Time-frequency spectrum segmentation method for separating multimodal guided waves in long bones

2012 ◽  
Vol 131 (4) ◽  
pp. 3425-3425
Author(s):  
Zhenggang Zhang ◽  
Dean Ta ◽  
Weiqi Wang
Keyword(s):  
Frequency Spectrum ◽  
Guided Waves ◽  
Long Bones ◽  
Segmentation Method ◽  
Time Frequency

scholarly journals Strain Sensitivity Enhancement of Broadband Ultrasonic Signals in Plates Using Spectral Phase Filtering

2021 ◽  
Vol 11 (6) ◽  
pp. 2582
Author(s):  
Lucas M. Martinho ◽  
Alan C. Kubrusly ◽  
Nicolás Pérez ◽  
Jean Pierre von der Weid
Keyword(s):  
Fourier Transform ◽  
Guided Waves ◽  
Strain Level ◽  
Energy Concentration ◽  
Short Time Fourier Transform ◽  
Time Frequency ◽  
Frequency Representation ◽  
The Fourier Transform ◽  
Short Time ◽  
Sensitivity Gain

The focused signal obtained by the time-reversal or the cross-correlation techniques of ultrasonic guided waves in plates changes when the medium is subject to strain, which can be used to monitor the medium strain level. In this paper, the sensitivity to strain of cross-correlated signals is enhanced by a post-processing filtering procedure aiming to preserve only strain-sensitive spectrum components. Two different strategies were adopted, based on the phase of either the Fourier transform or the short-time Fourier transform. Both use prior knowledge of the system impulse response at some strain level. The technique was evaluated in an aluminum plate, effectively providing up to twice higher sensitivity to strain. The sensitivity increase depends on a phase threshold parameter used in the filtering process. Its performance was assessed based on the sensitivity gain, the loss of energy concentration capability, and the value of the foreknown strain. Signals synthesized with the time–frequency representation, through the short-time Fourier transform, provided a better tradeoff between sensitivity gain and loss of energy concentration.

scholarly journals A Signal Decomposition Method for Ultrasonic Guided Wave Generated from Debonding Combining Smoothed Pseudo Wigner-Ville Distribution and Vold–Kalman Filter Order Tracking

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Junhua Wu ◽  
Xinglin Chen ◽  
Zheshu Ma
Keyword(s):  
Kalman Filter ◽  
Guided Waves ◽  
Guided Wave ◽  
Signal Decomposition ◽  
Frequency Resolution ◽  
Time Frequency ◽  
Filter Order ◽  
Order Tracking ◽  
Simulation Signal ◽  
Carbon Fibre Composites

Carbon fibre composites have a promising application future of the vehicle, due to its excellent physical properties. Debonding is a major defect of the material. Analyses of wave packets are critical for identification of the defect on ultrasonic nondestructive evaluation and testing. In order to isolate different components of ultrasonic guided waves (GWs), a signal decomposition algorithm combining Smoothed Pseudo Wigner-Ville distribution and Vold–Kalman filter order tracking is presented. In the algorithm, the time-frequency distribution of GW is first obtained by using Smoothed Pseudo Wigner-Ville distribution. The frequencies of different modes are computed based on summation of the time-frequency coefficients in the frequency direction. On the basis of these frequencies, isolation of different modes is done by Vold–Kalman filter order tracking. The results of the simulation signal and the experimental signal reveal that the presented algorithm succeeds in decomposing the multicomponent signal into monocomponents. Even though components overlap in corresponding Fourier spectrum, they can be isolated by using the presented algorithm. So the frequency resolution of the presented method is promising. Based on this, we can do research about defect identification, calculation of the defect size, and locating the position of the defect.

Improved EEMD in the Application of Signal Singularity Detection

2012 ◽  
Vol 518-523 ◽  
pp. 3847-3851
Author(s):  
Mei Jun Zhang ◽  
Chuang Wang ◽  
Hao Chen ◽  
Qun Zhang Tu
Keyword(s):  
Frequency Spectrum ◽  
Original Data ◽  
Singularity Detection ◽  
Time Frequency ◽  
Local Characteristics ◽  
Cross Terms ◽  
Marginal Spectrum ◽  
Frequency Components ◽  
Detection Signal ◽  
Improved Eemd

In order to solve the endpoint effect and modal aliasing phenomenon in EMD and EEMD,Improved EEMD is put forward, and the application in signal singularity detection is researched in this paper. The improved EEMD will signal drops down into a series of different IMF to highlight the different local characteristics of original data, and then calculate Hilbert marginal spectrum and time-frequency spectrum to determine the frequency of these mutations and mutations position. To compared with FT, STFT, WVD,WT, EMD and EEMD etc, No cross-terms and no false IMF components are produced in the Hilbert time-frequency spectrum of the improved EEMD. Different frequency components and frequency mutations position are clearly distinguished at the same time. The Hilbert time-frequency spectrum of the improved EEMD has more superior detection signal singularity ability.

