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Now showing items 1 - 16 of 29

  • Wave propagation in a nonlinear acoustic metamaterial beam considering third harmonic generation

    Fang, Xin   Wen, Jihong   Yu, Dianlong   Huang, Guoliang   Yin, Jianfei  

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  • Dynamic Stability of Periodic Pipes Conveying Fluid

    Yu, Dianlong   Pa?doussis, Michael P.   Shen, Huijie   Wang, Lin  

    In this paper, the stability of a periodic cantilevered pipe conveying fluid is studied theoretically by means of a novel transfer matrix method. This method is first validated by comparing the results to those available in the literature for a uniform pipe, showing that it is capable of high accuracy and displaying good convergence characteristics. Then, the stability of periodic pipes is investigated, with geometric, material-properties periodicity, and a combination of the two, showing that a considerable stabilizing effect may be achieved over different ranges of the mass parameter beta (beta = m(f)/(m(f) + m(p) ), where m(f) and m(p) are the fluid and pipe masses per unit length). The effect of other different system parameters is also probed.
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  • Flexural Vibration Band Gap in a Periodic Fluid-Conveying Pipe System Based on the Timoshenko Beam Theory

    Yu, Dianlong   Wen, Jihong   Zhao, Honggang   Liu, Yaozong   Wen, Xisen  

    The flexural vibration band gap in a periodic fluid-conveying pipe system is studied based on the Timoshenko beam theory. The band structure of the flexural wave is calculated with a transfer matrix method to investigate the gap frequency range. The effects of the rotary inertia and shear deformation on the gap frequency range are considered. The frequency response of finite periodic pipe is calculated with a finite element method to validate the gap frequency ranges. [DOI:10.1115/1.4001183]
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  • Reply to “Comment on ‘Propagation of flexural wave in periodic beam on elastic foundations’ [Phys. Lett. A 376 (2012) 626]”

    Yu, Dianlong   Wen, Jihong   Shen, Huijie   Xiao, Yong   Wen, Xisen  

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  • Absorptive properties of three-dimensional phononic crystal

    Zhao, Honggang   Liu, Yaozong   Yu, Dianlong   Wang, Gang   Wen, Jihong   Wen, Xisen  

    We consider the absorptive properties of three-dimensional phononic crystal (PC) composed of steel spheres arranged in viscoelastic rubber. The mode conversions during the Mie scattering of a single steel sphere in unbounded rubber are analyzed in detail. Then the multiple scattering (MS) and absorption effects induced by the simple cubic lattice and the viscosity of the rubber are investigated by the MS method. The results show that the shear and viscoelastic properties of the rubber are crucial, and the destructive interface induced by MS below each Bloch frequency enhances the absorption. Finally, the acoustic properties of finite PC slabs variation with the filling fraction and the incident angle are discussed for a variety of cases. The results show that the PC can be used as underwater anechoic material. (c) 2007 Published by Elsevier Ltd.
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  • Characteristics of wave propagation, vibration transmission and acoustic emission in fluid-filled coaxial periodic shells

    Shen, Huijie   Tang, Zhiyin   Su, Yongsheng   Liu, Jiangwei   Yu, Dianlong   Zhang, Ruojun  

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  • Highly efficient continuous bistable nonlinear energy sink composed of a cantilever beam with partial constrained layer damping

    Fang, Xin   Wen, Jihong   Yin, Jianfei   Yu, Dianlong  

    This paper focuses on the transient nonlinear dynamics and targeted energy transfer (TET) of a Bernoulli-Euler beam coupled to a continuous bistable nonlinear energy sink (NES). This NES comprises a cantilever beam with the partial constrained layer damping (PCLD) and an end mass controlled by a nonlinear magnetostatic interaction force. The theoretical model of the nonlinear system is built based on the Lagrange equations and assumed-modes expansion method. A new parameter system damping ratio is proposed to evaluate the TET efficiencies. Impact experiments are carried out to verify the theoretical model and mechanisms. The results show that the bistable NES can achieve high and strongly robust TET efficiencies under broad-range impacts. The shear modulus of the viscoelastic layer, the length of the PCLD and the end mass have significant influences on TET efficiencies. Analyses of the TET mechanisms in the bistable NES show the following: steady transition of the stable state is an important reason for maintaining high TET efficiencies; nonlinear beatings can occur in high-frequency, fundamental and long-period subharmonic branches; and resonance captures featuring fundamental and subharmonic also help achieve rapid energy dissipation.
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  • Stability of clamped-clamped periodic functionally graded material shells conveying fluid

