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Ulrich Gabbert - One of the best experts on this subject based on the ideXlab platform.
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non reflecting boundary condition for Lamb Wave Propagation problems in honeycomb and cfrp plates using dashpot elements
Composites Part B-engineering, 2013Co-Authors: Seyed Mohammad Hossein Hosseini, Sascha Duczek, Ulrich GabbertAbstract:The paper’s objective is to introduce a new non-reflecting boundary condition using dashpot elements. This is an useful tool to efficiently simulate Lamb Wave Propagation within composite structures, such as honeycomb and CFRP plates. Due to the steadily increasing interest in applying Lamb Waves in modern online structural health monitoring techniques, several numerical and experimental studies have been carried out recently. The proposed boundary condition poses the advantage of reducing the computational costs required to simulate the Wave Propagation in heterogenous materials. Different parameters which can influence the functionality of such an artificial boundary are discussed and several applications are presented. Finally, the results are also experimentally validated.
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Semi-analytical finite element method for modeling of Lamb Wave Propagation
CEAS Aeronautical Journal, 2013Co-Authors: Zair Asrar Bin Ahmad, J. M. Vivar-perez, Ulrich GabbertAbstract:Lamb Wave Propagation in plates is multi-modal, dispersive and highly dependent on the material properties. In homogeneous isotropic plates, Lamb modes can be grouped into symmetric and anti-symmetric modes, and they are decoupled from the shear modes. Due to the material isotropy, Lamb Wave Propagation behavior is independent from the Propagation direction. This property can be used to find analytical solutions for the field of displacements in the frequency domain. However, in composite plates having anisotropic material properties, Lamb Wave Propagation behavior depends on the Propagation direction. For this reason, the complexity of Lamb Wave Propagation modes increases, and no direct analytical solutions are available. Thus, numerical methods need to be used. In this paper, the semi-analytical finite element (SAFE) method is applied as it is suitable for both isotropic homogeneous plates and anisotropic composite laminated plates. Dispersion curves for these complex materials are calculated using SAFE. The effect of obstacles on the reflection and transmission of Lamb Waves is considered. SAFE is also used for 2D point force response analysis. By applying the 2D point response analysis for perfectly bonded strip actuators, mode tuning behavior is calculated for general composite plates. A method to consider plate edge reflections in the 2D force response analysis is also presented.
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Membrane carrier Wave function in the modeling of Lamb Wave Propagation
CEAS Aeronautical Journal, 2013Co-Authors: J. M. Vivar-perez, Zair Asrar Bin Ahmad, Ulrich GabbertAbstract:Wave Propagation in plates are multi-modal and dispersive by nature. Their behavior is highly dependent on the material properties. In homogeneous isotropic plates Lamb modes can be grouped into symmetric and anti-symmetric modes and they are decoupled from the shear modes. Due to the material isotropy, Lamb Wave’s Propagation behavior is not dependent on the Propagation direction. This property can be used to find analytical solutions for the field of displacements in the frequency domain. In this paper, series of numerical simulations on the Lamb Wave Propagation in homogeneous isotropic are presented. The concept of the membrane carrier Wave is used together with integral transforms in the space domain, and analytical expressions are found for the response of a homogeneous isotropic plate under different load regimes. We considered line forces and axisymmetric loads applied to the plate. The procedure can be applied to other types of load distributions.
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Influence of the cover plate thickness on the Lamb Wave Propagation in honeycomb sandwich panels
CEAS Aeronautical Journal, 2013Co-Authors: S. M. H. Hosseini, Ulrich Gabbert, R. LammeringAbstract:Within this paper, the guided Lamb Wave Propagation in thin honeycomb sandwich panels is studied. The Lamb Waves are excited by thin piezoelectric (PZT) patch actuators glued to the surface of the plate, and the signals are received by similar PZT sensor patches. Such actuator and sensor systems can be used for a cost-effective online health monitoring of structures. In homogeneous plates, Lamb Waves propagate with symmetrical and anti-symmetrical modes. However, the Propagation in heterogeneous media is not as clear and depends on the exciting frequency, the material properties, and the geometry of the structure. In this paper, the influence of the geometrical properties of honeycomb plates on the Lamb Wave Propagation is studied. For this purpose detailed 3-D finite element calculations are performed, which result in very time consuming computations. Consequently, also simplified models are developed to reduce the computing time without losing the quality of the results. To this end, the honeycomb core material is replaced by a homogeneous layer with orthotropic mechanical properties. The homogenized properties are calculated numerically using a homogenization technique based on the representative volume element method. The comparison of the results received with the two different approaches has shown that the simplified models are in a good agreement with the extended models for a certain range of exciting frequencies and geometrical properties only. The Wave Propagation on the top and bottom surfaces is also compared in order to show how deep the Waves can travel inside the structure.