Phase velocity estimation technique based on adaptive beamforming for ultrasonic guided waves propagating along cortical long bones

2017 ◽  
Vol 56 (7S1) ◽  
pp. 07JF06 ◽  
Author(s):  
Shigeaki Okumura ◽  
Vu-Hieu Nguyen ◽  
Hirofumi Taki ◽  
Guillaume Haïat ◽  
Salah Naili ◽  
...  
Keyword(s):  
Phase Velocity ◽  
Guided Waves ◽  
Adaptive Beamforming ◽  
Velocity Estimation ◽  
Ultrasonic Guided Waves ◽  
Long Bones ◽  
Estimation Technique

scholarly journals Warped Wigner-Hough Transform for Defect Reflection Enhancement in Ultrasonic Guided Wave Monitoring

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Luca De Marchi ◽  
Emanuele Baravelli ◽  
Giampaolo Cera ◽  
Nicolò Speciale ◽  
Alessandro Marzani
Keyword(s):  
Hough Transform ◽  
Guided Waves ◽  
Lamb Waves ◽  
Guided Wave ◽  
Nonlinear Signal Processing ◽  
Localization Accuracy ◽  
Time Frequency ◽  
Ultrasonic Guided Wave ◽  
Inspection Systems ◽  
Nonlinear Signal

To improve the defect detectability of Lamb wave inspection systems, the application of nonlinear signal processing was investigated. The approach is based on a Warped Frequency Transform (WFT) to compensate the dispersive behavior of ultrasonic guided waves, followed by a Wigner-Ville time-frequency analysis and the Hough Transform to further improve localization accuracy. As a result, an automatic detection procedure to locate defect-induced reflections was demonstrated and successfully tested by analyzing numerically simulated Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented for real-world structural health monitoring applications.

Non-Gaussian Wave Groups Generated in an Offshore Wave Basin

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Z. Cherneva ◽  
C. Guedes Soares
Keyword(s):  
Gaussian Process ◽  
Frequency Spectrum ◽  
Local Spectrum ◽  
Wave Groups ◽  
High Wave ◽  
Time Frequency ◽  
Wave Basin ◽  
The Mean ◽  
Non Gaussian ◽  
Experimental Runs

The main goal of the present paper is to study the differences of the descriptors of the wave groups in the nonlinear case in comparison with the same parameters for a Gaussian process. The data analyzed are from a deep water basin of Marintek. They consist of sequence of five identical independent experimental runs of unidirectional waves measured at ten fixed points situated in different distances from the wave maker. Each series contain about 1800 waves. Thus the statistics collected from a given gauge comprise about 9000 waves combined in a number of wave groups. Because the series describe a process significantly different from the Gaussian one, an upper and lower envelopes are introduced as lines which connect the peaks of the crests and the lower points of the troughs respectively. Spline functions are applied to calculate these envelopes. Then, the mean high run and mean group length are estimated for different levels, their ensemble average over five experimental runs is found for every gauge and is compared with the results of the theory of Gaussian process. It is found that the values of the mean time intervals of the groups correlate with coefficient of kurtosis of the process. It is determined also that mean group length is shorter and the mean high run is larger for the nonlinear wave groups in comparison with the Gaussian wave groups. The modification of wave groups in space and time is investigated in the work as well. Wigner time-frequency spectrum with Choi-Williams kernel is applied to describe the process of entire modulation and demodulation of the groups. It is found that before formation of the high wave a wave down-shifting takes place. At this stage the local spectrum is relatively narrow and the group shrinks continuously. Close to the focus the time-frequency spectrum is very wide and the group has a triangle form. Further the high wave breaks and the wave group acquires the form of “three sisters.” The transform of the group continues by its disintegration, the local spectrum stands narrow and an up-shifting is observed.

Leak location in gas pipelines using cross-time–frequency spectrum of leakage-induced acoustic vibrations

2014 ◽  
Vol 333 (17) ◽  
pp. 3889-3903 ◽  
Author(s):  
Shuaiyong Li ◽  
Yumei Wen ◽  
Ping Li ◽  
Jin Yang ◽  
Xiaoxuan Dong ◽  
...  
Keyword(s):  
Frequency Spectrum ◽  
Acoustic Vibrations ◽  
Gas Pipelines ◽  
Time Frequency ◽  
Leak Location
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