Scattering of Lamb Waves by a Cylindrical Mass Attached to the Surface of a Plate

2016 ◽  
Author(s):  
Andrew Golato ◽  
Sridhar Santhanam ◽  
Fauzia Ahmad ◽  
Moeness G. Amin
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Plate Theory ◽  
Wave Mode ◽  
Guided Wave ◽  
Potential Functions ◽  
Mindlin Plate ◽  
Detection Scheme ◽  
Linear System Of Equations ◽  
Scattering Response

Defect classification is the logical next step after localization in a Lamb wave based Guided Wave Structural Health Monitoring (GWSHM) defect detection scheme. Lamb waves are a preferred wave mode in GWSHM; therefore, classification can be facilitated via understanding of the Lamb wave scattering characteristics of defects. Many defects can be modeled either as (part-) through holes or accumulated masses on the surface. We consider and analytically solve the scenario of an attached mass on the surface of a plate. The mass is treated as an elastic isotropic homogeneous cylinder and the scattering response is obtained for incident fundamental symmetric and antisymmetric waves. Propagation is modeled via Mindlin plate theory, utilizing infinite series of Bessel functions as potential functions. Boundary and continuity conditions provide a linear system of equations for the expansion coefficients of the potential functions, which, solved numerically, produce the scattering response of the defect.

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.

Inspection of Concrete-Metal Rod Interface Using Guided Waves

2000 ◽  
Author(s):  
Won-Bae Na ◽  
Tribikram Kundu ◽  
Mohammad R. Ehsani
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Guided Wave ◽  
Ultrasonic Transducers ◽  
Interface Debonding ◽  
Long Distance ◽  
Steel Rebar ◽  
Steel Bars ◽  
Steel Rebars

Abstract The feasibility of detecting interface degradation and separation of steel rebars in concrete beams using Lamb waves is investigated in this paper. It is shown that Lamb waves can easily detect these defects. A special coupler between the steel rebar and ultrasonic transducers has been used to launch non-axisymmetric guided waves in the steel rebar. This investigation shows that the Lamb wave inspection technique is an efficient and effective tool for health monitoring of reinforced concrete structures because the Lamb wave can propagate a long distance along the reinforcing steel bars embedded in concrete as the guided wave and is sensitive to the interface debonding between the steel rebar and concrete.

scholarly journals Leaky Lamb Wave Radiation from a Waveguide Plate with Finite Width

2020 ◽  
Vol 10 (22) ◽  
pp. 8104
Author(s):  
Sang-Jin Park ◽  
Hoe-Woong Kim ◽  
Young-Sang Joo
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Wave Radiation ◽  
Finite Width ◽  
Propagation Characteristics ◽  
Radiation Characteristics ◽  
Radiation Beam ◽  
Leaky Lamb Wave ◽  
Waveguide Sensor

In this paper, leaky Lamb wave radiation from a waveguide plate with finite width is investigated to gain a basic understanding of the radiation characteristics of the plate-type waveguide sensor. Although the leaky Lamb wave behavior has already been theoretically revealed, most studies have only dealt with two dimensional radiations of a single leaky Lamb wave mode in an infinitely wide plate, and the effect of the width modes (that are additionally formed by the lateral sides of the plate) on leaky Lamb wave radiation has not been fully addressed. This work aimed to explain the propagation behavior and characteristics of the Lamb waves induced by the existence of the width modes and to reveal their effects on leaky Lamb wave radiation for the performance improvement of the waveguide sensor. To investigate the effect of the width modes in a waveguide plate with finite width, propagation characteristics of the Lamb waves were analyzed by the semi-analytical finite element (SAFE) method. Then, the Lamb wave radiation was computationally modeled on the basis of the analyzed propagation characteristics and was also experimentally measured for comparison. From the modeled and measured results of the leaky radiation beam, it was found that the width modes could affect leaky Lamb wave radiation with the mode superposition and radiation characteristics were significantly changed depending on the wave phase of the superposed modes on the radiation surface.

