Numerical study of the propagation of Rayleigh and Lamb waves in orthotropic periodic structures

1987 ◽  
Vol 23 (11) ◽  
pp. 1013-1017 ◽  
Author(s):  
A. N. Podlipenets ◽  
N. A. Shul'ga
Keyword(s):  
Lamb Waves ◽  
Periodic Structures ◽  
Numerical Study

scholarly journals A Parameter Study of Localization

1996 ◽  
Vol 3 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Sandor Stephen Mester ◽  
Haym Benaroya
Keyword(s):  
Periodic Structures ◽  
Numerical Study ◽  
Vibration Characteristics ◽  
Periodic Pattern ◽  
Parameter Study ◽  
Structural Damping ◽  
One Dimensional

Extensive work has been done on the vibration characteristics of perfectly periodic structures. Disorder in the periodic pattern has been found to lead to localization in one-dimensional periodic structures. It is important to understand localization because it causes energy to be concentrated near the disorder and may cause an overestimation of structural damping. A numerical study is conducted to obtain a better understanding of localization. It is found that any mode, even the first, can localize due to the presence of small imperfections.

scholarly journals Особенности релаксации тензора напряжения в микроскопическом объеме нематической фазы под действием сильного электрического поля

2018 ◽  
Vol 60 (2) ◽  
pp. 405
Author(s):  
А.В. Захаров
Keyword(s):  
Dissipation Rate ◽  
Periodic Structures ◽  
Numerical Study ◽  
Strong Electric Field ◽  
Rectangular Channel ◽  
Energy Dissipation Rate ◽  
Director Field ◽  
Rotational Displacement ◽  
Nonlinear Generalization ◽  
Angle Alpha

AbstractA numerical study of new regimes of reorientation of director field n̂ , velocity v , and components of stress tensor σ_ ij ( ij = x , y , z ) of nematic liquid crystal (LC) encapsulated in a rectangular channel under the action of a strong electric field E directed at angle $$\alpha \left( {\sim\frac{\pi } {2}} \right)$$ α ( ∼ π 2 ) to the horizontal surfaces bounding the LC channel is proposed. The numerical calculations performed in the framework of nonlinear generalization of the classical Eriksen-Leslie theory have shown that at certain relations between the torques and momenta affecting the unit LC volume and E ≫ E _th, transition periodic structures can emerge during reorientation of n̂ , if the corresponding distortion mode has the fastest response, and, thus, suppress all other modes. Rotating domains originating within this process decrease the energy dissipation rate and create more favorable regimes of the director field reorientation, as compared with the uniform rotational displacement.

Radiative Properties of Pattered Wafers With Linewidth Below 100 nm

2005 ◽  
Author(s):  
Y.-B. Chen ◽  
Z. M. Zhang ◽  
P. J. Timans
Keyword(s):  
Periodic Structures ◽  
Numerical Study ◽  
Radiative Properties ◽  
Angle Of Incidence ◽  
Patterned Wafers ◽  
Rigorous Coupled Wave Analysis ◽  
Recent Developments ◽  
Effective Medium Approach ◽  
Rigorous Coupled Wave ◽  
Very High

Temperature nonuniformity is a critical problem in rapid thermal processing (RTP) of wafers because it leads to uneven diffusion of implanted dopants and introduces thermal stress that can produce defects. One cause of the problem is nonuniform absorption of thermal radiation, especially in patterned wafers, where the optical properties vary across the surface of the wafer. Recent developments in RTP have lead to the use of millisecond-duration heating cycles, where light with very high power density is used to heat the surface of the wafer. Pattern effects are especially important here, because there is very little time for thermal diffusion to even out temperature distributions during the heating cycle. There have been very few studies on the radiative properties of patterned wafers, especially for the structures expected to be used on advanced semiconductor devices. The feature size is already below 100 nm and is comparable or smaller than the wavelengths of radiation (200–1000 nm) emitted by the flash-lamps typically used for millisecond processing. Hence, this work is devoted to a parametric numerical study of the radiative properties of patterned wafers with the smallest dimension down to 30 nm. The effects of wavelength, wave polarization, and angle of incidence on selected periodically patterned wafers are presented. The methods include the rigorous coupled wave analysis (RCWA) and the effective medium approach (EMA). RCWA is used to obtain exact solutions of Maxwell’s equations, and EMA is used to approximate the periodic structures as a planar multilayer structure with an effective dielectric function. This study provides an assessment of the applicability of EMA for simulations of radiative properties of patterned wafers.