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numerical simulation of the Lamb Wave Propagation in honeycomb sandwich panels a parametric study
Composite Structures, 2013Co-Authors: Seyed Mohammad Hossein Hosseini, Ulrich GabbertAbstract:The paper aims to describe the guided Lamb Wave Propagation in honeycomb sandwich panels. The application of Lamb Waves is a well-known method in modern online structural health monitoring techniques. To analyze the Wave Propagation in such a complicated geometry with an analytical solution is hardly possible; therefore a dimensional finite element simulation is used. A piezoelectric actuator is used to excite the Waves on the sandwich panel surface. The extended model of the honeycomb sandwich panel is consisting of two plate layers and a mid-core layer. In addition, a simplified model is used to reduce the computing costs, where the mid-core of the sandwich panel is replaced by a homogeneous layer. The results from the extended model and the simplified model are in most cases in a good agreement; however the limitations of using the simplified model are discussed. A parametric study is used to show the influence of the geometrical properties of honeycomb plates, the material properties of the skin plates and the loading frequency on the group velocity, the Wave length and the energy transmission. Each of these properties provides valuable information to design an efficient health monitoring system. Finally, an experimental test is presented.
Seyed Mohammad Hossein Hosseini - One of the best experts on this subject based on the ideXlab platform.
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non reflecting boundary condition for Lamb Wave Propagation problems in honeycomb and cfrp plates using dashpot elements
Composites Part B-engineering, 2013Co-Authors: Seyed Mohammad Hossein Hosseini, Sascha Duczek, Ulrich GabbertAbstract:The paper’s objective is to introduce a new non-reflecting boundary condition using dashpot elements. This is an useful tool to efficiently simulate Lamb Wave Propagation within composite structures, such as honeycomb and CFRP plates. Due to the steadily increasing interest in applying Lamb Waves in modern online structural health monitoring techniques, several numerical and experimental studies have been carried out recently. The proposed boundary condition poses the advantage of reducing the computational costs required to simulate the Wave Propagation in heterogenous materials. Different parameters which can influence the functionality of such an artificial boundary are discussed and several applications are presented. Finally, the results are also experimentally validated.
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numerical simulation of the Lamb Wave Propagation in honeycomb sandwich panels a parametric study
Composite Structures, 2013Co-Authors: Seyed Mohammad Hossein Hosseini, Ulrich GabbertAbstract:The paper aims to describe the guided Lamb Wave Propagation in honeycomb sandwich panels. The application of Lamb Waves is a well-known method in modern online structural health monitoring techniques. To analyze the Wave Propagation in such a complicated geometry with an analytical solution is hardly possible; therefore a dimensional finite element simulation is used. A piezoelectric actuator is used to excite the Waves on the sandwich panel surface. The extended model of the honeycomb sandwich panel is consisting of two plate layers and a mid-core layer. In addition, a simplified model is used to reduce the computing costs, where the mid-core of the sandwich panel is replaced by a homogeneous layer. The results from the extended model and the simplified model are in most cases in a good agreement; however the limitations of using the simplified model are discussed. A parametric study is used to show the influence of the geometrical properties of honeycomb plates, the material properties of the skin plates and the loading frequency on the group velocity, the Wave length and the energy transmission. Each of these properties provides valuable information to design an efficient health monitoring system. Finally, an experimental test is presented.
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numerical simulation of the guided Lamb Wave Propagation in particle reinforced composites
Composite Structures, 2012Co-Authors: Ralf Weber, Seyed Mohammad Hossein Hosseini, Ulrich GabbertAbstract:Abstract This paper deals with the investigation of the Lamb Wave Propagation in particle reinforced composites excited by piezoelectric patch actuators. A three-dimensional finite element method (FEM) modeling approach is set up to perform parameter studies in order to better understand how the Lamb Wave Propagation in particle reinforced composite plates is affected by change of central frequency of excitation signal, volume fraction of particles, size of particles and stiffness to density ratio of particles. Furthermore, the influence of different arrangements is investigated. Finally, the results of simplified models using material data obtained from numerical homogenization are compared to the results of models with heterogeneous build-up. The results show that the Lamb Wave Propagation properties are mainly affected by the volume fraction and ratio of stiffness to density of particles, whereas the particle size does not affect the Lamb Wave Propagation in the considered range. As the contribution of the stiffer material increases, the group velocity and the Wave length also increase while the energy transmission reduces. Simplified models based on homogenization technique enabled a tremendous drop in computational costs and show reasonable agreement in terms of group velocity and Wave length.
