scholarly journals Full-field localization of plate-thickness inhomogeneities through the local changes in the wavenumber of Lamb waves measured with pulsed TV holography

2008 ◽  
Author(s):  
J. Luis Deán ◽  
Cristina Trillo ◽  
Ángel F. Doval ◽  
José L. Fernández
Keyword(s):  
Lamb Waves ◽  
Plate Thickness ◽  
Full Field ◽  
Field Localization

Modes of Wave Propagation and Dispersion Relations in Inclusion Reinforced Composite Plates

2010 ◽  
Author(s):  
Yu Cheng Liu ◽  
Jin Huang Huang
Keyword(s):  
Composite Plate ◽  
Elastic Moduli ◽  
Lamb Waves ◽  
Plate Thickness ◽  
Composite Plates ◽  
Dispersion Relations ◽  
Elastic Behavior ◽  
Effective Elastic Moduli ◽  
Aspect Ratios ◽  
Reinforced Composite

This paper mainly analyzes the wave dispersion relations and associated modal pattens in the inclusion-reinforced composite plates including the effect of inclusion shapes, inclusion contents, inclusion elastic constants, and plate thickness. The shape of inclusion is modeled as spheroid that enables the composite reinforcement geometrical configurations ranging from sphere to short and continuous fiber. Using the Mori-Tanaka mean-field theory, the effective elastic moduli which are able to elucidate the effect of inclusion’s shape, stiffness, and volume fraction on the composite’s anisotropic elastic behavior can be predicted explicitly. Then, the dispersion relations and the modal patterns of Lamb waves determined from the effective elastic moduli can be obtained by using the dynamic stiffness matrix method. Numerical simulations have been given for the various inclusion types and the resulting dispersions in various wave types on the composite plate. The types (symmetric or antisymmetric) of Lamb waves in an isotropic plate can be classified according to the wave motions about the midplane of the plate. For an orthotropic composite plate, it can also be classified as either symmetric or antisymmetric waves by analyzing the dispersion curves and inspecting the calculated modal patterns. It is also found that the inclusion contents, aspect ratios and plate thickness affect propagation velocities, higher-order mode cutoff frequencies, and modal patterns.

Visco-elastic material characterization by means of full field Lamb waves

2021 ◽  
Vol 150 (4) ◽  
pp. A187-A187
Author(s):  
Adil H. Orta ◽  
Joost Segers ◽  
Nicolaas B. Roozen ◽  
Wim Van Paepegem ◽  
Mathias Kersemans ◽  
...  
Keyword(s):  
Elastic Material ◽  
Material Characterization ◽  
Lamb Waves ◽  
Full Field

Simulation of Lamb Wave Propagation Using Excitation Potentials

2017 ◽  
Author(s):  
Mohammad Faisal Haider ◽  
Victor Giurgiutiu ◽  
Bin Lin ◽  
Lingyu Yu
Keyword(s):  
Elastic Waves ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Plate Thickness ◽  
Signal Amplitude ◽  
Pressure Potential ◽  
Theoretical Formulation ◽  
Damage Process ◽  
Plane Displacement ◽  
Wave Modes

Acoustic emission (AE) can be used to measure energy associated with inelastic deformation such as slip, twinning, and microcracking, etc. in a structure. By obtaining AE information during a damage process, the failure indication can be detected. Therefore, better understanding of AE from a damage process is essential for proper damage detection. Elastic waves emission from a damage process due to energy release can be generalized by excitation potentials. There are two types of potentials exists in a plate for straight crested Lamb waves: pressure potential and shear potential. Theoretical formulation showed that due to excitation potentials the elastic waves in a plate followed the Raleigh-Lamb wave equation. The total energy released from damage can be decomposed as pressure potential and shear potential. Each potential has contribution to different wave modes. A numerical simulation was conducted to identify different wave modes due to excitation potentials. Out of plane displacement was calculated numerically on top of the plate at 500 mm distance from excitation point in each of 2mm, 6mm and 12 mm thick stainless steel plate. There were large losses in peak signal amplitude of anti-symmetric fundamental mode (A0) with increasing plate thickness from 2mm to 12 mm.

Propagation of Lamb Waves in Phononic-Crystal Plates

2007 ◽  
Vol 23 (3) ◽  
pp. 223-228 ◽  
Author(s):  
J.-C. Hsu ◽  
T.-T. Wu
Keyword(s):  
Band Gap ◽  
Triangular Lattice ◽  
Lamb Waves ◽  
Phononic Crystal ◽  
Plate Thickness ◽  
Expansion Method ◽  
Band Gaps ◽  
Square Lattice ◽  
Pass Band ◽  
Band Structures

AbstractIn this paper, the band structures of Lamb waves in the two-dimensional phononic-crystal plates are calculated and analyzed based on the plane wave expansion method. The phononic-crystal plates are composed of an array of circular crystalline iron cylinders embedded in the epoxy matrix. Square lattice and triangular lattice are analyzed and discussed, respectively. For the square lattice, two complete band gaps exist, and a narrow pass band between the complete band gaps separates them apart. For the triangular lattice, a wide complete band gap existing with the ratio of gap width to midgap frequency Δω/ωm equal to 72% is found. Furthermore, the influence of the plate thickness is crucial for band structures of Lamb waves. Tuning plate thickness can shift the pass bands effectively, and band shifting causes the variation of the width of complete band gap and its opening and closure.

scholarly journals Numerical solution of Rayleigh-Lamb frequency equation for real, imaginary and complex wavenumbers

