scholarly journals Wave Propagation in Periodic Metallic Structures with Equilateral Triangular Holes

2020 ◽  
Vol 10 (5) ◽  
pp. 1600 ◽  
Author(s):  
Antonio Alex-Amor ◽  
Guido Valerio ◽  
Fatemeh Ghasemifard ◽  
Francisco Mesa ◽  
Pablo Padilla ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Physical Mechanism ◽  
Geometrical Parameters ◽  
Metallic Structures ◽  
Symmetric Configuration ◽  
Parallel Plate Waveguide ◽  
Depth Separation ◽  
Physical Insight ◽  
Elliptical Holes ◽  
High Degree

This paper studies wave propagation in a periodic parallel-plate waveguide with equilateral triangular holes. A mode-matching method is implemented to analyze the dispersion diagram of the structure possessing glide and mirror symmetries. Both structures present an unexpected high degree of isotropy, despite the triangle not being symmetric with respect to rotations of 90°. We give some physical insight on the matter by carrying out a modal decomposition of the total field on the hole and identifying the most significant modes. Additionally, we demonstrate that the electrical size of the triangular hole plays a fundamental role in the physical mechanism that causes that isotropic behavior. Finally, we characterize the influence of the different geometrical parameters that conform the unit cell (period, triangle size, hole depth, separation between metallic plates). The glide-symmetric configuration offers higher equivalent refractive indexes and widens the stopband compared to the mirror-symmetric configuration. We show that the stopband is wider as the triangle size is bigger, unlike holey structures composed of circular and elliptical holes where an optimal hole size exists.

Development of Flexible Worktable for Endmilling Based on Parallel Mechanism

2010 ◽  
Vol 447-448 ◽  
pp. 826-830 ◽  
Author(s):  
Tomohisa Tanaka ◽  
Masahiro Komori ◽  
Jiang Zhu ◽  
Yoshio Saito
Keyword(s):  
Machine Tools ◽  
Parallel Mechanism ◽  
High Accuracy ◽  
The Other ◽  
Geometrical Parameters ◽  
Basic Design ◽  
Positioning Accuracy ◽  
Accuracy Measurement ◽  
High Degree ◽  
Work Table

Parallel mechanism has many advantages, such as high stiffness, high accuracy, high degree of freedom (DOF), etc. These fine features are suitable for work table of machine tools for production of recent complicated designs. In this study, six axes linear-actuated parallel mechanism was chosen as the basic design for work table. First, geometrical parameters of the table were designed to satisfy the required movable range with minimum cutting load. Then, the work table was actually constructed and its performance was evaluated. From positioning accuracy measurement, it was found that the table is suitable to be used for machining of complicated products. On the other hand, from actual cutting tests of primitive shapes using chemical wood and measurement of the machined shapes, potential of the table for real cutting application was confirmed.

Wave Propagation in Periodic Stiffened Shells: Spectral Finite Element Modeling and Experiments

2003 ◽  
Vol 9 (9) ◽  
pp. 1057-1081 ◽  
Author(s):  
G. Solaroli ◽  
Z. Gu ◽  
A. Baz ◽  
M. Ruzzene
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Periodic Structures ◽  
Dynamic Stiffness ◽  
Geometrical Parameters ◽  
Pass Band ◽  
Matrix Formulation ◽  
Stiffened Shell ◽  
Stiffened Shells ◽  
Spectral Finite Element

The capability of periodic structures to act as filters for propagating waves is used to control the propagation of waves in thin shells. The shells are stiffened by periodically placed rings in order to generate periodic discontinuities in the stiffness and inertial spatial distribution along the longitudinal axes of these shells. Such discontinuities result in attenuation of the wave propagation over certain frequency bands called stop bands. A distributed-parameter approach is used to derive a spectral finite element model of the periodically stiffened shell. The model accurately describes the dynamic behavior of the shell using a small number of elements. The stiffening rings, modeled using the curved beam theory, are considered as lumped elements whose mass and stiffness matrices are combined with those of the shell. The resulting dynamic stiffness matrix of the ring-stiffened shell element is used to predict the wave propagation dynamics in the structure. In particular, the shell propagation constants are determined by solving a polynomial eigenvalue problem, as a numerically robust alternative to the traditional transfer matrix formulation. The study of the propagation constants shows that the discontinuity introduced by the stiffeners generates the typical stop/pass band pattern of periodic structures. The location and width of the stop bands depend on the spacing and geometrical parameters of the rings. The existence of the stop bands, as predicted from the analysis of the propagation constants, is verified experimentally. Excellent agreement between theoretical predictions and experimental results is achieved. The presented theoretical and experimental techniques provide viable means for designing periodically stiffened shells with desired attenuation and filtering characteristics.