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analysis of guided Lamb Wave Propagation gw in honeycomb sandwich panels
Pamm, 2010Co-Authors: Seyed Mohammad Hossein Hosseini, Ulrich GabbertAbstract:The paper aims to introduce the guided Lamb Wave Propagation (GW) in a honeycomb sandwich panels to be used in the health monitoring applications. Honeycomb sandwich panels are well-known as lightweight structures with a good stiffness behavior and a wide range of applications in different industries. Due to the complex geometry and complicated boundary conditions in such a structure, the development of analytical solutions for describing the Wave Propagation and the interaction of Waves with damages is hardly possible. Therefore dimensional finite element simulations have been used to model GW for different frequency ranges and different sandwich panels with different geometrical properties. The Waves, which are highly dispersive, have been excited by thin piezoelectric patches attached to the surface of the structure. In the first step, the honeycomb panel has been simplified as an orthotropic layered continuum medium. The required material data have been calculated by applying a numerical homogenization method for the honeycomb core layer. The Wave Propagation has been compared in the homogenized model with the real geometry of a honeycomb sandwich panel. Such calculations of high frequency ultrasonic Waves are costly, both in creating a proper finite element model as well as in the required calculation time. In this paper the influence of changes in the geometry of the sandwich panel on the Wave Propagation is presented. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)
Mingxi Deng - One of the best experts on this subject based on the ideXlab platform.
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response of second harmonic generation of Lamb Wave Propagation to microdamage thickness in a solid plate
Wave Motion, 2020Co-Authors: Ning Hu, Mingxi Deng, Han Chen, Yanxun XiangAbstract:Abstract The response features of second-harmonic generation (SHG) of primary Lamb Wave Propagation to the thickness of microdamage layer (MDL) in a solid plate have been theoretically and numerically investigated in this paper. Here the solid plate with a MDL is regarded as a double-layered plate in analysis of nonlinear Lamb Wave Propagation. On the basis of a second-order perturbation approximation and modal expansion analysis, the physical process of cumulative SHG by primary Lamb Wave Propagation in a solid plate with a MDL has been investigated. The influence of variation in the thickness of MDL on the effect of SHG of primary S 0 mode, which satisfies an approximate phase velocity matching in the low frequency region, has been theoretically analyzed, and then the finite element (FE) simulation has been carried out to validate the results of the theoretical predictions. A close agreement between the theoretical analyses and FE simulations validates the effectiveness of using the effect of SHG of primary S 0 mode for characterizing changes in the thickness of MDL. Moreover, change mechanism of nonlinear acoustic parameter with the thickness of MDL is revealed It is expected that the results obtained can provide a convenient means for accurately characterizing nonhomogeneous microdamage (MDL thickness) in layered plates.
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time domain analysis and experimental examination of cumulative second harmonic generation by primary Lamb Wave Propagation
Journal of Applied Physics, 2011Co-Authors: Mingxi Deng, Yanxun XiangAbstract:Within the second-order perturbation approximation, the physical process of cumulative second-harmonic generation by the primary Lamb Wave Propagation has been investigated in the time domain. Based on the preconditions that the transfer of energy from the primary Lamb Wave to the double frequency Lamb Wave is not zero and that the phase velocity matching condition is satisfied, we focus on analyzing the influence of mismatching of the group velocities on the generation of the second harmonic by Propagation of a primary Lamb Wave tone burst with a finite duration. Our analysis indicates that the time-domain envelope of the second harmonic generated is dependent on the Propagation distance when both the duration of the primary Lamb Wave tone burst and the group velocity mismatch are given. Furthermore, it can be concluded that the integrated amplitude of the time-domain second harmonic, which quantifies the efficiency of the second-harmonic generation, grows with the Propagation distance even when the grou...
