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Trees as large-scale natural phononic crystals: Simulation and experimental verification

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International Soil and Water Conservation Research 2019年第2期7卷 196-202页

作者： Jiankun Huang Yifan Liu Yaguang Li Key Laboratory of State Forestry Administration on Soil and Water Conservation School of Soil and Water ConservationBeijing Forestry UniversityBeijingChina

Urban trees are usually planted on a periodic layout in the spatial configuration.We regard urban trees as large-scale natural phononic crystals.The entire forest is reduced to a reasonable 'tree-soil' unit cell based on the phononic crystal theory and finite element method by COMSOL software is used to obtain the dispersion curves.The Rayleigh wave band gaps of phononic trees are distinguished by the sound cone method.The influences of soil elastic modulus and tree height on band gaps are investigated.A three-dimensional simulation model and experiment test are applied to validate the effect of phononic trees on vibration control.The numerical frequency reduction zones coincide exactly with the theoretical band gaps.Increasing soil stiffness results in a higher-frequency and wider band gap.An increasing tree height is beneficial to obtain low-frequency band gaps.A periodically arranged plantation that Rayleigh wave band gaps at frequency ≤60 Hz could be designed.This study opens up a new theoretical basis for the quantitative analyses of urban trees to the ground vibration mitigation at a certain frequency range.

关键词： Urban trees phononic crystal Dispersion curve Band gap Rayleigh wave

Merging phononic crystals and acoustic black holes

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 279-288页

作者： Xiaofei LYU Qian DING Tianzhi YANG Department of Mechanics Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Nonlinear Dynamics and Control Tianjin 300350China

phononic crystals(PCs) have recently been developed as effective components for vibration suppression and sound absorption. As a typical design of PCs, wave attenuation occurs in the so-called stop-band. However, the structural response is still significantly large in the pass-band. In this paper, we combine PCs and acoustic black holes(ABHs) in a unique device, achieving a versatile device that can attenuate vibration in the stop-band, while suppress vibration in the pass-band. This approach provides a versatile platform for controlling vibration in a multiband with a simple design.

关键词： acoustic black hole(ABH) phononic crystal(PC) transfer matrix method(TMM)

Three-Phase Microstructure Topology Optimization of Two-Dimensional phononic Bandgap Materials Using Genetic Algorithms

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Acta Mechanica Solida Sinica 2018年第6期31卷 775-784页

作者： WeiKai Xu Jinying Ning Meng Zhang Wei Wang Tianzhi Yang Key Laboratory of Liaoning Province for Composite Structural Analysis of Aerocraft and Simulation Shenyang Aerospace UniversityShenyang 110136China School of Civil Engineering Shenyang Jianzhu UniversityShenyang 110168China Department of Mechanics Tianjin UniversityTianjin 300072China

The bandgap,an important characteristic of the periodic structure,is dispersionrelated,which can be designed by tailoring the layout of materials within the periodic microstructures.A typical example of a periodic structure is phononic crystals (PnCs),which are traditionally fabricated from two-phase materials.Herein,we investigate the topologies of periodic three-phase PnCs.The microstructures of the three-phase PnCs are optimized using a two-stage genetic algorithm,and three case studies are proposed to obtain the following:(1)the maximum relative bandgap width,(2)the maximum absolute bandgap width,and (3)the max- imum bandgap at a specified frequency.More importantly,the three-phase material provides significant advantages compared to the typical two-phase materials,such as a low-frequency bandgap.This research is expected to contribute highly to vibration and noise isolation,elastic wave filters,and acoustic devices.

关键词： phononic bandgap materials Multiphase microstructures Topology optimization

Study on the vibration band gap and vibration attenuation property of phononic crystals

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Science China(Technological Sciences) 2008年第1期51卷 85-99页

作者： WEN JiHong WANG Gang YU DianLong ZHAO HongGang LIU YaoZong WEN XiSen College of Mechantronic Engineering and Automation National University of Defense TechnologyChangsha 410073China

phononic crystals (PCs) are functional materials with periodic structures and elas- tic wave (vibration) band gaps, where propagation of vibrations with frequencies within band gaps is forbidden. PCs with finite periods can restrain the propagation of vibrations with frequencies in band gaps and thus has vibration attenuation property. Worldwide, many institutions and researchers are engaged in the re- search of PCs, however, studies on the vibration attenuation property of PCs are still limited. In this paper, we report our study of band gaps and vibration attenua- tion properties of 1) a simplified PC—periodic mass-spring structures, 2) longitu- dinal vibration of one-dimensional (1D-), 2D-, 3D-PCs, and 3) the flexural vibration of 1D- and 2D-PCs. These studies provide a foundation for the applications of PCs in vibration attenuation.

