scholarly journals Research on Leakage Location of Spacecraft in Orbit Based on Frequency Weighting Matrix Beamforming Algorithm by Lamb Waves

2020 ◽  
Vol 10 (4) ◽  
pp. 1201 ◽  
Author(s):  
Lei Qi ◽  
Zhoumo Zeng ◽  
Yu Zhang ◽  
Lichen Sun ◽  
Xiaobo Rui ◽  
...  
Keyword(s):  
Sensor Array ◽  
Lamb Waves ◽  
Wave Dispersion ◽  
Weighting Method ◽  
Wave Speeds ◽  
Frequency Bands ◽  
Weighting Matrix ◽  
Acoustic Emission Sensors ◽  
Frequency Weighting ◽  
Beamforming Algorithm

Clashes between space debris and spacecraft in orbit may cause air leakages, which pose a substantial danger to the crew and the spacecraft. Lamb wave dispersion in spacecraft structures and the randomness of leak holes are the difficulties in leak location. To solve these problems, a frequency weighting matrix beamforming algorithm is proposed in this paper. The elastic Lamb waves that are caused by leakages are acquired by an ‘L’ shaped sensor array consisting of eight acoustic emission sensors. The angle of a leak can be obtained through the superposition of different time delays, and the intersection of two angles can be used to find the location of the leak. Traditional beamforming is improved by matching the wave speeds in different frequency bands and weightings according to the energy distribution. Narrowband filtering is used to delay overlay different signal speeds with different frequency bands via a dispersion curve. The weighting method is used to compensate the frequency band response of different leak holes. The detailed location algorithm process is introduced and verified by experiments. For 1.5 and 2 mm leak holes, location direction accuracies of 1.33° and 1.93° for one sensor array were obtained, respectively.

scholarly journals Dispersion analysis of Lamb waves with narrow frequency bands

2008 ◽  
Vol 57 (7) ◽  
pp. 4265
Author(s):  
Li Fu-Cai ◽  
Meng Guang
Keyword(s):  
Lamb Waves ◽  
Dispersion Analysis ◽  
Frequency Bands

Determination of Vibration Source Locations in Laminated Composite Plates Using Lamb Wave Analysis

2010 ◽  
Vol 123-125 ◽  
pp. 899-902
Author(s):  
Chao Du ◽  
Qing Qing Ni ◽  
Toshiaki Natsuki
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Laminated Composite ◽  
Composite Plates ◽  
Wave Dispersion ◽  
Laminated Plates ◽  
Vibration Source ◽  
Arrival Times ◽  
Wave Velocities

Signals propagate on plate-like structures as ultrasonic guided waves, and analysis of Lamb waves has been widely used for on-line monitoring. In this study, the wave velocities of symmetric and anti-symmetric modes in various directions of propagation were investigated. Since the wave velocities of these two modes are different, it is possible to compute the difference in their arrival times when these waves propagated the distance from the vibration source to sensor. This paper presents an evaluation formulation of wave velocity and describes a generalized algorithm for locating a vibration source on a thin, laminated plate. With the different velocities of two modes based on Lamb wave dispersion, the method uses two sensors to locate the source on a semi-infinite interval of a plate. The experimental procedure supporting this method employs pencil lead breaks to simulate vibration sources on quasi-isotropic and unidirectional laminated plates. The transient signals generated in this way are transformed using a wavelet transform. The vibration source locations are then detected by utilizing the distinct wave velocities and arrival times of the symmetric and anti-symmetric wave modes. The method is an effective technique for identifying impact locations on plate-like structures.

Experimental Validation of Dispersion Curves in Plates for Acoustic Emission

2006 ◽  
Vol 13-14 ◽  
pp. 53-60
Author(s):  
Rhys Pullin ◽  
Pete T. Theobald ◽  
Karen M. Holford ◽  
S.L. Evans
Keyword(s):  
Acoustic Emission ◽  
Lamb Wave ◽  
Arrival Times ◽  
Wave Speeds ◽  
Lead Fracture ◽  
Acoustic Emission Sensors ◽  
Broadband Pulse ◽  
Thick Steel ◽  
Ae Signals ◽  
Wave Modes

This paper presents the findings of an investigation to determine theoretically and empirically the wave speeds and frequency content of the two primary Lamb wave modes, the symmetric (S0) and anti-symmetric (A0). A 2 mm thick steel plate measuring 700 mm by 700 mm was used to perform all measurements. A broadband pulse propagated through the plate and detected by a conical type piezoelectric receiver was used to show how the dispersive properties of the plate influenced the detected AE signals. It was shown that the two primary Lamb wave modes cover a very broad range of velocities, leading to a severe spreading of arrival times. A further investigation was completed using four acoustic emission sensors to record a pencil lead fracture, which was used as an artificial source. Reflections in the plate were shown to cause interference in the signal that can complicate the interpretation of the arrival modes. A recorded signal 400mm from the source was filtered into frequency bands. The arrival times of the wave modes were determined for each frequency band and the appropriate velocities calculated allowing a dispersion curve to be plotted experimentally. The plotted curve was shown to be a very close approximate to the calculated curve.