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Development of general solution of cumulative second harmonic by Lamb Wave Propagation
2008 IEEE Ultrasonics Symposium, 2008Co-Authors: Mingxi DengAbstract:A straightforward approach has been developed for the general solution of the cumulative second harmonic by Lamb Wave Propagation in a solid plate. The present analyses of second-harmonic generation by Lamb Waves focus on the cases where the phase velocity of the fundamental Lamb Wave is exactly or approximately equal to that of the dominant double frequency Lamb Wave (DFLW). Based on the general solution obtained, the numerical analyses show that the cumulative second-harmonic fields are associated with the position of excitation source and the difference between the phase velocity of the fundamental Lamb Wave and that of the dominant DFLW component.
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Characterization of elastic anisotropy of a solid plate using nonlinear Lamb Wave approach
Journal of Sound and Vibration, 2007Co-Authors: Mingxi Deng, Jun YangAbstract:Abstract A nonlinear Lamb Wave approach is presented for characterizing the in-plane elastic anisotropy of a solid plate. The effect of second-harmonic generation in an anisotropic solid plate exists and through this the Lamb Waves propagate. When the direction of the Lamb Wave Propagation in an anisotropic plate changes, the influences of the elastic anisotropy of the plate material on the second-harmonic generation of the Lamb Wave Propagation have been analyzed. Theoretical analyses show that the effect of second-harmonic generation of the Lamb Wave Propagation is closely associated with the elastic anisotropy of the solid plate. Based on the theoretical analyses, characterization of the in-plane elastic anisotropy of a given rolled aluminum sheet is experimentally studied. For the different directions of the Lamb Wave Propagation relative to the rolling direction of the aluminum sheet, the amplitude–frequency curves both of the fundamental Waves and the second harmonics of Lamb Wave Propagation are measured under the condition that the Lamb Waves have a strong nonlinearity. It is found that the in-plane elastic anisotropy of the rolled aluminum sheet can clearly affect the efficiency of second-harmonic generation by the Lamb Wave Propagation. The stress Wave factors (SWFs) in acousto-ultrasonic technique are used for reference. Based on the data measured, the normalized SWF curves of the Lamb Wave Propagation versus the orientation angles relative to the rolling direction of the aluminum sheet are obtained. The results show that the second-harmonic SWF of the Lamb Wave Propagation varies more sensitively with the orientation angles than does the SWF of the fundamental Lamb Wave Propagation. It is found that the effect of second-harmonic generation of the Lamb Wave Propagation can be used to accurately characterize the in-plane elastic anisotropy for the given solid plate.
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P2L-2 Study of Second-Harmonic Generation of Lamb Waves Propagating in Layered Planar Structures with Weak Interfaces
2006 IEEE Ultrasonics Symposium, 2006Co-Authors: Mingxi Deng, Ping Wang, Xiafu LvAbstract:The physical process of second-harmonic generation by the primary Lamb Waves, propagating in layered planar structures with weak interfaces, has been studied in this paper. Due to the kinematic nonlinearity and the elastic nonlinearity of materials, there is second-harmonic generation accompanying the primary Lamb Wave Propagation. The well-known finite interfacial stiffness technique is used to describe the properties of weak interfaces of layered planar structures. It is found that the finite normal and tangential interfacial stiffnesses will effectively influence the effect of second-harmonic generation by Lamb Wave Propagation at the modal expansion coefficients of the Double Frequency Lamb Waves (abbr. DFLWs, constituting the second-harmonic fields) and at the dispersion relations of Lamb Waves (determining the degree of cumulative growth of a DFLW component). Relative to the case where the interface of a layered planar structure is perfect and the phase velocity of the DFLW component is equal to that of the primary Lamb Wave Propagation at a given frequency where the DFLW component grows with Propagation distance, the efficiency of second-harmonic generation of the primary Lamb Wave Propagation will decrease greatly when the normal and tangential interfacial stiffnesses decrease. The effect of second-harmonic generation by the primary Lamb Wave Propagation may provide a potential for accurately characterizing the properties of weak interfaces of layered planar structures
Xiafu Lv - One of the best experts on this subject based on the ideXlab platform.
