scholarly journals Ultra-Wide Bandgap in Two-Dimensional Metamaterial Embedded with Acoustic Black Hole Structures

2021 ◽  
Vol 11 (24) ◽  
pp. 11788
Author(s):  
Xiaofei Lyu ◽  
Qian Ding ◽  
Zhisai Ma ◽  
Tianzhi Yang
Keyword(s):  
Cell Wall ◽  
Black Hole ◽  
Vibration Isolation ◽  
Hexagonal Lattice ◽  
Wide Bandgap ◽  
Vibration Modes ◽  
Practical Application ◽  
Equipment Development ◽  
Lumped Masses ◽  
Local Stiffness

This paper reports a type of metamaterial plate enabling in-plane ultra-wide vibration isolation in engineering equipment development. It is composed of periodic hexagonal lattice structures. The acoustic black hole (ABH) structures are embedded in each cell wall of the conventional hexagonal lattice, which results in the reduction of local stiffness in the cell wall and the local mass in the hexagonal corner. The lattice can be simplified as the form of lumped masses vibrating on springs, and two types of eigenstates can be obtained: the rotational eigenstates and the transverse eigenstates. The geometric nonlinearity of the ABH structure leads to unevenly distributed vibration modes, resulting in the ultra-wide bandgap. Experimental results prove the effective attenuation capacity. Compared with the traditional hexagonal lattice, the proposed design provides greater advantages in practical application.

Sound absorption based on Micro-perforated panels and Acoustic Black Hole principle

2021 ◽  
Vol 263 (6) ◽  
pp. 548-555
Author(s):  
Xiaoqi Zhang ◽  
Li Cheng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Sound Absorption ◽  
Practical Application ◽  
Inner Radius ◽  
Simulation Results ◽  
Structural Configurations ◽  
Acoustic Black Holes ◽  
Sound Reduction ◽  
Bending Wave

Acoustic black holes (ABHs) have been so far investigated mainly for bending wave ma-nipulation in mechanical structures such as beams or plates. The investigations on ABHs for sound wave manipulation, referred to as Sonic black holes (SBHs) are scarce. Existing SBH structure for sound reduction in air is typically formed by putting a set of rings inside a duct wall with decreasing inner radius according to a power law. As such, the structure is very complex and difficult to be practically realized, which hampers the practical application of SBHs for sound reduction. This study explores the possibilities of achieving SBH effects using other types of structural configurations. In particular, micro-perforated panels are proposed to be introduced into the conventional SBH structure, and the simulation results show that the new formed SBH structure is simpler in configuration in terms of number of rings and more efficient in terms of sound energy trapping and dissipation.

Origami-Based Bistable Metastructures for Low-Frequency Vibration Control

2021 ◽  
Vol 88 (5) ◽  
Author(s):  
Mingkai Zhang ◽  
Jinkyu Yang ◽  
Rui Zhu
Keyword(s):  
Vibration Isolation ◽  
Energy Analysis ◽  
Geometrical Nonlinearity ◽  
Low Frequency ◽  
Quantitative Relationship ◽  
Vibration Modes ◽  
Two Dimensional ◽  
Low Frequency Vibration ◽  
Dynamic Experiments ◽  
Unit Cells

Abstract In this research, we aim to combine origami units with vibration-filtering metastructures. By employing the bistable origami structure as resonant unit cells, we propose metastructures with low-frequency vibration isolation ability. The geometrical nonlinearity of the origami building block is harnessed for the adjustable stiffness of the metastructure’s resonant unit. The quantitative relationship between the overall stiffness and geometric parameter of the origami unit is revealed through the potential energy analysis. Both static and dynamic experiments are conducted on the bistable origami cell and the constructed beam-like metastructure to verify the adjustable stiffness and the tunable vibration isolation zone, respectively. Finally, a two-dimensional (2D) plate-like metastructure is designed and numerically studied for the control of different vibration modes. The proposed origami-based metastructures can be potentially useful in various engineering applications where structures with vibration isolation abilities are appreciated.

Optimizing Vibration Isolation of Flex Circuits in Hard Disk Drives

2003 ◽  
Author(s):  
M. Brake ◽  
J. A. Wickert
Keyword(s):  
Vibration Isolation ◽  
Longitudinal Vibration ◽  
Hard Disk Drives ◽  
Experimental Studies ◽  
Hard Disk ◽  
Disk Drive ◽  
Vibration Modes ◽  
Disk Drives ◽  
Electronic Components ◽  
Write Heads

Flex circuits are a laminate of polyimide substrate, adhesive, and copper conductors, and they are used to connect the (stationary) electronic components in a hard disk drive to the (rotating) arm that positions the read/write heads above the disk. The transverse and longitudinal vibration of flex circuits couples with motion of the read/write heads and contributes to increased settling time and residual vibration following repositioning of the arm from one data track to another. In this paper, the results of parameter, optimization, and experimental studies are discussed with a view toward increasing the isolation of vibration between the flex circuit to the arm in terms of a metric involving one or several important vibration modes.