    Shen, Huijie   Wen, Jihong   Yu, Dianlong   Wen, Xisen  

    The characteristics of the beam-mode stability of the fluid-conveying shell systems are investigated in this paper, under the clamped-clamped condition. A finite element model algorithm is developed to conduct the investigation. A periodic structure of functionally graded material (FGM) for the shell system, termed as PFGM shell here, is designed to enhance the stability for the shell systems, and to eliminate the stress concentration problems that exist in periodic structures. Results show that (i) the dynamical behaviors, either the divergence or the coupled-mode flutter, are all improved in such a periodic shell system; (ii) the critical velocities u(cr) for the divergent form of instability is independent of the normalized fluid density ; (iii) various critical values of exist in the system, for indentifying the coupled modes of flutter (Paidoussis-type or Hamiltonian Hopf bifurcation flutter) and for determining the mode exchange; (iv) changes of some key parameters, e.g., lengths of segments and/or grading profiles' could result in appreciable improvement on the stability of the system.
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  • Wave propagation in nonlinear metamaterial multi-atomic chains based on homotopy method

    Fang, Xin   Wen, Jihong   Yin, Jianfei   Yu, Dianlong  

    This paper studies the dispersion properties and wave propagation in the tetratomic nonlinear acoustic metamaterial chain based on the homotopy analysis method (HAM). We perform a comparison between HAM and Perturbation approach, harmonic balance method (HBM) and equivalent method. Results indicate that HAM can filter the unstable multiple periodic solutions fined by HBM and be more accurate. The succinct equivalent formulas can estimate the bandgaps. There is a limit of the dispersion solution when the nonlinearity tends to infinity. Analyses demonstrate that the energy dispersion in spectrum replaces the linear energy localization because of the hyperchaos that is induced by period-doubling bifurcations. The hyper-chaotic phenomena are demonstrated with frequency spectra, bifurcation diagram and Lyapunov Exponents. This paper further proves the chaotic bands can significantly expand the bandwidth for wave suppression. Enhancing the nonlinearity will vary the behavior of nonlinear bandgaps from independent state to coupling state and then experience a transition. Approaches to manipulate bands are elucidated. The strong nonlinearity is beneficial to expand the total width about 6 times. Moreover, lightweight, low-frequency and broadband characteristics are compatible so can be achieved simultaneously for nonlinear acoustic metamaterial. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
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  • Simple meta-structure that can achieve the quasi-perfect absorption throughout a frequency range of 200芒聙聯500 Hz at 350 脗掳C

    Xu, Wenqiang   Yu, Dianlong   Wen, Jihong  

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  • Dynamic Stability of Periodic Pipes Conveying Fluid

    Yu, Dianlong   Paidoussis, Michael P.   Shen, Huijie   Wang, Lin  

    In this paper, the stability of a periodic cantilevered pipe conveying fluid is studied theoretically by means of a novel transfer matrix method. This method is first validated by comparing the results to those available in the literature for a uniform pipe, showing that it is capable of high accuracy and displaying good convergence characteristics. Then, the stability of periodic pipes is investigated, with geometric, material-properties periodicity, and a combination of the two, showing that a considerable stabilizing effect may be achieved over different ranges of the mass parameter beta (beta = m(f)/(m(f) + m(p) ), where m(f) and m(p) are the fluid and pipe masses per unit length). The effect of other different system parameters is also probed.
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  • Wave propagation in a nonlinear acoustic metamaterial beam considering third harmonic generation

