The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform

Yong Xiao - One of the best experts on this subject based on the ideXlab platform.

  • flexural wave band gaps in locally resonant thin Plates with periodically attached spring mass resonators
    Journal of Physics D, 2012
    Co-Authors: Yong Xiao
    Abstract:

    The authors study the propagation of flexural waves in a locally resonant (LR) thin Plate made of a two-dimensional periodic array of spring–mass resonators attached on a thin Homogeneous Plate. The well-known plane wave expansion method is extended to deal with such a Plate system with a periodic array of lumped resonant elements. Explicit matrix formulations are developed for the calculation of complex band structures, in which the imaginary parts of Bloch wave vectors are displayed to quantify the wave attenuation performance of band gaps. It is found that resonance-type and Bragg-type band gaps coexist in the LR Plate, and the bandwidth of these gaps can be dramatically affected by the resonant frequency of local resonators. In particular, a super-wide pseudo-directional gap can be formed by a combination of the resonance gap and Bragg gap; inside such a pseudo-gap, only a very narrow pass band exists. An explicit formula is further developed to facilitate the design of such a pseudo-gap. Finally, vibration transmission in finite LR Plates is calculated using the finite element method. Vibration transmission gaps are observed, and the results are in good agreement with the band gap properties predicted by the complex band structures.

S K Datta - One of the best experts on this subject based on the ideXlab platform.

  • on transient ultrasonic waves in a Homogeneous Plate with thin superconducting coating layers
    International Journal of Solids and Structures, 2002
    Co-Authors: Jonas A Niklasson, S K Datta
    Abstract:

    Transient guided waves excited by a line force applied on one surface of a Plate with thin superconducting anisotropic layers deposited symmetrically on both surfaces of a core metallic material are considered here. The line of force is assumed to make an arbitrary angle to an axis of symmetry of the anisotropic layer. Thus, the displacement at any point in the Plate has all the three components but it is independent of the coordinate parallel to the line force (taken as x2-axis). Attention is focused here on the coupling of the longitudinal and flexural motion with the horizontally polarized shear motion. It is shown that this coupling causes an interchange between longitudinal (or flexural) and shear horizontal modes at certain frequencies, which are not high. As a result, when the center frequency of a narrow band excitation is near one of the strong coupling frequencies the received signal has characteristic features that are quite different than for other frequencies. These features could be used to characterize in-plane anisotropy of the thin layers using transducers operating at moderate frequencies. 2002 Elsevier Science Ltd. All rights reserved.

Yen Ling Chung - One of the best experts on this subject based on the ideXlab platform.

  • MECHANICAL BEHAVIOR OF FUNCTIONALLY GRADED MATERIAL PlateS UNDER TRANSVERSE LOAD-PART I: ANALYSIS
    International Journal of Solids and Structures, 2006
    Co-Authors: Yen Ling Chung
    Abstract:

    Abstract An elastic, rectangular, and simply supported, functionally graded material (FGM) Plate of medium thickness subjected to transverse loading has been investigated. The Poisson’s ratios of the FGM Plates are assumed to be constant, but their Young’s moduli vary continuously throughout the thickness direction according to the volume fraction of constituents defined by power-law, sigmoid, or exponential function. Based on the classical Plate theory and Fourier series expansion, the series solutions of power-law FGM (simply called P-FGM), sigmoid FGM (S-FGM), and exponential FGM (E-FGM) Plates are obtained. The analytical solutions of P-, S- and E-FGM Plates are proved by the numerical results of finite element method. The closed-form solutions illustrated by Fourier series expression are given in Part I of this paper. The closed-form and finite element solutions are compared and discussed in Part II of this paper. Results reveal that the formulations of the solutions of FGM Plates and Homogeneous Plates are similar, except the bending stiffness of Plates. The bending stiffness of a Homogeneous Plate is Eh 3 /12(1 −  ν 2 ), while the expressions of the bending stiffness of FGM Plates are more complicated combination of material properties.

  • Mechanical behavior of functionally graded material Plates under transverse load-Part I: Analysis
    International Journal of Solids and Structures, 2006
    Co-Authors: Shyang H. Chi, Yen Ling Chung
    Abstract:

    An elastic, rectangular, and simply supported, functionally graded material (FGM) Plate of medium thickness subjected to transverse loading has been investigated. The Poisson's ratios of the FGM Plates are assumed to be constant, but their Young's moduli vary continuously throughout the thickness direction according to the volume fraction of constituents defined by power-law, sigmoid, or exponential function. Based on the classical Plate theory and Fourier series expansion, the series solutions of power-law FGM (simply called P-FGM), sigmoid FGM (S-FGM), and exponential FGM (E-FGM) Plates are obtained. The analytical solutions of P-, S- and E-FGM Plates are proved by the numerical results of finite element method. The closed-form solutions illustrated by Fourier series expression are given in Part I of this paper. The closed-form and finite element solutions are compared and discussed in Part II of this paper. Results reveal that the formulations of the solutions of FGM Plates and Homogeneous Plates are similar, except the bending stiffness of Plates. The bending stiffness of a Homogeneous Plate is Eh3/12(1 - ν2), while the expressions of the bending stiffness of FGM Plates are more complicated combination of material properties. © 2005 Elsevier Ltd. All rights reserved.