2018 ◽  
Vol 157 ◽  
pp. 08011 ◽  
Author(s):  
Michal Šofer ◽  
Petr Ferfecki ◽  
Pavel Šofer
Keyword(s):  
Numerical Solution ◽  
Guided Waves ◽  
Lamb Waves ◽  
Plate Thickness ◽  
Ultrasonic Inspection ◽  
Wave Mode ◽  
Frequency Equation ◽  
Frequency Interval ◽  
Large Structures ◽  
Complete Procedure

Guided waves, especially Lamb waves or shear-horizontal waves, are widely used types of waves for ultrasonic inspection of large structures. Well known property of guided waves is their dispersive character, which means that the propagation velocity of the particular wave mode is not only a function of physical properties of the material, in which the wave propagates or the wave´s frequency, but also depends on the geometry of the structure in itself. Dispersion curves provide us the information related to the dependency between the wavenumber and the frequency of the particular mode and can be obtained by a numerical solution of Rayleigh-Lamb frequency equation. A solution of Rayleigh-Lamb frequency equation forms for a given frequency and plate thickness a set of a finite number of real and pure imaginary wavenumbers and an infinite number of complex wavenumbers. Proposed paper presents a complete procedure of how to obtain all three kinds of wavenumbers for a given geometry and frequency interval. The main emphasis is placed on the effectiveness of the procedures, which are used for finding the roots of dispersion equation for all three kinds of wavenumbers.

Band Gaps of Lamb Waves Propagating in One-Dimensional Different Quasi-Periodic Composite Thin Plates

2012 ◽  
Vol 160 ◽  
pp. 175-179
Author(s):  
Jian Gao ◽  
Min Zhao ◽  
Ya Zhuo Xie ◽  
Xing Gan Zhang
Keyword(s):  
Lamb Waves ◽  
Plate Thickness ◽  
Physical Property ◽  
Composite Plates ◽  
Band Gaps ◽  
Thin Plates ◽  
Periodic Sequences ◽  
One Dimensional ◽  
Periodic Composite ◽  
Periodic Models

We present a comparative study on band-gap structures of Lamb waves propagating in one-dimensional quasi-periodic composite thin plates, which are composed of different quasi-periodic models such as Cantor, Fibonacci, Thue-Morse, and Double periodic sequences, respectively. The transmitted power spectra (TPS) of the transient Lamb waves propagating in composite plates is calculated numerically by employing the finite element method. By comparing among TPS in different plates with the different ratios of the plate thickness to the lattice spacing, it is found that different quasi-periodic models present different behavior of the split-up of band gaps. Our works are significant not only for understanding intrinsic physical property of the quasi-periodic sequences, but also for designing the special structures of quasi-periodic arrays to adjust the width of band gaps and the frequency ranges of phononic crystals in applications.

Simulation of Interaction Between Lamb Waves and Cracks for Structural Health Monitoring With Piezoelectric Wafer Active Sensors

2012 ◽  
Author(s):  
Yanfeng Shen ◽  
Victor Giurgiutiu
Keyword(s):  
Lamb Waves ◽  
Mode Conversion ◽  
Amplitude Ratio ◽  
Second Harmonic ◽  
Plate Thickness ◽  
Excitation Frequency ◽  
Damage Index ◽  
Spectral Amplitude ◽  
Breathing Crack ◽  
Piezoelectric Wafer

In this paper, the detection for two kinds of cracks is studied: (1) linear notch crack; (2) nonlinear breathing crack. A pitch-catch method with piezoelectric wafer actives sensors (PWAS) is used to interrogate an aluminum plate with a linear notch crack and a nonlinear breathing crack respectively as two cases. The inspection Lamb waves generated by the transmitter PWAS, propagate into the structure, interact with the crack, acquire crack information and are picked up by the receiver PWAS. The linear notch crack case is investigated through: (1) analytical model developed for Lamb waves interacting with a general linear damage; (2) finite element simulation. The breathing crack, which acts as a nonlinear source, is simulated using two approaches: (1) element activation/deactivation technique; (2) contact model. The theory and solving scheme of the proposed element activation/deactivation approach is discussed in detail. The signal features of different damage severities are analyzed. Crack opening, closing, stress concentration, surface collision phenomena are noticed for the breathing cracks. Mode conversion is noticed for both crack cases. The generation mechanism and mode components of the new wave packets are investigated by studying the particle motion through the plate thickness. A damage index is proposed based on the spectral amplitude ratio between the second harmonic and the excitation frequency for the breathing crack. The damage index is found capable of estimating the presence and severity of the breathing crack. The paper finishes with summary and conclusions.

Rayleigh-Lamb Waves in an Elastic Plate With Voids

1987 ◽  
Vol 54 (3) ◽  
pp. 509-512 ◽  
Author(s):  
D. S. Chandrasekharaiah
Keyword(s):  
Rayleigh Wave ◽  
Classical Theory ◽  
Elastic Plate ◽  
Lamb Waves ◽  
Plate Thickness ◽  
The Other ◽  
New Wave ◽  
Uniform Thickness ◽  
Linear Elastic ◽  
The Waves

Rayleigh-Lamb waves in a homogeneous and isotropic linear elastic plate containing a distribution of vacuous pores (voids) are studied. Assuming that the plate is of uniform thickness and that its faces are stress-free, it is found that the waves move, in general, in two uncoupled families, of which one is symmetrical with respect to the midplane of the plate and the other antisymmetrical; each of these families is affected by the presence of voids. If the plate is thin and the frequency is small, the voids influence only the symmetric waves and, because of this influence, the waves propagate slower than their classical counterparts. If the plate thickness and the frequency are large, each of the two families degenerates into two uncoupled waves; one of these is a classical Rayleigh wave and the other is a new wave not encountered in the classical theory.

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