The Experts below are selected from a list of 105 Experts worldwide ranked by ideXlab platform

Gil Ho Yoon - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of a partially debonded piezoelectric actuator in smart composite laminates
    Smart Materials and Structures, 2015
    Co-Authors: Bin Huang, Gil Ho Yoon
    Abstract:

    A partially debonded piezoelectric actuator in smart composite laminates was modeled using an improved layerwise displacement field and Heaviside Unit Step functions. The finite element method with four node plate element and the extended Hamilton principle were used to derive the governing equation. The effects of actuator debonding on the smart composite laminate were investigated in both the frequency and time domains. The frequency and transient responses were obtained using the mode superposition method and the Newmark time integration algorithm, respectively. Two partial actuator debonding cases were studied to investigate the debonding effects on the actuation capability of the piezoelectric actuator. The effect of actuator debonding on the natural frequencies was subtler, but severe reductions of the actuation ability were observed in both the frequency and time responses, especially in the edge debonded actuator case. The results provided confirmation that the proposed modeling could be used in virtual experiments of actuator failure in smart composite laminates.

  • Study on dynamic characteristics of smart composite laminates with partially debonded piezoelectric actuator
    Proceedings of SPIE, 2015
    Co-Authors: Bin Huang, Gil Ho Yoon
    Abstract:

    The dynamic characteristics of smart composite laminates with partially debonded piezoelectric actuator are investigated in this work. The proposed work introduces an improved layerwise theory based mathematical modeling with the Heaviside Unit Step functions to allow the possible sliding of the in-plane displacements and jump of the out-of-plane displacements for the debonded area. The finite element implementation is conducted using the four-node plate element to derive the governing equation. The dynamic characteristics are investigated by the frequency domain and time domain. The influence of actuator debonding to the natural frequencies is subtler for such kind of smart composite structures. The debonding of piezoelectric actuator also decreases its actuation ability that is reflected in the magnitudes of the system response. The proposed method can well predict the responses of the smart composite laminates with actuator debonding failures and it could be applied to the further damage detection methods.

Bin Huang - One of the best experts on this subject based on the ideXlab platform.

  • Modeling of a partially debonded piezoelectric actuator in smart composite laminates
    Smart Materials and Structures, 2015
    Co-Authors: Bin Huang, Gil Ho Yoon
    Abstract:

    A partially debonded piezoelectric actuator in smart composite laminates was modeled using an improved layerwise displacement field and Heaviside Unit Step functions. The finite element method with four node plate element and the extended Hamilton principle were used to derive the governing equation. The effects of actuator debonding on the smart composite laminate were investigated in both the frequency and time domains. The frequency and transient responses were obtained using the mode superposition method and the Newmark time integration algorithm, respectively. Two partial actuator debonding cases were studied to investigate the debonding effects on the actuation capability of the piezoelectric actuator. The effect of actuator debonding on the natural frequencies was subtler, but severe reductions of the actuation ability were observed in both the frequency and time responses, especially in the edge debonded actuator case. The results provided confirmation that the proposed modeling could be used in virtual experiments of actuator failure in smart composite laminates.

  • Study on dynamic characteristics of smart composite laminates with partially debonded piezoelectric actuator
    Proceedings of SPIE, 2015
    Co-Authors: Bin Huang, Gil Ho Yoon
    Abstract:

    The dynamic characteristics of smart composite laminates with partially debonded piezoelectric actuator are investigated in this work. The proposed work introduces an improved layerwise theory based mathematical modeling with the Heaviside Unit Step functions to allow the possible sliding of the in-plane displacements and jump of the out-of-plane displacements for the debonded area. The finite element implementation is conducted using the four-node plate element to derive the governing equation. The dynamic characteristics are investigated by the frequency domain and time domain. The influence of actuator debonding to the natural frequencies is subtler for such kind of smart composite structures. The debonding of piezoelectric actuator also decreases its actuation ability that is reflected in the magnitudes of the system response. The proposed method can well predict the responses of the smart composite laminates with actuator debonding failures and it could be applied to the further damage detection methods.

William H. Prosser - One of the best experts on this subject based on the ideXlab platform.

  • Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators
    Finite Elements in Analysis and Design, 2006
    Co-Authors: Anindya Ghoshal, Seung-bok Choi, William H. Prosser
    Abstract:

    Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside Unit Step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during ''breathing'' of the delaminated layers. In quantum mechanics, the Fermi-Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi-Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi-Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi-Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.

  • Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators
    Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems III, 2004
    Co-Authors: Anindya Ghoshal, William H. Prosser, Mark J. Schulz, Goutham R. Kirikera
    Abstract:

    Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside Unit Step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during “breathing” of the delaminated layers. In quantum mechanics, the Fermi-Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi-Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi-Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi-Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. Further applications of the Fermi-Dirac distribution function in other physics based dynamic models are suggested. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.

Alexei A. Maradudin - One of the best experts on this subject based on the ideXlab platform.