Influence of Loading on Mode Localization in Periodic Structures

1995 ◽  
Vol 48 (11S) ◽  
pp. S132-S137 ◽  
Author(s):  
Reyolando M. L. R. F. Brasil ◽  
Carlos E. N. Mazzilli
Keyword(s):  
Small Parameter ◽  
Periodic Structures ◽  
Computer Code ◽  
Vibration Modes ◽  
Finite Element Program ◽  
Mode Localization ◽  
Element Program ◽  
The Masses ◽  
Lumped Masses ◽  
Two Degree Of Freedom

This paper addresses the problem of the presence of a slightly disordered loading in otherwise ordered periodic structures as an element to trigger the phenomenon of vibration mode localization due to its effect in their stiffness. The sample structures are basically cantilever columns supporting the loads due to large lumped masses in their top which may vary according to a disorder related small parameter. They are connected by very flexible springs. A first series of results deals with a two-degree-of-freedom model where localization is achieved due to loading disorder. The frequencies and displacements show very sharp and nonlinear variation when the small parameter changes slightly around its zero value. The results for this simple model compare well with those of a finite element program developed by the authors. For a more complex example, another model of a rank of six columns is analyzed by the same computer code. A pseudo-random variation of the masses is considered and the resulting vibration modes are compared to those of the ordered structure, which are global in nature and present a sinusoidal spatial distribution. Again, due to mode localization, motions in the perturbed structure are found to be restricted largely to one of the masses.

Comparison of Cell Wall Microstructure of Aluminum Foams Produced by Melt Foaming and Gas Injection Foaming Processes

2013 ◽  
Vol 457-458 ◽  
pp. 540-543
Author(s):  
Yu Tong Zhou ◽  
Yan Xiang Li ◽  
Xing Nan Liu ◽  
Wen Wen Yuan
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Base Alloy ◽  
Gas Injection ◽  
Secondary Phases ◽  
Practical Application ◽  
Aluminum Foams ◽  
Foaming Process ◽  
Metallurgical Structure ◽  
The Difference

Aluminum foams from A356 base alloy were produced by both the melt foaming process and gas injection foaming process. A comparison of microstructures between the two kinds of aluminum foams was carried out. The related causes were analyzed to form the difference in microstructure. Results indicate that aluminum foams produced by different processes are distinct in metallurgical structure. The average thickness of cell wall, the species and area fraction of secondary phases or particles and other metallurgical features have been all comparatively studied. The difference in microstructure features of the cell walls will also make the aluminum foams different in mechanical properties. Therefore, we need to select proper foaming process for aluminum foams according to the property requirements in practical application.

scholarly journals A Report on Fungal (1→3)-α-d-glucans: Properties, Functions and Application

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3972 ◽  
Author(s):  
Katarzyna Złotko ◽  
Adrian Wiater ◽  
Adam Waśko ◽  
Małgorzata Pleszczyńska ◽  
Roman Paduch ◽  
...  
Keyword(s):  
Cell Wall ◽  
Immune System ◽  
Physicochemical Properties ◽  
Aspergillus Fumigatus ◽  
Cell Walls ◽  
Practical Application ◽  
Fungal Cell ◽  
Plant Infection ◽  
Potential Use

The cell walls of fungi are composed of glycoproteins, chitin, and α- and β-glucans. Although there are many reports on β-glucans, α-glucan polysaccharides are not yet fully understood. This review characterizes the physicochemical properties and functions of (1→3)-α-d-glucans. Particular attention has been paid to practical application and the effect of glucans in various respects, taking into account unfavourable effects and potential use. The role of α-glucans in plant infection has been proven, and collected facts have confirmed the characteristics of Aspergillus fumigatus infection associated with the presence of glucan in fungal cell wall. Like β-glucans, there are now evidence that α-glucans can also stimulate the immune system. Moreover, α-d-glucans have the ability to induce mutanases and can thus decompose plaque.

Thermal Stresses in Rectangular Plates

1959 ◽  
Vol 10 (1) ◽  
pp. 65-78 ◽  
Author(s):  
J. S. Przemieniecki
Keyword(s):  
Thermal Stresses ◽  
Plate Thickness ◽  
Normal Modes ◽  
Thermoelastic Stress ◽  
Characteristic Functions ◽  
Vibration Modes ◽  
Rectangular Plates ◽  
Practical Application ◽  
Flat Plates ◽  
Modes Of Vibration

SummaryThe characteristic functions for beam vibration modes are used to derive an approximate solution for the calculation of thermal stresses in rectangular isotropic flat plates subjected to arbitrary temperature distributions in the plane of the plate and constant temperatures through the plate thickness. The thermal stresses are obtained in the form of generalised Fourier expansions in terms of the characteristic functions, and their derivatives, representing normal modes of vibration of a clamped-clamped beam. Since these functions have recently been tabulated, the practical application of this new method to the thermoelastic stress analysis of plates presents no difficulty.

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