Dispersion in Nonlinear Plates: Amplitude Dependent Lamb Waves

2016 ◽  
Author(s):  
Pawel Packo ◽  
Michael J. Leamy
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Dispersion ◽  
Inner Product ◽  
Solvability Conditions ◽  
Higher Harmonic Generation ◽  
Wave Technique ◽  
Lamb Wave Propagation ◽  
Higher Order Dispersion ◽  
Adjoint Solutions

This paper presents results from a perturbation-based analysis approach, and accompanying numerical validation, for calculating amplitude-dependent Lamb wave dispersion in nonlinear plates. Nonlinearities considered include those arising from geometric and material nonlinearities. Using a Lindstedt-Poincaré perturbation analysis, nonlinear dispersion relationships are presented in closed form using the partial wave technique. Solvability conditions, based on an operator formalism accompanied by inner product projections against adjoint solutions, yield higher-order dispersion approximations capturing amplitude-dependent Lamb wave propagation. Numerical simulations using a cellular automata approach verify the predicted dispersion shifts for an example nonlinear plate. The analysis and identification of amplitude-dependent, nonlinear Lamb wave dispersion complements recent research focusing on higher harmonic generation and internally resonant waves, which require precise frequency-wavenumber matching, including at large amplitudes.

scholarly journals Ultrasound Defect Localization in Shell Structures with Lamb Waves Using Spare Sensor Array and Orthogonal Matching Pursuit Decomposition

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 8127
Author(s):  
Weilei Mu ◽  
Yuqing Gao ◽  
Guijie Liu
Keyword(s):  
Sensor Array ◽  
Lamb Waves ◽  
Matching Pursuit ◽  
Wave Packets ◽  
Piezoelectric Transducers ◽  
Orthogonal Matching Pursuit ◽  
Dispersion Effects ◽  
Resolution Improvement ◽  
Matching Pursuit Decomposition ◽  
Dispersion Part

Lamb waves have multimodal and dispersion effects, which reduces their performance in damage localization with respect to resolution. To detect damage with fewest sensors and high resolution, a method, using only two piezoelectric transducers and based on orthogonal matching pursuit (OMP) decomposition, was proposed. First, an OMP-based decomposition and dispersion removal algorithm is introduced, which is capable of separating wave packets of different propagation paths and removing the dispersion part successively. Then, two simulation signals, with nonoverlapped and overlapped wave packets, are employed to verify the proposed method. Thereafter, with the proposed algorithm, the wave packets reflected from the defect and edge are all separated. Finally, a sparse sensor array with only two transducers succeeds in localizing the defect. The experimental results show that the OMP-based algorithm is beneficial for resolution improvement and transducer usage reduction.

scholarly journals A Gas Leakage Localization Method Based on a Virtual Ultrasonic Sensor Array

Sensors ◽  
2019 ◽  
Vol 19 (14) ◽  
pp. 3152 ◽  
Author(s):  
Lei Li ◽  
Kuan Yang ◽  
Xiaoyu Bian ◽  
Qinghui Liu ◽  
Yizhuo Yang ◽  
...  
Keyword(s):  
Sensor Array ◽  
Phased Array ◽  
Ultrasonic Sensor ◽  
Leakage Detection ◽  
Localization Technique ◽  
Localization Method ◽  
Gas Leakage ◽  
Virtual Array ◽  
Beamforming Algorithm ◽  
Cross Power Spectrum

In traditional sensory array-based acoustic emission methods that are used for gas leakage localization, the localization resolution depends on the spatial aperture of the array, that is, the number of sensors. Most of the existing methods use small arrays that can only achieve low-resolution localization results because of limitations such as the amplitude and phase consistency, the complexity and cost of the system. This paper reports the first application of a virtual phased array for gas leakage detection to obtain high-resolution localization results. This method uses a virtual linear ultrasonic sensor array composed of only two sensors to acquire leakage signals. Then, we use the virtual beamforming algorithm based on the cross-power spectrum to estimate the location of the leakage source. Several experiments were conducted to evaluate the effectiveness and operability of the proposed method. The impacts of various factors on the performance of the localization technique are compared and discussed, including factors such as the number of sensors and the distance between the leak hole and virtual array. The results demonstrate that the proposed method accurately and reliably localizes gas leakages.