    Fang, Xin   Wen, Jihong   Yu, Dianlong   Huang, Guoliang   Yin, Jianfei  

    Nonlinear acoustic metamaterials (NAMs) provide new ways to control elastic waves. In this work, flexural wave propagation in an infinite NAM beam consisting of periodic Duffing resonators is reported by considering the third harmonic generation. Different analytical methods are proposed for the homogenized medium. By combining analytical and numerical approaches, we unveiled extensive physical properties of NAMs, including the nonlinear resonance, the effective density, the nonlinear locally resonant (NLR) bandgap, passbands, and the propagation and coupling of the fundamental and third harmonics. These characteristics are highly interrelated and they feature an identical near-field bifurcation frequency, which facilitates the prediction of functionalities. Moreover, we found that the NLR bandgap characterizes a distance-amplitude-dependent behavior that leads to a self-adaptive bandwidth in the far field. Our work will promote future studies, constructions and applications of NAMs with novel properties.
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  • Propagation of flexural wave in periodic beam on elastic foundations

    Yu, Dianlong   Wen, Jihong   Shen, Huijie   Xiao, Yong   Wen, Xisen  

    The propagation properties of flexural wave in the periodic beam on elastic foundations are studied theoretically. The wavenumbers and traveling wave characteristics in the beam on elastic foundations are analyzed. Basing on the equations of motion, the complex band structures and frequency response function are calculated by the transfer matrix method. And the Bragg and locally resonant gaps properties and the effects are researched. A gap with low frequency and wide range can exist in a beam on elastic foundations. (C) 2011 Elsevier B.V. All rights reserved.
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  • Flexural wave propagation in beams with periodically attached vibration absorbers: Band-gap behavior and band formation mechanisms

    Xiao, Yong   Wen, Jihong   Yu, Dianlong   Wen, Xisen  

    This paper is concerned with flexural wave propagation and vibration transmission in beams with periodically attached vibration absorbers. Such periodic systems feature unique wave filtering characteristics that can find applications in the control of wave propagation in flexural beam structures. The study is performed by using an exact analytical approach based on a combination of the spectral element method and periodic structure theory. Both infinite and finite periodic structures are considered. An explicit expression is provided for the calculation of propagation constants and thus the complex band structures, and it is further developed to examine the effects of various system parameters on the band-gap behavior, including the position, width and wave attenuation performance of all the band gaps. The band formation mechanisms of such periodic systems are explained via both derivations and physical models, yielding explicit equations to enable the prediction of all the band edge frequencies in an exact manner without the need to calculate propagation constants. Based on these equations, explicit formulas are further derived to determine the conditions for the transition and near-coupling between local resonance and Bragg scattering, each being a unique band-gap opening mechanism. (C) 2012 Elsevier Ltd. All rights reserved.
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  • Dynamics and sound attenuation in viscoelastic polymer containing hollow glass microspheres

    Zhao, Honggang   Liu, Yaozong   Wen, Jihong   Yu, Dianlong   Wen, Xisen  

    The practical design of composite material suggests that there is a need for an improved quantitative understanding of the interaction between acoustic waves and microspheres. The multiple scattering method is used to investigate the sound attenuation of the viscoelastic polymer containing hollow glass microspheres. Then the dynamics of the hollow glass microspheres is investigated by reference to the elements of the scattering matrices. It shows that the dilatational vibration of the microsphere plays a key role in the sound attenuation within the viscoelastic polymer composite at the quasistatic region. The thinner glass shell undergoes more severe dilatational vibration and induces more attenuation in the polymer composite. (c) 2007 American Institute of Physics.
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  • Anomalous wavefront manipulation and broadband sound absorption by metasurfaces witn periodic Subwavelength modulation

    Cai, Li   Wen, Jihong   Yu, Dianlong   Lu, Zhimiao   Chen, Xing   Zhao, Xiang  

    Both periodic subwavelength structures and phase gradient metasurfaces have opened up new degrees of freedom to manipulate the acoustic waves respectively. In this study, a periodic subwavelength structure is introduced into the metasurface to modulate the acoustic surface waves deduced by the phase gradient. Anomalous sound reflection beam steering is observed, as well as significant sound absorption is achieved with deep subwavelength thickness in a broadband frequency range as damping is considered. We comprehensively analyze the joint effect of the phase gradient and subwavelength periodic constraints. A local multiple reflections mechanism is proposed to reveal the underlying physics and the acoustic performances, showing an excellent agreement. Our realization opens a new perspective for the study of acoustic metasurfaces and paves the way for the design of novel devices such as acoustic holograms and broadband acoustic absorbers with deep subwavelength thickness. (C) 2018 Author(s).
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