scholarly journals Correlated disorder in rainbow metamaterials for vibration attenuation

2021 ◽  
pp. 095440622098659
Author(s):  
AT Fabro ◽  
H Meng ◽  
D Chronopoulos
Keyword(s):  
Cross Section ◽  
Random Fields ◽  
Dynamic Properties ◽  
Correlation Lengths ◽  
Practical Applications ◽  
Vibration Attenuation ◽  
Transfer Matrix Approach ◽  
Unit Cells ◽  
Random Disorder ◽  
Shaped Cross Section

Metastructures are typically composed of periodic unit cells designed to present enhanced dynamic properties in which either single or multiple resonators are periodically distributed. Even though the periodic metamaterials can obtain bandgaps with outstanding vibration attenuation, the widths of bandgaps can still be narrow for some practical applications. Rainbow metamaterials have been proposed based on gradient or random profiles to provide further improved attenuation. Nonetheless, the effects of correlated random disorder on their attenuation performance remains an open challenge. This work presents an investigation on the effects of correlated disorder on the vibration attenuation of rainbow metamaterials. An analytical model using the transfer matrix approach is used to calculate the receptance functions in a finite length metastructure composed of evenly spaced non-symmetric resonators attached to a beam with Π-shaped cross-section, thus a multi-frequency metastructure. The correlated disorder is modelled using random fields and an analytical expression of the Karhunen-Loève expansion is used such that spatial correlation on the resonator properties is modified by various correlation lengths, i.e., the level of spatial smoothness. Individual samples of random fields are used to investigate the effects of the correlated disorder in the vibration attenuation of a multi-frequency metastructure. It is shown that the bandgap can be further widened when compared to uncorrelated disorder. The obtained results indicates that a combination of the gradient profile with some level of disorder, typically resulting from random fields with larger correlation lengths, tends to give improved vibration attenuation when compared to a optimized gradient rainbow metamaterial. It opens new and innovative ways for the design of broadband rainbow metastructures for vibration attenuation.

scholarly journals 3D rainbow phononic crystals for extended vibration attenuation bands

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
H. Meng ◽  
N. Bailey ◽  
Y. Chen ◽  
L. Wang ◽  
F. Ciampa ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Research Effort ◽  
Phononic Crystal ◽  
Three Dimensional ◽  
Equal Mass ◽  
Curved Beams ◽  
Vibration Attenuation ◽  
Unit Cells ◽  
Recent Developments ◽  
Manufacturing Techniques

Abstract We hereby report for the first time on the design, manufacturing and testing of a three-dimensional (3D) nearly-periodic, locally resonant phononic crystal (PnC). Most of the research effort on PnCs and metamaterials has been focused on the enhanced dynamic properties arising from their periodic design. Lately, additive manufacturing techniques have made a number of designs with intrinsically complex geometries feasible to produce. These recent developments have led to innovative solutions for broadband vibration attenuation, with a multitude of potential engineering applications. The recently introduced concept of rainbow metamaterials and PnCs has shown a significant potential for further expanding the spectrum of vibration attenuation in such structures by introducing a gradient profile for the considered unit cells. Given the above, it is expected that designing non-periodic PnCs will attract significant attention from scientists and engineers in the years to come. The proposed nearly-periodic design is based on cuboid blocks connected by curved beams, with internal voids in the blocks being implemented to adjust the local masses and generate a 3D rainbow PnC. Results show that the proposed approach can produce lightweight PnCs of a simple, manufacturable design exhibiting attenuation bandwidths more than two times larger than the equivalent periodic designs of equal mass.

scholarly journals Influence of technical parameters on the structure of annular axis braided preforms

2021 ◽  
Vol 28 (1) ◽  
pp. 160-168
Author(s):  
Xi Wang ◽  
Guoli Zhang ◽  
Xiaoping Shi ◽  
Ce Zhang
Keyword(s):  
Cross Section ◽  
Rotation Speed ◽  
Technical Parameters ◽  
Braiding Angle ◽  
Shaped Cross Section

Abstract A modified vertical braiding machine and closed annular axis mandrels with a special-shaped cross section were used to braid annular axis preforms under four different technical parameters. After measuring the braiding angles and yarn spacing of the braided preform in different areas of the mandrels, it was found that the braiding angle increased by 20.9% and the yarn spacing decreased by 19.8% when the speed of the yarn carrier was doubled. The braiding angle decreased by 31.1% and the yarn spacing increased by 28.6% when the rotation speed of the mandrels was doubled. The results show that the rotation speed of the mandrel has a slightly greater influence on the braiding angle and the yarn spacing. By using the modified braiding machine to braid the annular axis preforms, multi-layer continuous braided preforms can be achieved on compact equipment. And the structure of the annular axis braided preforms can be changed by changing the technical parameters.

