scholarly journals Postbuckling analyses of frame mesostructures consisting of straight ribbons for mechanically guided three-dimensional assembly

2019 ◽  
Vol 475 (2225) ◽  
pp. 20190012 ◽  
Author(s):  
Yuan Liu ◽  
Zheng Xu ◽  
Keh-Chi Hwang ◽  
Yonggang Huang ◽  
Yihui Zhang
Keyword(s):  
Three Dimensional ◽  
Analytic Solutions ◽  
Finite Element Analyses ◽  
Practical Applications ◽  
Energetic Approach ◽  
Wide Range ◽  
Out Of Plane ◽  
Device Applications ◽  
Theoretical Analyses ◽  
Physical Quantities

Mechanically guided assembly through buckling-induced two-dimensional (2D)-to- three-dimensional (3D) transformation represents a versatile approach to the formation of 3D mesostructures, thanks to the demonstrated applicability to a wide range of length scales (from tens of nanometres to centimetres) and material types (from semiconductors, metals to polymers and ceramics). In many demonstrated examples of device applications, the 2D precursor structures are composed of ribbon-type components, and some of them exhibit frame geometries consisting of multiple straight ribbons. The coupling of bending/twisting deformations among various ribbon components of the frame mesostructures makes the analyses more complicated than the case with a single component, which requires the development of a relevant theory to serve as the basis of design optimization in practical applications. Here, an analytic model of compressive buckling in such frame mesostructures is presented in the framework of energetic approach, taking into account the contributions of spatial bending deformations and twisting deformations. Three different frame geometries are studied, including ‘+’, ‘T' and ‘H' shaped designs. As validated by the experiments and finite-element analyses (FEA), the developed model can predict accurately the assembled 3D configurations during the postbuckling of different precursor shapes. Furthermore, the theoretical analyses provide approximate analytic solutions to some key physical quantities (e.g. the maximum out-of-plane displacements and maximum strains), which can be used as design references in practical applications.

Study of arching behaviour and strength of concrete masonry infills under out-of-plane loading

2019 ◽  
Vol 46 (10) ◽  
pp. 896-908 ◽  
Author(s):  
Ehsan Nasiri ◽  
Yi Liu
Keyword(s):  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Contributing Factors ◽  
Concrete Frames ◽  
Masonry Infills ◽  
Concrete Masonry ◽  
Wide Range ◽  
Out Of Plane ◽  
Three Dimensional Finite Element

A numerical study using a three-dimensional finite element model was conducted to investigate the arching behaviour and strength of concrete masonry infills bounded by reinforced concrete frames subjected to out-of-plane loading. Physical specimens were concurrently tested to provide results for validation of the model as well as evidence of directional characteristics of arching behaviour of masonry infills. A subsequent parametric study using the model included a wide range of infilled frame geometric properties. The results showed in detail the difference in one-way and two-way arching in terms of both strength and failure mechanism, and the contributing factors to this difference. Evaluation of the two main design equations for out-of-plane strength of masonry infills led to proposal of modifications to provide a more rational consideration of directional behaviour of concrete masonry infills. A comparison study using the available test results showed a marked improvement of strength prediction based on the proposed modification.

“Seeing” the Resonant SPP Modes Confined in Metal Nanocavity via Cathodoluminescne Spectroscopy

2014 ◽  
Vol 1659 ◽  
pp. 83-94
Author(s):  
Liu Chuanpu ◽  
Zhu Xinli ◽  
Zhang Jiasen ◽  
Xu Jun ◽  
Yu Dapeng
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polaritons ◽  
Strong Field ◽  
Three Dimensional ◽  
Metal Nanostructures ◽  
Feature Size ◽  
Practical Applications ◽  
Plane Field ◽  
Out Of Plane ◽  
Plasmon Polaritons