scholarly journals Fully Noncontact Wave Propagation Imaging in an Immersed Metallic Plate with a Crack

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jung-Ryul Lee ◽  
Jae-Kyeong Jang ◽  
Cheol-Won Kong
Keyword(s):  
Wave Propagation ◽  
Lamb Wave ◽  
Continuous Wave ◽  
Imaging System ◽  
Lamb Waves ◽  
Laser Doppler Vibrometer ◽  
Wave Dispersion ◽  
Wave Mode ◽  
Dispersion Curves ◽  
Guided Wave

This study presents a noncontact sensing technique with ultrasonic wave propagation imaging algorithm, for damage visualization of liquid-immersed structures. An aluminum plate specimen (400 mm × 400 mm × 3 mm) with a 12 mm slit was immersed in water and in glycerin. A 532 nm Q-switched continuous wave laser is used at an energy level of 1.2 mJ to scan an area of 100 mm × 100 mm. A laser Doppler vibrometer is used as a noncontact ultrasonic sensor, which measures guided wave displacement at a fixed point. The tests are performed with two different cases of specimen: without water and filled with water and with glycerin. Lamb wave dispersion curves for the respective cases are calculated, to investigate the velocity-frequency relationship of each wave mode. Experimental propagation velocities of Lamb waves for different cases are compared with the theoretical dispersion curves. This study shows that the dispersion and attenuation of the Lamb wave is affected by the surrounding liquid, and the comparative experimental results are presented to verify it. In addition, it is demonstrated that the developed fully noncontact ultrasonic propagation imaging system is capable of damage sizing in submerged structures.

scholarly journals Fluids Alter Elasticity Measurements: Porous Wave Propagation Accounts for Shear Wave Dispersion in Elastography

2021 ◽  
Vol 9 ◽  
Author(s):  
Johannes Aichele ◽  
Stefan Catheline
Keyword(s):  
Wave Propagation ◽  
Elastic Wave ◽  
Shear Wave ◽  
Wave Dispersion ◽  
Elastic Wave Propagation ◽  
Elastic Model ◽  
Fluid Viscosity ◽  
Wave Speeds ◽  
Wide Range

In shear wave elastography, rotational wave speeds are converted to elasticity measures using elastodynamic theory. The method has a wide range of applications and is the gold standard for non-invasive liver fibrosis detection. However, the observed shear wave dispersion of in vivo human liver shows a mismatch with purely elastic and visco-elastic wave propagation theory. In a laboratory phantom experiment we demonstrate that porosity and fluid viscosity need to be considered to properly convert shear wave speeds to elasticity in soft porous materials. We extend this conclusion to the clinical application of liver stiffness characterization by revisiting in vivo studies of liver elastography. To that end we compare Biot’s theory of poro-visco-elastic wave propagation to Voigt’s visco-elastic model. Our results suggest that accounting for dispersion due to fluid viscosity could improve shear wave imaging in the liver and other highly vascularized organs.

A Point-Focus PVDF Transducer for Lamb Wave Measurements

2002 ◽  
Vol 18 (1) ◽  
pp. 29-33
Author(s):  
Yung-Chun Lee ◽  
Yi Fan Tein ◽  
Yu Yi Chao
Keyword(s):  
Lamb Wave ◽  
Acoustic Waves ◽  
Lamb Waves ◽  
Experimental Testing ◽  
Spherical Shape ◽  
Wave Dispersion ◽  
Dispersion Curves ◽  
Pvdf Film ◽  
Wave Measurements ◽  
Metal Plates

ABSTRACTThis paper reports the development of a point-focused PVDF transducer with a large aperture surface and its application on measuring Lamb wave dispersion curves. The point-focused transducer is constructed by forcing a piezoelectric PVDF film into a concave spherical shape. The acoustic waves radiated from the PVDF film are then focused into a point without using any acoustic lens. Similar to its line-focused counterpart, the point-focused transducer is capable of measuring dispersion curves of lamb waves provided its aperture angle is large enough. To verify this, experimental testing is carried out on several thin metal plates and good measurement results are observed. Future improvements and applications on the transducer will be addressed.

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