scholarly journals Design of an Edge Slotted Waveguide Antenna Array Based on T-Shaped Cross-Section Waveguide

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Teng Li ◽  
Wenbin Dou
Keyword(s):  
Surface Wave ◽  
Antenna Array ◽  
Cross Section ◽  
Mutual Coupling ◽  
Dominant Mode ◽  
Waveguide Structure ◽  
Center Frequency ◽  
Sidelobe Level ◽  
Slotted Waveguide ◽  
Shaped Cross Section

An edge slotted waveguide antenna array based on T-shaped cross-section radiating waveguide is proposed. The T-shaped waveguide is analyzed and designed to operate in dominant mode around the center frequency, which has a lower profile compared with the rectangular one. The radiating slots are etched and rotated alternatively on the broadened top plate without cutting into the adjacent walls. The metal fences are inserted between slots to reduce the mutual coupling and surface wave. Therefore, the sidelobe level in E-plane is well suppressed. A 2 × 8 antenna array working at Ka-band is designed and fabricated. The measured results agree well with simulations which demonstrate this novel waveguide structure.

An analytical model of a curved beam with a T shaped cross section

2018 ◽  
Vol 416 ◽  
pp. 29-54 ◽  
Author(s):  
Andrew J. Hull ◽  
Daniel Perez ◽  
Donald L. Cox
Keyword(s):  
Analytical Model ◽  
Cross Section ◽  
Curved Beam ◽  
Shaped Cross Section

scholarly journals Feasibility Study on the Wave-Control Method using Navigation Channel with V-Shaped Cross Section

2007 ◽  
Vol 54 ◽  
pp. 771-775
Author(s):  
Osamu KUNITA ◽  
Masatoshi YUHI ◽  
Junichi YAMAZAKI ◽  
Shinya KOTAKI ◽  
Hajime ISHIDA
Keyword(s):  
Cross Section ◽  
Feasibility Study ◽  
Control Method ◽  
Navigation Channel ◽  
Shaped Cross Section ◽  
Wave Control

Stress-Strain State Exploration of Stringer Made of Composite Materials Depending on Layers Stacking Structure

2018 ◽  
Vol 284 ◽  
pp. 71-76
Author(s):  
P.V. Solovyev ◽  
A.I. Gomzin ◽  
L.A. Ishbulatov ◽  
S.N. Galyshev ◽  
F.F. Musin
Keyword(s):  
Composite Materials ◽  
Cross Section ◽  
Strain State ◽  
Stress Strain ◽  
Stress Strain State ◽  
Airplane Wing ◽  
External Loads ◽  
Stacking Structure ◽  
Composite Carbon ◽  
Shaped Cross Section

In this article the results of stress-strain state investigation for composite airplane wing stringer with different layers stacking structures are presented. As an object of research, a stringer made of composite carbon with V-shaped cross-section is considered. Due to the stress-strain state analysis of various stringer structures, the most effective structure for stringer layers stacking is selected, both in the view of providing the most rigidity and optimal perception by the stringer the field of external loads, which are most typical for the conditions of its operation.

Flexoelectric effect induced in an anisotropic bar with cubic symmetry under torsion

2019 ◽  
Vol 25 (3) ◽  
pp. 820-837
Author(s):  
AR El Dhaba ◽  
ME Gabr
Keyword(s):  
Cross Section ◽  
Gradient Elasticity ◽  
Strain Gradient Elasticity ◽  
Cubic Symmetry ◽  
Rectangular Shape ◽  
Practical Applications ◽  
Flexoelectric Effect ◽  
The Cross ◽  
Gradient Elasticity Theory ◽  
Physical Quantities

In this article, we study the flexoelectricity induced in a prismatic anisotropic bar due to torsion. The simplified strain gradient elasticity theory is considered in this study. The bar is uniform, that is, any cross-section of the bar has a rectangular shape with cubic internal structure symmetry. The traction and higher traction forces effect on the deflection and spontaneous polarization of the bar with different boundary conditions are also discussed. The induced wedge forces are also considered during this study. The magnesium oxide (MgO) physical quantities values are chosen to present a numerical example as one of the practical applications of the problem. The results are discussed and introduced graphically. The most interesting finding in this study is the wedge force directions. When the displacements inside the cross-section of the bar are uniformly distributed, the resultant wedge forces have the same inclination with the cross-section boundary. Meanwhile, if the displacement is not uniformly distributed, the wedge force inclinations with the cross-section boundary are not equal.

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