ABSTRACT:Surface plasmon polaritons (SPPs), which are coupled excitations of electrons bound to a metal-dielectric interface, show great potential for application in future nanoscale photonic systems due to the strong field confinement at the nanoscale, intensive local field enhancement, and interplay between strongly localized and propagating SPPs. The fabrication of sufficiently smooth metal surface with nanoscale feature size is crucial for SPPs to have practical applications. A template stripping (ST) method combined with PMMA as a template was successfully developed to create extraordinarily smooth metal nanostructures with a desirable feature size and morphology for plasmonics and metamaterials. The advantages of this method, including the high resolution, precipitous top-to bottom profile with a high aspect ratio, and three-dimensional characteristics, make it very suitable for the fabrication of plasmonic structures. By using this ST method, boxing ring-shaped nanocavities have been fabricated and the confined modes of surface plasmon polaritons in these nanocavities have been investigated and imaged by using cathodoluminescence (CL) spectroscopy, which has been turned out to be a powerful means to characterize the resonant SPPs modes confined in metal nanocavities [1∼5] . The mode of the out-of-plane field components of surface plasmon polaritons dominates the experimental mode patterns, indicating that the electron beam locally excites the out-of-plane field component of surface plasmon polaritons. Quality factors can be directly acquired from the spectra induced by the ultrasmooth surface of the cavity and the high reflectivity of the silver (Ag) reflectors. Because of its three-dimensional confined characteristics and the omnidirectional reflectors, the nanocavity exhibits a small modal volume, small total volume, rich resonant modes, and flexibility in mode control. Numerous applications, such as plasmonic filter, nanolaser, and efficient light-emitting devices, can be expected to arise from these developments.

scholarly journals Self-template–assisted micro-phase segregation in blended liquid-crystalline block copolymers films toward three-dimensional structures

2020 ◽  
Vol 117 (35) ◽  
pp. 21070-21078
Author(s):  
Yusuke Hibi ◽  
Yuki Oguchi ◽  
Yuta Shimizu ◽  
Kayoko Hashimoto ◽  
Katsuya Kondo ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Three Dimensional ◽  
Phase Segregation ◽  
Material Design ◽  
The Other ◽  
Cooling Process ◽  
Water Separation ◽  
Practical Applications ◽  
Out Of Plane ◽  
Fundamental Research

In-plane mesopatterns derived from block-copolymer (BCP) micro-phase segregation in thin films have attracted much interest in practical applications as well as fundamental research programs. However, phase segregation along the film-normal direction has been less studied. Here, we describe a strategy to concurrently, yet independently, control in-plane micro-phase and out-of-plane macro-phase segregation in multiblended films composed of liquid-crystalline BCPs (LCBCPs), affording spontaneously layered three-dimensional (3D) mesostructures. This strategy relies on sequential liquid crystallization during the cooling process in thermal annealing as follows. The constituent LCBCP with the highest isotropic-transition temperature (Tiso) first liquid-crystallizes and segregates from the other LCBCP mixture remaining in isotropic states to form a noncontaminated layer at the top surface. This preformed LCBCP layer preserves its inherent in-plane pattern and acts as a template guiding the subsequent micro-phase segregations of the other low-TisoLCBCPs underneath. This self-template–assisted micro-phase segregation (STAMPS) readily provides 3D mesostructures, the potential toward rational material design of which is also demonstrated in water-separation applications.

scholarly journals Generation of highly integrated multiple vivid colours using a three-dimensional broadband perfect absorber

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Soo-Jung Kim ◽  
Pil-Hoon Jung ◽  
Wonjoong Kim ◽  
Heon Lee ◽  
Sung-Hoon Hong
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Perfect Absorber ◽  
Simultaneous Generation ◽  
Practical Applications ◽  
Fabry Perot ◽  
Device Applications ◽  
One Step ◽  
Colour Patterns ◽  
And Control

Abstract The colour printing technology based on interactions between geometric structures and light has various advantages over the pigment-based colour technology in terms of nontoxicity and ultrasmall pixel size. The asymmetric Fabry–Perot (F–P) cavity absorber is the simplest light-interacting structure, which can easily represent and control the colour by the thickness of the dielectric layer. However, for practical applications, an advanced manufacturing technique for the simultaneous generation of multiple reflective colours is required. In this study, we demonstrate F–P cavity absorbers with micropixels by overcoming the difficulties of multi-level pattern fabrication using a nanoimprinting approach. Our asymmetric F–P cavity absorber exhibited a high absorption (approximately 99%) in a wide visible light range upon the incorporation of lossy metallic materials, yielding vivid colours. A high-resolution image of eight different reflective colours was obtained by a one-step process. This demonstrates the potential of this technology for device applications such as high-resolution colour displays and colour patterns used for security functions.

Asymmetric Shielding in Interfacial Fracture Under In-Plane Shear

1992 ◽  
Vol 59 (2) ◽  
pp. 295-304 ◽  
Author(s):  
K. M. Liechti ◽  
Y. S. Chai
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Crack Opening ◽  
Three Dimensional ◽  
Inelastic Behavior ◽  
Finite Element Analyses ◽  
Plane Shear ◽  
Plastic Dissipation ◽  
Wide Range ◽  
Interference Measurements

The toughness of a glass/epoxy interface was measured over a wide range of mode mixes. A toughening effect was associated with increasing positive and negative inplane shear components. Optical interference measurements of normal crack opening displacements near the crack front and complementary finite element analyses were used to examine near-front behavior during crack initiation. Estimates of the toughening based on plastic dissipation, bulk viscoelastic dissipation, and interface asperity shielding did not fully account for the measured values. The results suggest that the inelastic behavior of the epoxy, frictional, and, perhaps, three-dimensional effects should be considered.

