Man, X, Luo, Z, Liu, J & Xia, B 2019, 'Hilbert fractal acoustic metamaterials with negative mass density and bulk modulus on subwavelength scale', Materials and Design, vol. 180.View/Download from: UTS OPUS or Publisher's site
© 2019 The Authors Acoustic metamaterials (AMs) are artificially engineered composite materials, structured to have unconventional effective properties for flexibly manipulating the wave propagation, which can produce a broad range of applications such as sound cloaking and tunneling. In nature, bio-inspired fractal organization with multiple length scales has been found in various biological materials, which display enhanced dynamic properties. By introducing Hilbert curve channels, this work will design a class of topological architectures of Hilbert fractal acoustic metamaterials (HFAMs) with negative mass density and bulk modulus on subwavelength scale. In this paper, we will highlight the influences of the self-similar fractal configurations on multipole modes of HFAM. To further demonstrate multipole resonances, the pressure magnifications are assessed in the center region of HFAM with losses. Moreover, based on effective medium theory, we systematically calculate and investigate effective bulk modulus and mass density, as well as density-near-zero of HFAM, to demonstrate the negative properties and the zero-phase-difference effects of HFAMs. Numerical results show that HFAM can enable a number of applications, from sound blocking, quarter bending, sound cloaking to sound tunneling, and may further provide a possibility for the engineering guidances of the exotic properties on subwavelength scale.
Man, X-F, Xia, B-Z, Luo, Z & Liu, J 2019, '3D Hilbert fractal acoustic metamaterials: low-frequency and multi-band sound insulation', Journal of Physics D: Applied Physics, vol. 52, no. 19.View/Download from: UTS OPUS or Publisher's site
Man, X, Liu, T, Xia, B, Luo, Z & Longxiang, X 2018, 'Space-coiling fractal metamaterial with multi-bandgaps on subwavelength scale', Journal of Sound and Vibration, vol. 423, pp. 322-339.View/Download from: UTS OPUS or Publisher's site
Acoustic metamaterials are remarkably different from conventional materials, as they can flexibly manipulate and control the propagation of sound waves. Unlike the locally resonant metamaterials introduced in earlier studies, we designed an ultraslow artificial structure with a sound speed much lower than that in air. In this paper, the space-coiling approach is proposed for achieving artificial metamaterial for extremely low-frequency airborne sound. In addition, the self-similar fractal technique is utilized for designing space-coiling Mie-resonance-based metamaterials (MRMMs) to obtain a band-dispersive spectrum. The band structures of two-dimensional (2D) acoustic metamaterials with different fractal levels are illustrated using the finite element method. The low-frequency bandgap can easily be formed, and multi-bandgap properties are observed in high-level fractals. Furthermore, the designed MRMMs with higher order fractal space coiling shows a good robustness against irregular arrangement. Besides, the proposed artificial structure was found to modify and control the radiation field arbitrarily. Thus, this work provides useful guidelines for the design of acoustic filtering devices and acoustic wavefront shaping applications on the subwavelength scale.
Liu, J, Chen, J, Xia, B & Man, X 2018, 'Bandgap optimization of photonic crystal based on interval model', Zhendong yu Chongji/Journal of Vibration and Shock, vol. 37, no. 17, pp. 115-121.View/Download from: Publisher's site
© 2018, Editorial Office of Journal of Vibration and Shock. All right reserved. The traditional optimization design of photonic crystal is based on a deterministic acoustic model. However, uncertainties widely exist in photonic crystal and seriously affect its acoustic properties. Here, an interval model was introduced to describe uncertainties of its system parameters. Then, Chebyshev polynomial was employed to construct the surrogate model of energy band structure of photonic crystal to analyze influences of uncertain parameters on photonic crystal's bandgap. Finally, taking photonic crystal bandgap's maximization as the objective function, taking bandgap variation range as the constrained condition, the interval photonic crystal reliability optimization model based on Chebyshev surrogate model was constructed. The genetic algorithm was used to solve this optimization model. Numerical results showed that Chebyshev surrogate model can effectively and accurately predict the bandgap variation range of photonic crystal based on the interval model; when interval uncertainties are considered, the optimization model of photonic crystal based on Chebyshev surrogate model can maximize the bandgap variation range to significantly improve the sound shielding performance of photonic crystal.
Liu, J, Li, L, Xia, B & Man, X 2018, 'Fractal labyrinthine acoustic metamaterial in planar lattices', International Journal of Solids and Structures, vol. 132-133, pp. 20-30.View/Download from: Publisher's site
© 2017 Elsevier Ltd Labyrinthine acoustic metamaterial provides a flexible and unprecedented ability to manipulate the sound wave propagation, such as sound blocking, cloaking, supertunneling etc. However, the design of labyrinthine acoustic metamaterial with excellent properties remains challenging with a traditional zigzag channel. Here, we develop a class of fractal-inspired labyrinthine acoustic metamaterials with hierarchical zigzag channels and highlight the influences of the self-similar fractal hierarchies on their band structures. Band structures of fractal-inspired labyrinthine acoustic metamaterials in the five representative Bravais lattices are also investigated. Our results show that the self-similar fractal can be effectively used to widen the total band gaps and lower the frequency of the first bandgap. Furthermore, for the second order fractal labyrinthine acoustic metamaterial arranged in different Bravais lattices, several excellently wide bandgaps appear in the different frequency ranges. By actively-tuning the Bravais lattice, we have a chance to yield excellently wide and tunable bandgaps. Thus, this work provides an insight into the critical role of the self-similar fractal on the band structure of the labyrinthine acoustic metamaterial, and gives a guidance for the selection of Bravais lattices with a desired band structure.
Liu, J, Man, X, Guo, Y & Chen, N 2017, 'A hybrid uncertain analysis approach for structural-acoustic problems with random and evidence variables', Noise Control Engineering Journal, vol. 65, no. 3, pp. 158-173.View/Download from: Publisher's site
© 2017 Institute of Noise Control Engineering. In this paper, a hybrid uncertain analysis approach is introduced for the structural-acoustic problem with random variables and evidence variables existed simultaneously. In this uncertain structural-acoustic model, the uncertain parameters with sufficient information are treated as random variables, while some uncertain parameters with limited information are assumed as evidence variables. Based on the deterministic formulation of the structural-acoustic system, the response of the hybrid uncertain structural-acoustic problem is specifically deduced. In order to alleviate the computational cost, the intervals of the expectation and variance of the response are computed by combining the evidence theory method, the random interval moment method and the vertex method. A numerical example is presented to show the feasibility and effectiveness of the proposed approach.
Xie, L, Liu, J, Zhang, J & Man, X 2017, 'Evidence-Theory-Based Analysis for Structural-Acoustic Field with Epistemic Uncertainties', International Journal of Computational Methods, vol. 14, no. 2.View/Download from: Publisher's site
© 2017 World Scientific Publishing Company. Evidence theory has a strong capacity to deal with epistemic uncertainty, in view of the overestimation in interval analysis, the responses of structural-acoustic problem with epistemic uncertainty could be untreated. In this paper, a numerical method is proposed for structural-acoustic system response analysis under epistemic uncertainties based on evidence theory. To improve the calculation accuracy and reduce the computational cost, the interval analysis technique and radial point interpolation method are adopted to obtain the approximate frequency response characteristics for each focal element, and the corresponding formulations of structural-acoustic system for interval response analysis are deduced. Numerical examples are introduced to illustrate the efficiency of the proposed method.