The Experts below are selected from a list of 1848 Experts worldwide ranked by ideXlab platform
Shiyuan Zhou - One of the best experts on this subject based on the ideXlab platform.
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study of Lamb Wave propagation in plate for unde by 2 d fem model
International Conference on Measuring Technology and Mechatronics Automation, 2010Co-Authors: Hanhui Xu, Chunguang Xu, Shiyuan ZhouAbstract:Ultrasonic nondestructive evaluation (UNDE) of notch defect by Lamb Wave is investigated theoretically and experimentally in this paper. It is hard to predict and explain the received Lamb Signal of UNDE due to its dispersive nature. The width of the notch is available by delay time between reflection Signal and first echo Signal, and its depth can be evaluated by reflection coefficient. A model by FEM (finite element method) has been used to predict reflected Signals by boundaries of defect and the end of the plate. In comparison with the results from the theory and experiment, it is confirmed that FEM is efficient for predicting Lamb Wave Signal propagation and interaction with defect in plate for UNDE.
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Time-Frequency Analysis for Nonlinear Lamb Wave Signal
2009 2nd International Congress on Image and Signal Processing, 2009Co-Authors: Xu Chunguang, Shiyuan ZhouAbstract:Lamb Wave for Ultrasonic Nondestructive Evaluation (UNDE) by its nonlinear effects is investigated theoretically and experimentally with time-frequency analysis. The complication of Lamb Wave propagation due to its dispersive nature makes the received Signal of UNDE hard to explain. Two transducers are employed in pitch-catch way together with a wedge to meet the excitation condition of low order fundamental and second harmonic Lamb Waves. Two time-frequency methods have been used to verify the interaction mechanism between nonlinear Lamb Waves with plate-like structures. The information of group velocity and out-of-plane amplitude of certain order fundamental and second harmonic Lamb Waves is the main means to research the nonlinear effect in this paper. The cumulative effect of second harmonic Lamb Wave is also researched for defect evaluation. In comparison with the results between theory and experiment, it's concluded that the pseudo Wigner-Ville distribution (PWVD) and short-time Fourier transform (STFT) are effective for processing nonlinear Lamb Wave Signal on UNDE.
C R Bijudas - One of the best experts on this subject based on the ideXlab platform.
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time reversed Lamb Wave for damage detection in a stiffened aluminum plate
Smart Materials and Structures, 2013Co-Authors: C R Bijudas, Mira Mitra, P M MujumdarAbstract:According to the concept of time reversibility of the Lamb Wave, in the absence of damage, a Lamb Wave Signal can be reconstructed at the transmitter location if a time reversed Signal is sent back from the receiver location. This property is used for baseline-free damage detection, where the presence of damage breaks down the time reversibility and the mismatch between the reconstructed and the input Signal is inferred as the presence of damage. This paper presents an experimental and a simulation study of baseline-free damage detection in a stiffened aluminum plate by time reversed Lamb Wave (TRLW). In this study, single Lamb Wave mode (A0) is generated and sensed using piezoelectric (PZT) transducers through specific transducer placement and amplitude tuning. Different stiffening configurations such as plane and T-stiffeners are considered. Damage cases of disbonding of stiffeners from the base plate, and vertical and embedded cracks in the stiffened plate, are studied. The results show that TRLW based schemes can efficiently identify the presence of damage in a stiffened plate.
Jing Lin - One of the best experts on this subject based on the ideXlab platform.
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time frequency damage index of broadband Lamb Wave for corrosion inspection
Journal of Sound and Vibration, 2020Co-Authors: Jiadong Hua, Xuwei Cao, Jing LinAbstract:Abstract The method based on Lamb Wave shows great potential for structural health monitoring (SHM) and nondestructive testing (NDT). Damage index (DI) is a series of features extracted from Lamb Wave Signal that can be linked with damage, which can serve as an indicator to depict the damage. Conventional DIs including time-of-flight, amplitude change and Signal difference coefficient are extracted from narrowband Lamb Wave. However, time-of-flight needs prior knowledge of accurate propagation distance, amplitude change and Signal difference coefficient rely on the collection of reference Signals in undamaged condition. To overcome these limitations, different DIs are established from time-frequency distribution of broadband Lamb Wave, which contains rich interaction information between structural feature and various modes over a large frequency range. In particular, three DIs including ridge curvature, energy distribution ratio and image difference coefficient, are extracted from Lamb Wave time-frequency images and employed in probability imaging algorithm for damage localization. An experiment is given to validate the effectiveness of established time-frequency DIs.