Stress Categorization Using the Reference Two-Bar Structure

2007 ◽  
Author(s):  
M. M. Hossain ◽  
R. Adibi-Asl ◽  
R. Seshadri
Keyword(s):  
Finite Element ◽  
Pressure Vessel ◽  
Three Dimensional ◽  
Complex Loading ◽  
Finite Element Analyses ◽  
Number Of Components ◽  
Elastic Stresses ◽  
Linear Elastic ◽  
Geometric Configurations ◽  
Wide Range

The ASME Boiler and Pressure Vessel Codes and Standards used for designing pressure vessel and piping provide guidelines to classify the linear elastic stresses into primary, secondary and peak categories. Although these guidelines cover a wide range of pressure components, they are sometimes difficult to apply to the three-dimensional components with complex loading and geometries. The concept of “reference two-bar structure” is used in this paper to categorize the stresses in pressure components and structures, using linear elastic finite element analyses. The method is applied to a number of components and structures from simple to relatively complex geometric configurations. The results compare well with those obtained from commercial finite element codes.

scholarly journals Analyses of postbuckling in stretchable arrays of nanostructures for wide-band tunable plasmonics

2015 ◽  
Vol 471 (2183) ◽  
pp. 20150632 ◽  
Author(s):  
Yan Shi ◽  
Hongying Luo ◽  
Li Gao ◽  
Cunfa Gao ◽  
John A. Rogers ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Wide Band ◽  
Analytic Solutions ◽  
Applied Strain ◽  
Plasmonic Nanostructures ◽  
Finite Element Analyses ◽  
Nonlinear Transformations ◽  
Buckling Modes ◽  
Photonic Sensors ◽  
Mechanical Tuning

Plasmonic nanostructures integrated with soft, elastomeric substrates provide an unusual platform with capabilities in mechanical tuning of key optical properties, where the surface configurations can undergo large, nonlinear transformations. Arrays of planar plasmonic nanodiscs in this context can, for example, transform into three-dimensional (3D) layouts upon application of large levels of stretching to the substrate, thereby creating unique opportunities in wide-band tunable optics and photonic sensors. In this paper, a theoretical model is developed for a plasmonic system that consists of discrete nanodiscs on an elastomeric substrate, establishing the relation between the postbuckling configurations and the applied strain. Analytic solutions of the amplitude and wavelength during postbuckling are obtained for different buckling modes, which agree well with the results of finite-element analyses and experiment measurements. Further analyses show that increasing the nanodisc distribution yields increased 3D configurations with larger amplitudes and smaller wavelengths, given the same level of stretching. This study could serve as a design reference for future optimization of mechanically tunable plasmonic systems in similar layouts.

Heteroepitaxy on Silicon by Molecular Beam Epitaxy

1988 ◽  
Vol 116 ◽  
Author(s):  
Leo J. Schowalter
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Three Dimensional ◽  
In Situ Observation ◽  
Free Energies ◽  
Practical Applications ◽  
Si Substrates ◽  
Ballistic Electron ◽  
Device Applications ◽  
Heteroepitaxial Layers

AbstractIn recent years extensive research has been conducted on growing heteroepitaxial layers of insulators, metals, and other semiconductors on silicon. This work promises to extend the use of Si (or, at least, Si substrates) far beyond present day devices into hybred semiconductor devices, optoelectronics, ballistic electron devices, and three-dimensional device structures. However, the “art” of heteroepitaxy is still poorly understood and much work remains to be done to realize most practical applications. Molecular beam epitaxy (MBE) represents an attractive technique for research and development of heteroepitaxy because of its relatively low growth temperatures, flexibility in working with different materials, and by providing a good environment for in-situ observation of the heteroepitaxial process. Using examples from recent heteroepitaxial work by molecular beam epitaxy in the areas of CaF2, NiSi2 and CoSi2, and GaAs on Si, this paper discusses how heteroepitaxial quality is affected by the relative surface free energies and strain (due to both lattice and thermal expansion coefficient mismatch). The goal is to produce better heteroepitaxial layers for device applications by an improved understanding of the process.

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