spectral characteristics of the arriving waves. On-line methods used fast computational methods for estimating the spectrum and detecting the changing operational conditions from sum of the squares of the variations. Neural networks classified the spectrums when the desktop -DSP combination was used. The results demonstrated the feasibility of the SuRE and PbPPM methods.

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Time-frequency representations of Lamb waves

Cited by 231 publications

References 14 publications

Automatic determination of acoustic plate source-detector separation from one waveform

Automatic determination of acoustic plate source-detector separation from one waveform

Higher order acoustoelastic Lamb wave propagation in stressed plates

Development of New Structural Health Monitoring Techniques

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