Creat membership Creat membership
Sign in

Forgot password?

Confirm
  • Forgot password?
    Sign Up
  • Confirm
    Sign In
home > search

Now showing items 1 - 16 of 43

  • Effects of locally resonant modes on underwater sound absorption in viscoelastic materials

    Wen, Jihong   Zhao, Honggang   Lv, Linmei   Yuan, Bo   Wang, Gang   Wen, Xisen  

    Recently, by introducing locally resonant scatterers with spherical shape proposed in phononic crystals into design of underwater sound absorption materials, the low-frequency underwater sound absorption phenomenon induced by the localized resonances is observed. To reveal this absorption mechanism, the effect of the locally resonant mode on underwater sound absorption should be studied. In this paper, the finite element method, which is testified efficiently by comparing the calculation results with those of the layer multiple scattering method, is introduced to investigate the dynamic modes and the corresponding sound absorption of localized resonance. The relationship between the resonance modes described with the displacement contours of one unit cell and the corresponding absorption spectra is discussed in detail, which shows that the localized resonance leads to the absorption peak, and the mode conversion from longitudinal to transverse waves at the second absorption peak is more efficient than that at the first one. Finally, to show the modeling capability of FEM and investigate shape effects of locally resonant scatterers on underwater sound absorption, the absorption properties of viscoelastic materials containing locally resonant scatterers with ellipsoidal shape are discussed. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3621074]
    Download Collect
  • Wave propagation in a nonlinear acoustic metamaterial beam considering third harmonic generation

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

    Download Collect
  • Acoustic directional radiation operating at the pass band frequency in two-dimensional phononic crystals

    Wen, Jihong   Yu, Dianlong   Cai, Li   Wen, Xisen  

    Download Collect
  • Directional propagation characteristics of flexural wave in two-dimensional periodic grid-like structures

    Wen, Jihong   Yu, Dianlong   Wang, Gang   Wen, Xisen  

    Download Collect
  • On wave propagation and attenuation properties of underwater acoustic screens consisting of periodically perforated rubber layers with metal plates

    Yang, Haibin   Xiao, Yong   Zhao, Honggang   Zhong, Jie   Wen, Jihong  

    Download Collect
  • Theoretical and experimental investigation of flexural wave propagation in straight beams with periodic structures: Application to a vibration isolation structure

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

    \0
    Download Collect
  • Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

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

    The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is "clear" and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM. (C) 2013 Elsevier B.V. All rights reserved.
    Download Collect
  • 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.
    Download Collect
  • 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.
    Download Collect
  • A tunable sound-absorbing metamaterial based on coiled-up space

    Wang, Yang   Zhao, Honggang   Yang, Haibin   Zhong, Jie   Zhao, Dan   Lu, Zhongliang   Wen, Jihong  

    This paper presents a theoretical, numerical, and experimental investigation of a deep-subwavelength absorber based on the concept of coiled-up space. By adjusting a partition panel in the cavity to form an unequal-section channel, it is found that the resonance frequency of the absorber is easily tuned and near-total absorption is acquired under a fixed deep-subwavelength thickness. The absorption mechanism induced by nearly critical coupling is revealed by graphically analyzing the reflection coefficient in the complex plane. In contrast to conventional techniques, near-total absorption can be adjusted over a wider frequency range. To further enhance the absorption, we demonstrate a broad-band absorber with a relative bandwidth up to 33.3%. Published by AIP Publishing.
    Download Collect
  • A space-coiled acoustic metamaterial with tunable low-frequency sound absorption

    Wang, Yang   Zhao, Honggang   Yang, Haibin   Zhong, Jie   Wen, Jihong  

    A novel low-frequency absorber composed a perforated panel and a cavity with a coiled-up channel is presented and demonstrated. Both theoretical analysis and finite element method are utilized to reveal that the absorber possesses a low-frequency absorption with deepsubwavelength thickness. The effect of the folding number of a space-coiled channel on the absorption peak position is discussed and the result shows that a greater folding number can reduce the absorption peak frequency dramatically without sacrificing the total thickness of the absorber. In order to broaden the absorption bandwidth, an absorber combining two units with different folding number is constructed to further enhance the low-frequency absorption performance. Copyright (C) EPLA, 2018.
    Download Collect
  • 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.
    Download Collect
  • 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/).
    Download Collect
  • 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  

    Download Collect
  • Sound transmission loss of metamaterial-based thin plates with multiple subwavelength arrays of attached resonators

    Xiao, Yong   Wen, Jihong   Wen, Xisen  

    This paper is concerned with sound transmission loss of metamaterial-based thin plates consisting of multiple subwavelength arrays of spring-mass resonators attached to an unbounded homogenous thin plate. Two analytical wave approaches are developed for the calculation of diffuse field sound transmission loss of such metamaterial-based thin plates. Numerical results show that a metamaterial-based plate can result in much higher sound transmission loss than a bare plate (with the same surface mass density) at frequencies within the mass-law region and the coincidence region. It is also demonstrated that by using an extremely thin plate to form a metanaterial-based plate, the construction can be implemented as a potential sound insulation material with good performance at low frequencies. (c) 2012 Elsevier Ltd. All rights reserved.
    Download Collect
  • Optimization of locally resonant acoustic metamaterials on underwater sound absorption characteristics

    Meng, Hao   Wen, Jihong   Zhao, Honggang   Wen, Xisen  

    The study of acoustic metamaterials, also known as locally resonant sonic materials, has recently focused on the topic of underwater sound absorption. The high absorption occurs only within a narrow frequency band around the locally resonant frequency. Nevertheless, this problem can be addressed through a combination of several acoustic metamaterial layers that have different resonant frequencies. In this paper, an optimization scheme, a genetic and a general nonlinear constrained algorithm, is utilized to enhance the low-frequency underwater sound absorption of an acoustic metamaterial slab with several layers. Both the physical and structural parameters of the acoustic metamaterial slab are optimized to enlarge the absorption band. In addition, the sound absorption mechanism of the acoustic metamaterial slab is also analyzed. The result shows that each layer is found to oscillate as a nearly independent unit at its corresponding resonant frequency. The theoretical and experimental results both demonstrate that the optimized metamaterial slab can achieve a broadband (800-2500 Hz) absorption of underwater sound, which is a helpful guidance on the design of anechoic coatings. (C) 2012 Elsevier Ltd. All rights reserved.
    Download Collect
1 2 3

Contact

If you have any feedback, Please follow the official account to submit feedback.

Turn on your phone and scan

Submit Feedback