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mode identification and extraction of broadband ultrasonic guided Waves
Measurement Science and Technology, 2014Co-Authors: Ming Zhao, Liang Zeng, Jing LinAbstract:Lamb Waves have dispersion and multimodal characteristics, which are the major reasons for the complexity of their Signals. A Signal processing technique is established to extract individual dispersive Waveforms from raw received Lamb Wave Signals, even when they interfere with each other in the time-frequency domain. In this technique, the prior knowledge of the dispersion characteristic is utilized for mode identification. On this basis, the propagation distances of concerned modes are estimated and ridge tracking is completed in the interfered neighboring area. Subsequently, an effective time-varying filter, the Vold-Kalman filter, is introduced to isolate these interfered Wave modes. When each mode is extracted from the overall Lamb Wave Signal, accurate quantitative data on propagation characteristics such as energy, attenuation, amplitude, and reflection coefficients can be accurately estimated. The results illustrate a strategy for optimal design of Lamb Wave inspections in either a pulse-echo or pitch-catch configuration.
Wei Zhao - One of the best experts on this subject based on the ideXlab platform.
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sparse reconstruction based time frequency representation for time of flight extraction of undersampled Lamb Wave Signal
Conference on Precision Electromagnetic Measurements, 2020Co-Authors: Zhe Wang, Songling Huang, Shen Wang, Qing Wang, Wei ZhaoAbstract:Lamb Wave has received considerable attention for inspecting defects. However, the undersampling might occur and lead to the incomplete Signal samples. This paper proposes the sparse reconstruction based method to extract the time-of-flight (TOF) in undersampled Lamb Wave Signal. The sparsity of time-frequency representation (TFR) is utilized to build the sparse reconstruction model and the orthogonal matching pursuit is applied to solve this model. The TOF is calculated according to the time-frequency information in the TFR. The method is implemented on simulated Lamb Wave Signal and the relative error of TOF is 1.48 %. The results demonstrate that the accurate TOF is obtained in undersampled situation.
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mode identification of broadband Lamb Wave Signal with squeezed Wavelet transform
Applied Acoustics, 2017Co-Authors: Shen Wang, Songling Huang, Qing Wang, Yu Zhang, Wei ZhaoAbstract:Multiple Wave modes often exist in the ultrasonic guided Waves simultaneously, and these modes are dispersive, so the guided Wave Signals are very complex, even for the relatively simple situation of a narrowband excitation. The guided Wave Signals are even more difficult to analyze for broadband excitations. Time-frequency representations are appropriate for the analysis of the guided Wave Signals considering their non-stationary and transient nature. As a post-processing tool, the squeezed Wavelet transform is studied for broadband Lamb Wave mode identification in this work. The influence of the parameters of the Gabor mother Wavelet on the performance of the transform is analyzed in details. It is found that the product of the σ parameter of the used Gauss function and the center frequency ω0 of the Wavelet decides the overall time and frequency resolutions, so a proper selection of the value of this product σω0 is crucial for the squeezed Wavelet transform. The squeezed Wavelet transform is first applied to the analysis of a synthesized Signal for verification. Then it’s applied for mode identification of a simulated broadband Lamb Wave Signal. By traversing the value of σω0, a roughly optimum analysis performance is achieved for the squeezed Wavelet transform for the case of σω0=11, where the modes are well separated and the interferences between the modes are minimal. It’s proved that as an alternative tool, the squeezed Wavelet transform could be used for the analysis of a broadband Lamb Wave Signal. An additional benefit of this transform is that it permits reconstruction of the original Signal or its components, which is not possible for the reassigned scalogram.
Alessandro Marzani - One of the best experts on this subject based on the ideXlab platform.
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a Signal processing approach to exploit chirp excitation in Lamb Wave defect detection and localization procedures
Mechanical Systems and Signal Processing, 2013Co-Authors: Luca De Marchi, Alessandro Perelli, Alessandro MarzaniAbstract:A non-linear Lamb Wave Signal processing strategy aimed at extending the capability of active–passive networks of PZT transducers for defect detection is proposed. In particular, the proposed Signal processing allows to use chirp shaped pulses in actuation, instead of classically applied spiky pulses, requiring thus lower input voltages. To such aim, the acquired Lamb Waves are processed by means of a two-step procedure: a warped frequency transform (WFT) to compensate for the dispersion due to the traveled distance, followed by a compression procedure to remove from the Signals the induced chirp frequency modulation. Next, the resulting Signals are exploited to feed an imaging algorithm aimed at providing the position of the defect on the plate. The potential of the procedure is demonstrated and validated by analyzing experimental Lamb Waves propagating in an aluminum plate where defects were emulated by posing an added mass on the plate. The proposed automatic procedure is suitable to locate defect-induced reflections and can be easily implemented in real applications for structural health monitoring.