  • Surface plasmon polariton propagation near an index Step
    Optics Communications, 2005
    Co-Authors: Tamara A. Leskova, Alexei A. Maradudin, W. Zierau
    Abstract:

    Abstract In this work, we study theoretically the scattering of p-polarized light of frequency ω from, and its transmission through, a system consisting of a dielectric medium (prism) characterized by a dielectric constant ϵ 0 in the region x 3  >  D ; a metal film characterized by a complex, frequency-dependent dielectric function ϵ 1 ( ω ) in the region 0  x 3 D ; a dielectric film characterized by a dielectric constant ϵ 2 in the region ζ ( x 1 )  x 3 ϵ 3  = 1) in the region x 3 ζ ( x 1 ). The light, whose plane of incidence is the x 1 x 3 -plane, is incident through the prism. For the surface profile function ζ ( x 1 ) we assume the form ζ ( x 1 ) = −d θ ( x 1 ) θ ( L  −  x 1 ), where θ ( x 1 ) is the Heaviside Unit Step function. Thus, we have a dielectric film of thickness d and dielectric constant ϵ 2 covering the part of the lower surface ( x 3  = 0) of the metal film defined by 0  x 1 L . The reduced Rayleigh equation for the amplitude of the light scattered back into the prism, R ( q | k ), is derived, as is the reduced Rayleigh equation for the amplitude of the light transmitted into the vacuum, T ( q | k ). These integral equations are solved numerically and the results are used to calculate the intensity of the scattered field in the near- and far-field regions, and the intensity of the transmitted light in the near-field region, for several values of L and of the wavelength of the incident light. The results provide information about the scattering of the surface plasmon polariton at the metal–vacuum interface, excited by the incident light, by index Steps on that interface, which can be used to determine the thickness of the dielectric film d , its extent L , and its dielectric constant ϵ 2 .

  • Fabrication of one-dimensional random surfaces that display enhanced backscattering for only one specified angle of incidence
    Surface Scattering and Diffraction for Advanced Metrology, 2001
    Co-Authors: M. Ciftan, Tamara A. Leskova, Alexei A. Maradudin
    Abstract:

    The phenomenon of enhanced backscattering in the scattering of light from a randomly rough surface is the presence of a well-defined peak in the retroreflection direction in the angular dependence of the intensity of the light scattered diffusely from the surface. A striking feature of this phenomenon is that it occurs for any angle of incidence. Suppose, however, that one would like to have a random surface that displays enhanced backscattering for only a single, specified, angle of incidence. Such a surface could be useful, for example, in situations where one wishes to position a source (and hence the detector) at a specified direction with respect to the site at which the scattering surface is situated. In this paper we show how a one-dimensional random surface can be generated that produces an enhanced backscattering peak for only a specified angle of incidence when illuminated by p-polarized light whose plane of incidence is perpendicular to the generators of the surface. This surface is defined by a power spectrum (the Fourier transform of the surface height autocorrelation function) given by g(Q) = (π)/(4(Δ)k)[θ (Q-k1+Δk)θ(k1+Δk-Q)+θ(Q-k2+Δk-Q)θ (k2+Δk-Q)+θ(-Q-k1+Δk)θ (k1+Δk+Q)+θ(-Q-k2+Δk)θ (k2+Δk+Q)], where θ(z) is the Heaviside Unit Step function, k1= kR-k0,k2=kR-k0, k(subscript R is the real part of the wavenumber of the surface plasmon polariton of frequency ω supported by the planar vacuum-metal interface, and k0 is related to the angle of incidence measured clockwise from the x3-axis by k0=(ω/c)sinθ0. An explanation is provided for why a surface defined by this power spectrum produces enhanced backscattering at only the angle of incidence given by θs=-θ0, and it is confirmed by numerical calculations of the angular dependence of the intensity of the light scattered diffusely from it.

  • Surface plasmon polariton propagation near an index Step
    Scattering and Surface Roughness III, 2000
    Co-Authors: Tamara A. Leskova, Alexei A. Maradudin, W. Zierau
    Abstract:

    In this work we study theoretically the scattering of p-polarized light of frequency (omega) from a system consisting of a dielectric medium (prism) characterized by a dielectric constant (epsilon) 0 in the region x3 $GTR D; a metal film characterized by a complex, frequency-dependent dielectric function(epsilon) 1((omega) ) in the region 0 < x3 < D; a dielectric film characterized by a dielectric constant (epsilon) 2 in the region (zetz) (x1) < x- 3) < 0; and vacuum ((epsilon) 3 equals 1) in the region x3 < (zetz) (x1). The light whose plane of incidence is the x1x3- plane, in incident through the prism. For the surface profile function (zetz) (x1) we take the form (zetz) (x1) equals -d(theta) (x1)(theta) (L-x(1), where (theta) (x1) is the Heaviside Unit Step function. Thus we have a dielectric film thickness d and dielectric constant (epsilon) 2 covering the half of the lower surface (x3 equals 0) of the metal film defined by x1$GTR0, or a dielectric film of thickness d and dielectric constant (epsilon) 2 covering the part of the lower surface (x3 equals 0) of the metal film defined by 0 < x1 < L. The reduced Rayleigh equation for the amplitude of the light scattered back into the prism, R(qk), is obtained, and solved by the Wiener-Hopf method, and the result is used to calculate the intensity of the scattered field in the far field region as a function of x1 for a fixed value of x3 for several values of the wavelength of the incident light. The results provide information about the scattering of the surface plasmon polariton at the metal-vacuum interface, excited by the incident light, by an index Step on that interface. A brief discussion of the transmission of light through this system is also given.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • Role of the surface height correlation function in the enhanced backscattering of light from random metallic surfaces
    Proceedings of SPIE, 1991
    Co-Authors: Alexei A. Maradudin, T. Michel
    Abstract:

    It is generally believed that the enhanced backscattering of light from a highly reflecting, multiply-scattering, random surface is due to the coherent interference of each multiply- reflected optical path with its time-reversed partner, and is already present in the double- scattering approximation. If enhanced backscattering is indeed a multiple-scattering effect we should see it from any random surface that can multiply scatter light. The statistical properties of the surface, such as whether the surface profile function is a Gaussianly-distributed random variable or not, whether it is stationary or not, and the form of the surface height correlation function, should therefore be of secondary importance in determining whether enhanced backscattering occurs or not. In this paper we study the role played by the form of the surface height correlation function in the existence of enhanced backscattering and in the dependence on the scattering angle of the contribution to the mean differential reflection coefficient from the incoherent component of the scattered light. We consider the scattering of p- and s- polarized beams of light incident normally onto a random, one-dimensional metallic surface, when the plane of incidence is perpendicular to the generators of the surface. Four different forms of the surface height power spectrum g(Q) are considered: (a) g(Q) equals (pi) a exp(-Qa); (b) g(Q) equals (pi) 1/2a exp(-Q2a2/4); (c) g(Q) equals 2a[1 - (Qa/(pi) )](theta) ((pi) - Qa); and (d) g(Q) equals a(theta) ((pi) - Qa), where we have presented them in the order of increasing rate of decay to zero with increasing Q. In these expressions (theta) (Q) is the Heaviside Unit Step function. For each form of g(Q) we have calculated the mean value of , the distance between consecutive peaks and valleys on the surface and the variance of this quantity, (sigma) d equals [2> - 2]1/2. The values of these quantities are correlated with the rate of decay of g(Q) with increasing Q. For a fixed values of the wavelength of the incident light we then calculate the contribution to the mean differential reflection coefficient from the incoherent component of the scattered light when the value of a in case (b) above is varied in such a way that (lambda) / increases systematically, with the rms slope held constant. Enhanced backscattering is observed in each case. The width of the enhanced backscattering peak is related to the value of (lambda) /, as is the occurrence of first order subsidiary maxima. The latter disappear when (lambda) / has increased to about 0.6. This is interpreted as due to the inability of the incident light to resolve the structure of the surface responsible for these subsidiary maxima. Similar calculations are carried out for a band-limited fractal surface, characterized by g(Q) equals ((pi) a/tan-1Qoa)(theta) (Qo - Q)/(1 + a2Q2), and similar results are obtained. No evidence of second order subsidiary maxima is seen in the differential reflection coefficient. This result is believed to be due to the magnitude of (sigma) d/ for each of the forms of g(Q) considered. We conclude that while the detailed form of the mean differential reflection coefficient depends on the form of the surface height correlation function, the existence of enhanced backscattering does not, as long as the surface remains multiply reflecting.

Anindya Ghoshal - One of the best experts on this subject based on the ideXlab platform.

  • Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators
    Finite Elements in Analysis and Design, 2006
    Co-Authors: Anindya Ghoshal, Seung-bok Choi, William H. Prosser
    Abstract:

    Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside Unit Step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during ''breathing'' of the delaminated layers. In quantum mechanics, the Fermi-Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi-Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi-Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi-Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.

  • Modeling delamination in composite structures by incorporating the Fermi-Dirac distribution function and hybrid damage indicators
    Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems III, 2004
    Co-Authors: Anindya Ghoshal, William H. Prosser, Mark J. Schulz, Goutham R. Kirikera
    Abstract:

    Conventional finite element approaches for modeling delaminations in laminated composite structures use the Heaviside Unit Step function at the interfacial nodes in the delaminated zone of the structure to model the possible jumps in the displacement field during “breathing” of the delaminated layers. In quantum mechanics, the Fermi-Dirac distribution applies to Fermion particles whose characteristics are half-integer spins. The present paper uses the Fermi-Dirac distribution function to model a smoother transition in the displacement and the strain fields of the delaminated interfaces during the opening and closing of the delaminated layers under vibratory loads. This paper successfully shows that the Fermi-Dirac distribution function can be used to more accurately model the dynamic effects of delaminations in laminated composite structures. Optimizing the parameters in the Fermi-Dirac distribution function can lead to more accurate modeling of the dynamic and transient behavior of the delaminated zones in laminated composite structures. Further applications of the Fermi-Dirac distribution function in other physics based dynamic models are suggested. This paper also effectively demonstrates how hybrid sensors comprising of out of plane displacement sensors and in plane strain sensors can effectively map a composite structure to detect and locate the delaminated zones. It also shows how simple mode shapes can be used to determine the locations of single and multiple delaminations in laminated composite structures.