scholarly journals Considerations on the Use of Explosive Substances for the Destruction of Metallic Structures

2019 ◽  
Vol 24 (2) ◽  
pp. 139-144
Author(s):  
Florin Ilie ◽  
Mircea Vladu ◽  
Gabriela Mihăilă-Lică ◽  
Bogdan-Mihai Georgescu
Keyword(s):  
Public Order ◽  
Metallic Materials ◽  
Metallic Elements ◽  
Metallic Structure ◽  
Destructive Effect ◽  
Metallic Structures ◽  
Degree Of Risk ◽  
Explosive Substance ◽  
High Degree

Abstract Incidents with IEDs containing metallic elements in the vicinity of the explosive substance pose a high degree of risk, endangering safety, peace and public order. In such situations, the methods and procedures applied as response by the authorities are cumbersome and risky, given the improvised nature of these incidents. In this paper we intend to analyze the destructive effect of explosive substances on certain metallic materials and we focus on a U-shaped metallic structure.

FOCUSING LIGHT WITH TYPICAL SUBWAVELENGTH PATTERNED METALLIC STRUCTURES

2012 ◽  
Vol 26 (22) ◽  
pp. 1250144 ◽  
Author(s):  
ZHEN GUO ◽  
LIANSHAN YAN ◽  
KUNHUA WEN ◽  
XIANGANG LUO
Keyword(s):  
Boundary Condition ◽  
Numerical Simulations ◽  
Geometrical Parameters ◽  
Metallic Structures ◽  
Theoretical Results ◽  
Focusing Properties

Two typical subwavelength nano-lenses, nano-slits and nano-grooves, are investigated based on the diffraction and electromagnetic boundary condition. Detailed and systematic analyses for the focusing properties of the two structures with different geometrical parameters are carried out. Theoretical results agree well with those in the numerical simulations and experiments. Compared to the nano-grooves, nano-slits with appropriate geometrical parameters show higher efficiency and better focusing performance.

scholarly journals Control of Dynamics in Weak PMA Magnets

2021 ◽  
Vol 7 (3) ◽  
pp. 43
Author(s):  
Luis M. Álvarez-Prado
Keyword(s):  
Thin Film ◽  
Wave Propagation ◽  
Magnetic Fields ◽  
Spin Wave ◽  
Ferromagnetic Resonance ◽  
Applied Field ◽  
Magnetic Thin Film ◽  
Micromagnetic Simulations ◽  
Domain Structures ◽  
High Degree

We have recently shown that a hybrid magnetic thin film with orthogonal anisotropies presenting weak stripe domains can achieve a high degree of controllability of its ferromagnetic resonance. This work explores the origin of the reconfigurability through micromagnetic simulations. The static domain structures which control the thin film resonance can be found under a deterministic applied field protocol. In contrast to similar systems reported, our effect can be obtained under low magnetic fields. We have also found through simulations that the spin wave propagation in the hybrid is nonreciprocal: two adjacent regions emit antiparallel spin waves along the stripe domains. Both properties convert the hybrid in a candidate for future magnonic devices at the nanoscale.

scholarly journals Glide-Symmetric Metallic Structures With Elliptical Holes for Lens Compression

2020 ◽  
Vol 68 (10) ◽  
pp. 4236-4248 ◽  
Author(s):  
Antonio Alex-Amor ◽  
Fatemeh Ghasemifard ◽  
Guido Valerio ◽  
Mahsa Ebrahimpouri ◽  
Pablo Padilla ◽  
...  
Keyword(s):  
Metallic Structures ◽  
Elliptical Holes
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