A Method of Dispersion Compensation Based on Warped Frequency Transform

2013 ◽  
Vol 718-720 ◽  
pp. 2062-2067 ◽  
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.

Noncontact Evaluation of Defects in Thin Plate With Multimodes Lamb’s Waves and Wavelet Transform

2002 ◽  
Author(s):  
Morimasa Murase ◽  
Koichiro Kawashima
Keyword(s):  
Group Velocity ◽  
Thin Plate ◽  
Wavelet Transformation ◽  
Velocity Dispersion ◽  
Lamb Waves ◽  
Group Velocity Dispersion ◽  
Dispersion Curves ◽  
Contact Method ◽  
Intact Specimen ◽  
Time Frequency

Multimode’s Lamb waves in aluminum plates with various defects were excited by a Q-switched Nd:YAG laser. The Lamb waves past through the defects were received a laser interferometer. The received signals of the Lamb waves are processed by the wavelet transformation. The wavelet transformation is generally shown on the time-frequency domain. By dividing a propagation distance by the time, the group velocities are identified. In this way, group velocity dispersion maps of multimode’s Lamb waves are constructed with the received temporal signals. By changing the shape of the mother wavelet, Gabor function, we can identify the dispersion curves of the higher mode Lamb waves. The group velocity dispersion maps of a intact specimen agree well on theoretical dispersion curves of S0, A0, S1, A1, S2, A2, and A3 modes. The difference between the dispersion maps of the intact specimen and that with defects clearly visualizes the existence of defects. This non-contact method is effective for inspecting various defects in thin plate structures.

Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation

2007 ◽  
Vol 32 (14) ◽  
pp. 2025 ◽  
Author(s):  
I. Zeylikovich ◽  
H. I. Sztul ◽  
V. Kartazaev ◽  
T. Le ◽  
R. R. Alfano
Keyword(s):  
Group Velocity ◽  
Velocity Dispersion ◽  
Group Velocity Dispersion ◽  
Dispersion Compensation

scholarly journals A fast decoupled ISAR high-resolution imaging method using structural sparse information under low SNR

2019 ◽  
Vol 30 (03) ◽  
pp. 492-503
Author(s):  
Long Xiang ◽  
◽  
Shaodong Li ◽  
Jun Yang ◽  
Wenfang Chen ◽  
...  
Keyword(s):  
High Resolution ◽  
Imaging Method ◽  
High Resolution Imaging ◽  
Low Snr ◽  
Resolution Imaging

The Curved Plate Flaw's Location and Direction Detecting Based on the Transducer Array

2013 ◽  
Vol 389 ◽  
pp. 223-230
Author(s):  
Xi Peng Li ◽  
Chun Guang Xu ◽  
Zhao Liu ◽  
Han Hui Xu
Keyword(s):  
Phase Velocity ◽  
Elastic Wave ◽  
Wave Equations ◽  
Velocity Dispersion ◽  
Imaging Method ◽  
Finite Element Software ◽  
Phase Velocity Dispersion ◽  
Elastic Wave Equations ◽  
The Relationship ◽  
Detecting Method

The curved structural plate components have been widely used in petroleum, natural gas, chemical industry, and other industries fields, monitoring and detecting the curved structural plate components flaw has a great significance for improving the components integrity, reliability and lifespan in service. Based on the elastic wave fundamental theory, elastic wave equations, and phase velocity dispersion characteristic curves in curved plate component, the article gives the phase velocity practical detecting method. By using thecomsolfinite element software, the author proposed a wave propagating forward modeling analytical method, which gives a guidance to study the relationship between the wave and the flaw. By adopting the ellipse algorithm, the article proposed a positioning and imaging method which was used to locate the flaws position and distinguish the flaws direction. Based on the theoretical and technical analysis above, a number of experiments has been done, and the results shows that the detecting and imaging method can locate and image the flaws position and its geometrical morphology precisely for the curved plates flaw detecting.

A time reversal damage imaging method for structure health monitoring using Lamb waves

2010 ◽  
Vol 19 (11) ◽  
pp. 114301 ◽  
Author(s):  
Hai-Yan Zhang ◽  
Ya-Ping Cao ◽  
Xiu-Li Sun ◽  
Xian-Hua Chen ◽  
Jian-Bo Yu
Keyword(s):  
Health Monitoring ◽  
Time Reversal ◽  
Lamb Waves ◽  
Imaging Method ◽  
Structure Health Monitoring ◽  
Damage Imaging

scholarly journals Fast high-resolution imaging method for wide-band rotating targets

2019 ◽  
Vol 2019 (20) ◽  
pp. 6987-6990
Author(s):  
Hu Xiang ◽  
Shaodong Li ◽  
Long Xiang ◽  
Wenfeng Chen ◽  
Jun Yang
Keyword(s):  
High Resolution ◽  
Wide Band ◽  
Imaging Method ◽  
High Resolution Imaging ◽  
Resolution Imaging
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