Modeling Ultrasonic Elastic Waves in Fiber-Metal Laminate Structures in Presence of Sources and Defects

2020 ◽  
Vol 3 (4) ◽  
Author(s):  
Steffen Tai ◽  
Fumika Kotobuki ◽  
Lifu Wang ◽  
Ajit Mal
Keyword(s):  
Lamb Wave ◽  
Scattering Problem ◽  
Excitation Frequency ◽  
Guided Wave ◽  
System Response ◽  
Multilayered Structures ◽  
Detection Scheme ◽  
Element Discretization ◽  
Local Method ◽  
Fiber Metal

Abstract This paper presents a modeling and simulation method for studying ultrasonic guided wave propagation in hybrid metal-composites, also known as fiber-metal laminates. The objective is to develop an efficient and versatile modeling tool to aid in the design of cost-effective nondestructive evaluation technologies. The global–local method, which combines finite element discretization and Lamb wave modal expansion is used. An extension to the traditional global–local method is made to couple the source problem with the scattering problem to deal with a surface source generating Lamb waves that interact with defects in multilayered structures. This framework is used to study the sensitivity of different excitation frequencies to ply gap defects of various sizes. The coupled model considers the transducer contact conditions and the ultrasonic system response in the Lamb wave excitation, along with the scattering phenomenon caused by the defects. This combined result is used to define the optimal excitation frequency for the strongest transmission or reflection for a given defect size that can be observed in a physical experiment. Such results can be applied to the design of a damage detection scheme in realistic aerospace structures.

Metal-Core Piezoelectric Fibers for the Detection of Lamb Waves

2010 ◽  
Author(s):  
Jian Liu ◽  
Jinhao Qiu ◽  
Weijie Chang ◽  
Hongli Ji ◽  
Kongjun Zhu
Keyword(s):  
Lamb Wave ◽  
Piezoelectric Effect ◽  
Lamb Waves ◽  
Guided Wave ◽  
Voltage Response ◽  
Metal Core ◽  
Direct Piezoelectric Effect ◽  
New Type ◽  
Sensor Voltage ◽  
Piezoelectric Fiber

Metal-core piezoelectric fiber (MPF) is a new type of piezoelectric ceramic device with small size, and has great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. This paper focuses on the use of MPF as ultrasonic Lamb wave receivers. First, the MPF sensor voltage response is derived by coupling the direct piezoelectric effect to the wave strain field excited by circular crested actuator. The obtained theoretical result is validated on an aluminum plate. Furthermore, the experiment that compares the MPF response to Lamb wave with the PZT response is performed. The results show that MPF sensors can be used to sense Lamb waves clearly. In the end, the directivity of MPF response to Lamb waves was investigated, and another experiment is performed to examine the directivity of MPF response to Lamb waves. The result shows that MPF has high directivity, which can be exploited to triangulate the location of an ultrasound source without prior knowledge of the wave velocity in the medium.

Suppressing Technique of the Antisymmetric Mode by the Superposition of Lamb Waves Generated by Two Laser Beams in a Thin Plate

2006 ◽  
Vol 321-323 ◽  
pp. 103-107
Author(s):  
Seung Seok Lee ◽  
Sang Whoe Dho
Keyword(s):  
Thin Plate ◽  
Opposite Direction ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Laser Beams ◽  
Symmetric Mode ◽  
Antisymmetric Mode

We present a suppressing technique of the antisymmetric mode by superposition of Lamb waves generated by two laser beams in a thin plate. Two Lamb waves of the same frequency propagating from the opposite direction simultaneously arrive at the point of measurement and are superposed to compose one Lamb wave. The amplitude of the superposed Lamb wave depends on the distance between two laser beams. The suppressing of antisymmetric Lamb wave mode is accomplished by selecting the distance between two beams which simultaneously satisfies the condition of the anti-node(maximum) for the symmetric mode and the minimum for the antisymmetric mode. By this method, the antisymmetric Lamb wave mode is suppressed to the degree of 1.4% of the amplitude measured at zero distance between two beams.

scholarly journals Defect Imaging Enhancement through Optimized Shape Factors of the RAPID Algorithm Based on Guided Wave Beam Pattern Analysis

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4029
Author(s):  
Yonghee Lee ◽  
Younho Cho
Keyword(s):  
Lamb Wave ◽  
Power Plants ◽  
Steel Plate ◽  
Shape Function ◽  
Wave Mode ◽  
Guided Wave ◽  
Beam Pattern ◽  
Waveform Analysis ◽  
Distribution Factor ◽  
Shape Factors