关键词： phononic crystals elastic band gaps vibration band gaps vibration attenuation

Wavelet-based method for computing elastic band gaps of one-dimensional phononic crystals

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Science China(Physics,Mechanics & Astronomy) 2007年第5期50卷 622-630页

作者： YAN ZhiZhong WANG YueSheng Institute of Engineering Mechanics Beijing Jiaotong University Beijing 100044 China Institute of Engineering Mechanics Beijing Jiaotong University Beijing 100044 China

A wavelet-based method was developed to compute elastic band gaps of one-dimensional phononic crystals. The wave field was expanded in the wavelet basis and an equivalent eigenvalue problem was derived in a matrix form involving the adaptive computation of integrals of the wavelets. The method was then applied to a binary system. For comparison, the elastic band gaps of the same one-dimensional phononic crystals computed with the wavelet method and the well- known plane wave expansion (PWE) method are both presented in this paper. The numerical results of the two methods are in good agreement while the computation costs of the wavelet method are much lower than that of PWE method. In addition, the adaptability of wavelets makes the method possible for efficient band gap computation of more complex phononic structures.

关键词： phononic crystals, elastic band gap, wavelet method, plane wave expansion (PWE) method

Band Gaps and Single Scattering of phononic Crystal

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Advances in Materials Physics and Chemistry 2011年第3期1卷 86-90页

作者： Xiaoyi Huang Jingcui Peng Huanyou Wang Gui Jin 不详

A method is introduced to study the transmission and scattering properties of acoustic waves in two–dimen- sional phononic band gap (PBG) materials. First, it is used to calculate the transmission coefficients of PBG samples. Second, the transmitted power is calculated based on the far field approach. We have also calcu- lated the scattering cross section, the results indicate that phononic band gap appear in frequency regions between two well separated resonance states.

关键词： phononic Crystal Band Gap Single Scattering

Wave propagation in beams with anti-symmetric piezoelectric shunting arrays

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Chinese Physics B 2016年第3期25卷 231-236页

作者：陈圣兵王刚 China Aerodynamics Research and Development Center Mianyang 621000 China College of Mechanical and Vehicle Engineering Hunan University Changsha 410082 China

Piezoelectric shunting arrays are employed to control the wave propagation in flexible beams. Contrary to conven- tional symmetric configuration, a substrate beam with anti-symmetric shunting arrays is investigated by adapted transfer matrix method. Compared with symmetric scheme, the anti-symmetric one demonstrates some distinctive characteristics. Primarily, the longitudinal and fiexural waves are coupled, so they are correlated and must be considered simultaneously. Moreover, the attenuation of flexural wave is much stronger in anti-symmetric scenario, while the longitudinal wave demon- strates the converse side. As a result, the anti-symmetric scheme can be utilized to improve the vibration isolation capability of shunting arrays. Finally, the theoretical analyses are validated by finite element simulations.

关键词： piezoelectric shunting metamaterial phononic band gaps

Flexural Wave Bandgap Property of a Periodic Pipe with Axial Load and Hydro-Pressure

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Acta Mechanica Solida Sinica 2019年第2期32卷 173-185页

作者： Jiangwei Liu Dianlong Yu Zhenfang Zhang Huijie Shen Jihong Wen Vibration and Acoustics Research Group Laboratory of Science and Technology on Integrated Logistics Support College of Mechatronics Engineering and Automation National University of Defense Technology Changsha 410073 China College of Power Engineering Naval University of Engineering Wuhan 430033 China

A periodical composite material pipe is proposed based on the Bragg scattering mechanism of phononic crystals (PCs). The band gap (BG) properties of the flexural wave in this PC pipe under axial load and hydro-pressure are calculated using the transfer matrix (TM) method. The frequency response functions (FRFs) of the PC pipe under axial load and hydro-pressure are calculated using the finite element approach, and the mechanism is elucidated to illustrate the phenomenon. The results show that axial load and hydro-pressure and their combination all have a great influence on the flexural vibration proper ties. This research offers theoretical support for research on PC pipes with complex conditions and is of great significance in solving the problem of high pressure.

关键词： phononic crystals Flexural vibration properties Axial load Hydro-pressure

Tunable band gaps in acoustic metamaterials with periodic arrays of resonant shunted piezos

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Chinese Physics B 2013年第7期22卷 262-266页

作者：陈圣兵温激鸿王刚温熙森 Laboratory of Science and Technology on Integrated Logistics Support National University of Defense Technology Key Laboratory of Photonic and phononic Crystal of Ministry of Education National University of Defense Technology

Periodic arrays of resonant shunted piezoelectric patches are employed to control the wave propagation in a two-dimensional （2D） acoustic metamaterial. The performance is characterized by the finite element method. More importantly, we propose an approach to solving the conventional issue of the nonlinear eigenvalue problem, and give a convenient solution to the dispersion properties of 2D metamaterials with periodic arrays of resonant shunts in this article. Based on this modeling method, the dispersion relations of a 2D metamaterial with periodic arrays of resonant shunted piezos are calculated. The results show that the internal resonances of the shunting system split the dispersion curves, thereby forming a locally resonant band gap. However, unlike the conventional locally resonant gap, the vibrations in this locally resonant gap are unable to be completely localized in oscillators consisting of shunting inductors and piezo-patches.

关键词： piezoelectric shunting metamaterial phononic band gaps