scholarly journals Numerical Study of Concrete Mesostructure Effect on Lamb Wave Propagation

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2570 ◽  
Author(s):  
Beata Zima ◽  
Rafał Kędra
Keyword(s):  
Particle Size ◽  
Wave Propagation ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Numerical Study ◽  
Diagnostic Methods ◽  
Material Parameters ◽  
The Difference ◽  
Dispersion Solution ◽  
Lamb Wave Propagation

The article presents the results of the numerical investigation of Lamb wave propagation in concrete plates while taking into account the complex concrete mesostructure. Several concrete models with randomly distributed aggregates were generated with the use of the Monte Carlo method. The influence of aggregate ratio and particle size on dispersion curves representing Lamb wave modes was analyzed. The results obtained for heterogeneous concrete models were compared with theoretical results for homogeneous concrete characterized by the averaged macroscopic material parameters. The analysis indicated that not only do the averaged material parameters influence the dispersion solution, but also the amount and size of aggregate particles. The study shows that Lamb waves propagate with different velocities in homogeneous and heterogeneous models and the difference increases with aggregate ratio and particle size, which is a particularly important observation for wave-based diagnostic methods devoted to concrete structures.

scholarly journals 2-D periodic structures. A numerical study

2018 ◽  
Vol 2 (2) ◽  
pp. 175-180
Author(s):  
Giuseppe Rocchetta ◽  
Geminiano Mancusi
Keyword(s):  
Size Effect ◽  
Seismic Isolation ◽  
Mechanical Response ◽  
Periodic Structures ◽  
Numerical Study ◽  
Mass Density ◽  
Band Gaps ◽  
Content Type ◽  
Damping Characteristics ◽  
Lumped Masses

Purpose Within the context of 2D square lattices, searching for the existence of band gaps assumes a great interest owing to many possible fields of application: from energy absorption devices to noise and vibration controllers, as well as advanced strategies for the seismic isolation. Design/methodology/approach The underlying microstructure may influence the mechanical response of 2D square lattices according to a complex interplay between different factors. A first one is related to the so-called “size-effect”. A second one relates, instead, to the mass density distribution. Findings It has been observed that lumped masses may induce additional band gaps to appear and may magnify their width. Finally, an additional factor deals with the inner damping characteristics of the constituent materials, which usually are polymer-based. Originality/value This study focuses on the first factor from a specific perspective: to investigate the influence of the size effect on the existence and properties of frequency band gaps.

scholarly journals The numerical analysis of the interaction between the low-order Lamb wave modes and surface breaking cracks

2019 ◽  
Vol 254 ◽  
pp. 08001 ◽  
Author(s):  
Michal Šofer ◽  
Petr Ferfecki ◽  
Martin Fusek ◽  
Pavel Šofer ◽  
Renata Gnatowska
Keyword(s):  
Lamb Wave ◽  
Guided Waves ◽  
Lamb Waves ◽  
Numerical Study ◽  
Large Structures ◽  
Piping Systems ◽  
Geometric Discontinuities ◽  
Surface Breaking Crack ◽  
Wave Modes ◽  
Low Order

Lamb waves, as one of the types of guided waves, are extensively used for inspecting large structures as well as for structure health monitoring applications. One of the biggest benefits of guided waves is their ability to travel over long distances without much attenuation. Lamb waves are often used for inspection of piping systems and similar geometries where the dimension in the third direction is significantly smaller than the other two. No wonder that the study of the interaction of Lamb waves with particular types of geometric discontinuities is a frequent topic of research. The main aim of the proposed paper is to present the findings related to the numerical study of the interaction between low-order Lamb wave modes and surface breaking crack oriented at different angles relative to the free surface.

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