In this study, a modified imaging algorithm was implemented to improve the imaging accuracy for defects located on a structure. Based on analysis of the Lamb wave mode, a guided ultrasonic wave inspection technique was applied, which was able to illustrate images of defects in a 6 mm steel plate simulating containment liner plate (CLP) in nuclear power plants. The dominant Lamb wave mode was determined through short-time Fourier transform waveform analysis and imaging verification. Following tomography verification, limitations of the antisymmetric mode in the thick steel plate were identified. In addition, a modified shape factor, based on the energy distribution factor according to the beam pattern and beam width, was suggested for field applications and improved imaging accuracy. Results of the analysis revealed a beam skewing phenomenon for the Lamb wave mode. In the case of S0 2.7 MHz·mm, skewing as well as distortion effects are not observed in the experiment, while the S0 modes at 2.64 and 2.74 MHz·mm show either of them. Considering skewing width, the size of the shape function was modified. Application of the modified shape function allows us to obtain more accurate image to actual defect shape.

scholarly journals On Accuracy of Analytical Modeling of Lamb Wave Scattering at Delaminations in Multilayered Isotropic Plates

2015 ◽  
Vol 15 (08) ◽  
pp. 1540010 ◽  
Author(s):  
C. T. Ng
Keyword(s):  
Analytical Solutions ◽  
Lamb Wave ◽  
Wave Scattering ◽  
Plate Theory ◽  
Analytical Models ◽  
Mindlin Plate ◽  
Bending Rigidity ◽  
Scattering Problems ◽  
Explicit Finite Element ◽  
Isotropic Plates

The study investigates the accuracy of analytical solutions to the fundamental anti-symmetric Lamb wave scattering at delamination in multilayered isotropic plates. The analytical models are based on the wave function expansion method and Born approximation within the framework of Mindlin plate theory. The study validates the accuracy of modeling the delamination as an inhomogeneity with reduced bending rigidity in predicting Lamb wave scattering induced by geometry change at the delaminated region. A good agreement is observed between the analytical solutions and results of experimentally verified 3D explicit finite element (FE) simulations. The findings support the inhomogeneity assumption in Lamb wave scattering problems and show the feasibility of employing it in delamination characterization.

THE NONLINEARITY OF GUIDED WAVE IN AN ELASTIC PLATE

2008 ◽  
Vol 22 (11) ◽  
pp. 1135-1140 ◽  
Author(s):  
TAE-HUN LEE ◽  
IK-HWANG CHOI ◽  
KYUNG-YOUNG JHANG
Keyword(s):  
Lamb Wave ◽  
Lamb Waves ◽  
Guided Wave ◽  
Nonlinear Phenomena ◽  
Bulk Wave ◽  
Power Flux ◽  
Basic Study ◽  
Out Of Plane ◽  
Plane Displacement ◽  
Velocity Matching

The ultrasonic nonlinearity has been considered as a promising method to evaluate the material degradation, since it is sensitive to the minute variation of material properties. However, most researches were restricted to the nonlinear phenomena of bulk (longitudinal) wave propagation in the bulky medium. In the case of plate, however, the propagating elastic wave is Lamb wave of which characteristics are completely different with the bulk wave, and thus the separate study for the nonlinearity of Lamb wave is required. This paper reports the result of our basic study on the nonlinear phenomena of Lamb waves, which proposes conditions for practical application as well as for the cumulative propagation of quadratic harmonic frequency mode; (1) phase matching, (2) non-zero power flux, (3) group velocity matching, and (4) non-zero out-of-plane displacement.

scholarly journals Investigation of the relationship between the Lamb waves phase velocity and the technical condition of housing and utilities pipelines

2020 ◽  
Vol 216 ◽  
pp. 01080
Author(s):  
A.A. Ibadov ◽  
A.E. Kondrat'ev ◽  
D.A. Makueva ◽  
D.V. Sergeeva
Keyword(s):  
Phase Velocity ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Wave Mode ◽  
Technical Condition ◽  
Propagation Parameters ◽  
The Relationship

The article describes a method for determining the dependence of the Lamb waves phase velocity on the technical condition of housing and utilities pipelines, using the example of thin two-layer segments. Variations in the thickness of the considered pipeline affect the propagation parameters of the Lamb wave mode.

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