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P2L-2 Study of Second-Harmonic Generation of Lamb Waves Propagating in Layered Planar Structures with Weak Interfaces
2006 IEEE Ultrasonics Symposium, 2006Co-Authors: Mingxi Deng, Ping Wang, Xiafu LvAbstract:The physical process of second-harmonic generation by the primary Lamb Waves, propagating in layered planar structures with weak interfaces, has been studied in this paper. Due to the kinematic nonlinearity and the elastic nonlinearity of materials, there is second-harmonic generation accompanying the primary Lamb Wave Propagation. The well-known finite interfacial stiffness technique is used to describe the properties of weak interfaces of layered planar structures. It is found that the finite normal and tangential interfacial stiffnesses will effectively influence the effect of second-harmonic generation by Lamb Wave Propagation at the modal expansion coefficients of the Double Frequency Lamb Waves (abbr. DFLWs, constituting the second-harmonic fields) and at the dispersion relations of Lamb Waves (determining the degree of cumulative growth of a DFLW component). Relative to the case where the interface of a layered planar structure is perfect and the phase velocity of the DFLW component is equal to that of the primary Lamb Wave Propagation at a given frequency where the DFLW component grows with Propagation distance, the efficiency of second-harmonic generation of the primary Lamb Wave Propagation will decrease greatly when the normal and tangential interfacial stiffnesses decrease. The effect of second-harmonic generation by the primary Lamb Wave Propagation may provide a potential for accurately characterizing the properties of weak interfaces of layered planar structures
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experimental verification of cumulative growth effect of second harmonics of Lamb Wave Propagation in an elastic plate
Applied Physics Letters, 2005Co-Authors: Mingxi Deng, Ping Wang, Xiafu LvAbstract:Wedge transducers are used to generate and detect the primary (fundamental) Waves and second harmonics of Lamb Wave Propagation on the surface of an elastic plate. The amplitudes of the primary Waves and the second harmonics on the plate surface are measured for different separations of the transmitting and receiving wedge transducers. In the immediate vicinity of a driving frequency at which the primary and the double-frequency Lamb Waves have the same phase velocities, the quantitative relationships of the second-harmonic amplitudes on Propagation distance are analyzed. It is experimentally verified that the second harmonics of primary Lamb Waves have a cumulative growth effect with Propagation distance.
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experimental observation of cumulative second harmonic generation of Lamb Wave Propagation in an elastic plate
Journal of Physics D, 2005Co-Authors: Mingxi Deng, Ping Wang, Xiafu LvAbstract:The experimental observation of cumulative second-harmonic generation of the primary (fundamental) Lamb-Wave Propagation is reported in this paper. Using the dispersion relations for Lamb Waves and the modal expansion analysis approach for Waveguide excitation, a straightforward model has been presented for analysing the physical process of generation of the time-domain pulses of the second harmonics by the fundamental time-domain pulses of the primary Lamb-Wave Propagation. The physical meaning of the integrated amplitudes, both of the fundamental Waves and the second harmonics, is clearly illustrated. Wedge transducers are used to generate and detect the fundamental Waves and the second harmonics of the Lamb-Wave Propagation on the surface of an elastic plate. The clear second-harmonic signals can be observed near the frequency at which Lamb Waves have a strong nonlinearity. The amplitudes of the fundamental Waves and the second harmonics of the Lamb-Wave Propagation on the plate surface are measured for different separations between the transmitting and receiving wedge transducers. In the immediate vicinity of a driving frequency at which the fundamental and the double-frequency Lamb Waves have the same phase velocities, the quantitative relationships between the second-harmonic amplitudes and Propagation distance are analysed. It is observed that the second harmonics of primary Lamb Waves grow with Propagation distance.
Guangyao Li - One of the best experts on this subject based on the ideXlab platform.
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asymmetric Lamb Wave Propagation in phononic crystal slabs with graded grating
Journal of Applied Physics, 2013Co-Authors: Jiujiu Chen, Guangyao LiAbstract:Asymmetric Lamb Wave Propagation is important for control and manipulation of the Lamb Wave signals in various devices. Through numerical simulation of the Lamb Wave Propagation in phononic crystal slabs with graded grating, we proposed and studied a linear phononic device that shows asymmetric Lamb Wave transmission in low-frequency domains. This exotic phenomenon stems from the threshold frequency of the fundamental antisymmetric Lamb mode conversion to the fundamental symmetric Lamb mode is different at the different locations of the acoustic diode. Remarkably, a bi-directional asymmetric Lamb Wave Propagation is achieved by tuning the grade of the grating depths. The back propagating acoustic Waves of the second band of hybridized Lamb modes plays the essential role in the phenomena for relatively high-frequency regions. This should be potentially significant in helping design chip-scale integrated phononic devices.