Jonas A Niklasson - One of the best experts on this subject based on the ideXlab platform.

  • on transient ultrasonic waves in a Homogeneous Plate with thin superconducting coating layers
    International Journal of Solids and Structures, 2002
    Co-Authors: Jonas A Niklasson, S K Datta
    Abstract:

    Transient guided waves excited by a line force applied on one surface of a Plate with thin superconducting anisotropic layers deposited symmetrically on both surfaces of a core metallic material are considered here. The line of force is assumed to make an arbitrary angle to an axis of symmetry of the anisotropic layer. Thus, the displacement at any point in the Plate has all the three components but it is independent of the coordinate parallel to the line force (taken as x2-axis). Attention is focused here on the coupling of the longitudinal and flexural motion with the horizontally polarized shear motion. It is shown that this coupling causes an interchange between longitudinal (or flexural) and shear horizontal modes at certain frequencies, which are not high. As a result, when the center frequency of a narrow band excitation is near one of the strong coupling frequencies the received signal has characteristic features that are quite different than for other frequencies. These features could be used to characterize in-plane anisotropy of the thin layers using transducers operating at moderate frequencies. 2002 Elsevier Science Ltd. All rights reserved.

Yan Pennec - One of the best experts on this subject based on the ideXlab platform.

  • band structure and wave guiding in a phononic crystal constituted by a periodic array of dots deposited on a Homogeneous Plate
    SPIE Photonic West Photonic and Phononic Crystal Materials and Devices IX, 2009
    Co-Authors: B Djafarirouhani, Yan Pennec, H Larabi
    Abstract:

    Using the finite difference time domain method, we investigate theoretically the band structure and phonon transport in a phononic crystal constituted by a periodical array of cylindrical dots deposited on a thin Plate of a Homogeneous material. We show that this structure can display a low frequency gap, as compared to the acoustic wavelengths in the constituent materials, similarly to the case of locally resonant structures. The opening of this gap is discussed as a function of the geometrical parameters of the structure, in particular the thickness of the Homogeneous Plate and the height of the dots. We show the persistence of this gap for various combinations of the materials constituting the Plate and the dots. Besides, the band structure can exhibit one or more higher gaps whose number increases with the height of the cylinders. The results are discussed for different shapes of the cylinders such as circular, square or rotated square. The band structure can also display an isolated branch with a negative slope which can be useful for the purpose of negative refraction phenomena. We discuss the condition to realize wave guiding through different types of linear defects inside such a phononic crystal. Finally, we investigate the phonon transport between two substrates connected by a periodic array of dots. We discuss different features appearing in the transmission spectra such as the Perot-Fabry type oscillations related to the height and the nature of the dots, the existence of transmission gaps related to the period and the nature of the substrate, the possibility of a narrow transmission peak close to a zero of transmission.

  • low frequency gaps in a phononic crystal constituted of cylindrical dots deposited on a thin Homogeneous Plate
    Physical Review B, 2008
    Co-Authors: Yan Pennec, B Djafarirouhani, H Larabi, Jero Me Vasseur, A C Hladkyhennion
    Abstract:

    We investigate theoretically the band structure of a phononic crystal of finite thickness constituted of a periodical array of cylindrical dots deposited on a thin Plate of a Homogeneous material. We show that this structure can display a low-frequency gap, as compared to the acoustic wavelengths in the constituent materials, similarly to the case of locally resonant structures. The opening of this gap requires an appropriate choice of the geometrical parameters, and in particular the thickness of the Homogeneous Plate and the height of the dots. However, the gap persists for various combinations of the materials constituting the Plate and the dots. Besides, the band structure can exhibit one or more higher gaps whose number increases with the height of the cylinders. We discuss the condition to realize waveguiding through a linear defect inside the phononic crystal dots. The numerical simulations are performed by using the finite difference time domain and the finite element methods.

  • band gaps in a phononic crystal constituted by cylindrical dots on a Homogeneous Plate
    Journal of the Acoustical Society of America, 2008
    Co-Authors: B Djafarirouhani, Yan Pennec, H Larabi, Jero Me Vasseur, Annechristine Hladky
    Abstract:

    Using the finite difference time domain (FDTD) and the finite element (FE) methods, we investigate theoretically the band structure of a phononic crystal constituted by a periodic array of cylindrical dots deposited on a thin Homogeneous Plate. We demonstrate that such a structure can exhibit a very low frequency absolute band gap as compared to the wavelength in the constituent materials. The occurrence of this gap requires an appropriate choice of the geometrical parameters and, in particular, of the thickness of the Plate as compared to the period or to the height of the cylinders. However, the same behavior can be obtained for various combinations of the materials constituting the Homogeneous Plate and the dots. We study in detail the width of this band gap as a function of the geometrical and physical parameters of the structure. On the other hand, the structure can also exhibit one or more higher gaps whose numbers can be increased by increasing the height of the cylinders.