Evaluation of complex spectrum of the symmetrical Lamb waves for three-layered plates at low frequency. Part II: Asymptotics/numerical results

2019 ◽  
Vol 230 ◽  
pp. 111428 ◽  
Author(s):  
D.D. Zakharov ◽  
A.V. Nikonov
Keyword(s):  
Lamb Waves ◽  
Low Frequency ◽  
Numerical Results ◽  
Complex Spectrum ◽  
Layered Plates

Localization of Fatigue Cracks Using Low-Frequency Nonlinear Lamb Waves in Numerical Perspective

2018 ◽  
Author(s):  
Jichao Xu ◽  
Nuoke Wei ◽  
Wujun Zhu ◽  
Yanxun Xiang ◽  
Fuzhen Xuan ◽  
...  
Keyword(s):  
Lamb Waves ◽  
Fatigue Cracks ◽  
Low Frequency

Non-Destructive Evaluation of a Delamination in Laminates by Lamb Wave Propagation

2007 ◽  
Vol 353-358 ◽  
pp. 2345-2348
Author(s):  
Zheng Hua Qian ◽  
Feng Jin ◽  
Zi Kun Wang ◽  
Kikuo Kishimoto
Keyword(s):  
Lamb Waves ◽  
Low Frequency ◽  
Relative Location ◽  
Laminated Plate ◽  
Non Destructive Evaluation ◽  
Symmetric Plane ◽  
Expansion Coefficients ◽  
Relative Errors ◽  
Lamb Wave Propagation ◽  
Non Destructive

The diffraction of Lamb waves by a finite delamination situated on a random plane parallel to the symmetric plane of a laminated plate is taken into account. Two imaginary planes are introduced to solve the problem by adopting the method of mode matching. By taking an appropriate finite number of terms of the infinite expansion series and some selected points on the two imaginary planes through convergence and precision tests, a matrix equation is obtained to evaluate the expansion coefficients numerically. Reflection coefficients versus the normalized length a/h and the relative location h1/h of the delamination are calculated in the low-frequency domain, the relative errors are found to be less than 1%. Results obtained indicate that the theory developed in this paper is meaningful for the detection of both the size and the location of a delamination in a laminated plate by cooperating with experimental techniques for the non-destructive evaluation (NDE) technology.

Forecasting Subcritical and Supercritical Flutter Using Gust Responses

2015 ◽  
Author(s):  
Amin Ghadami ◽  
Bogdan I. Epureanu
Keyword(s):  
Dynamical Systems ◽  
Prediction Accuracy ◽  
Low Frequency ◽  
Numerical Results ◽  
Hopf Bifurcations ◽  
Aeroelastic System ◽  
New Techniques ◽  
Low Frequency Oscillations ◽  
Unique Method ◽  
Gust Loads

This work presents a unique method to forecast flutter (Hopf) bifurcations based on observations of the system only in the pre-bifurcation regime. New techniques are introduced in to enhance prediction accuracy for both low-frequency oscillations and large-dimensional dynamical systems. The method is applied to an aeroelastic system using its response to gust loads. Numerical results demonstrate that the method can predict the post-bifurcation regime accurately for both supercritical and subcritical flutter.

Complex spectrum analyzer of low-frequency periodic signals

1983 ◽  
Vol 26 (8) ◽  
pp. 674-677
Author(s):  
Yu. K. Rybin ◽  
V. P. Budeikin
Keyword(s):  
Low Frequency ◽  
Spectrum Analyzer ◽  
Complex Spectrum ◽  
Periodic Signals

Active sensing of impact damage in composite sandwich panels by low frequency Lamb waves

2008 ◽  
Vol 112 (1131) ◽  
pp. 279-283 ◽  
Author(s):  
C. Soutis ◽  
K. Diamanti
Keyword(s):  
Lamb Waves ◽  
Impact Damage ◽  
Low Frequency ◽  
Practical Applications ◽  
Reinforced Plastics ◽  
Composite Sandwich ◽  
Composite Sandwich Structures ◽  
Inspection Strategy ◽  
Extent Of Damage ◽  
Non Destructive

Abstract The development of a robust non-destructive system to detect and monitor the extent of damage in carbon fibre reinforced plastics (CFRP) during service life is a key problem in many practical applications, especially in the aircraft industry. The lack of such technique has severely limited the potentially extensive use of composite materials. In this study a cost and time effective inspection strategy for in-service health monitoring of composites is demonstrated using the fundamental anti-symmetric A 0 Lamb mode at frequencies of 15-20kHz. In principle, this method involves analysis of the transmitted and/or reflected wave after interacting with the test-piece boundaries or discontinuities (defects). In the present work, the applicability of the technique to composite sandwich structures is explored and defects of critical size are successfully detected.

scholarly journals Core–skin debonding detection in honeycomb sandwich structures through guided wave wavefield analysis

2018 ◽  
Vol 30 (9) ◽  
pp. 1306-1317 ◽  
Author(s):  
Lingyu Yu ◽  
Zhenhua Tian ◽  
Xiaopeng Li ◽  
Rui Zhu ◽  
Guoliang Huang
Keyword(s):  
Guided Waves ◽  
Sandwich Structures ◽  
Lamb Waves ◽  
Laser Doppler Vibrometer ◽  
Low Frequency ◽  
Guided Wave ◽  
Honeycomb Sandwich ◽  
Debonding Detection ◽  
The Waves ◽  
Detection And Quantification

Ultrasonic guided waves have proven to be an effective and efficient method for damage detection and quantification in various plate-like structures. In honeycomb sandwich structures, wave propagation and interaction with typical defects such as hidden debonding damage are complicated; hence, the detection of defects using guided waves remains a challenging problem. The work presented in this article investigates the interaction of low-frequency guided waves with core–skin debonding damage in aluminum core honeycomb sandwich structures using finite element simulations. Due to debonding damage, the waves propagating in the debonded skin panel change to fundamental antisymmetric Lamb waves with different wavenumber values. Exploiting this mechanism, experimental inspection using a non-contact laser Doppler vibrometer was performed to acquire wavefield data from pristine and debonded structures. The data were then processed and analyzed with two wavefield data–based imaging approaches, the filter reconstruction imaging and the spatial wavenumber imaging. Both approaches can clearly indicate the presence, location, and size of the debonding in the structures, thus proving to be effective methods for debonding detection and quantification for honeycomb sandwich structures.

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