scholarly journals Lorentz resonance in the homogenization of plasmonic crystals

2021 ◽  
Vol 477 (2256) ◽  
Author(s):  
W. Li ◽  
R. Lipton ◽  
M. Maier
Keyword(s):  
Material Properties ◽  
Graphene Nanosheets ◽  
Small Scale ◽  
Surface Conductance ◽  
Dielectric Tensor ◽  
Heterogeneous Structure ◽  
Computational Tool ◽  
Surface Geometry ◽  
Plasmonic Crystals ◽  
General Frequency

We explain the Lorentz resonances in plasmonic crystals that consist of two-dimensional nano-dielectric inclusions as the interaction between resonant material properties and geometric resonances of electrostatic nature. One example of such plasmonic crystals are graphene nanosheets that are periodically arranged within a non-magnetic bulk dielectric. We identify local geometric resonances on the length scale of the small-scale period. From a materials perspective, the graphene surface exhibits a dispersive surface conductance captured by the Drude model. Together these phenomena conspire to generate Lorentz resonances at frequencies controlled by the surface geometry and the surface conductance. The Lorentz resonances found in the frequency response of the effective dielectric tensor of the bulk metamaterial are shown to be given by an explicit formula, in which material properties and geometric resonances are decoupled. This formula is rigorous and obtained directly from corrector fields describing local electrostatic fields inside the heterogeneous structure. Our analytical findings can serve as an efficient computational tool to describe the general frequency dependence of periodic optical devices. As a concrete example, we investigate two prototypical geometries composed of nanotubes and nanoribbons.

Mechanical Behavior of Functionally Graded Nano-Cylinders Under Radial Pressure Based on Strain Gradient Theory

2018 ◽  
Vol 35 (4) ◽  
pp. 441-454 ◽  
Author(s):  
M. Shishesaz ◽  
M. Hosseini
Keyword(s):  
Mechanical Behavior ◽  
Strain Gradient ◽  
Material Properties ◽  
Scale Effects ◽  
Radial Pressure ◽  
Functionally Graded ◽  
High Order ◽  
Strain Gradient Theory ◽  
Small Scale ◽  
Gradient Theory

ABSTRACTIn this paper, the mechanical behavior of a functionally graded nano-cylinder under a radial pressure is investigated. Strain gradient theory is used to include the small scale effects in this analysis. The variations in material properties along the thickness direction are included based on three different models. Due to slight variations in engineering materials, the Poisson’s ratio is assumed to be constant. The governing equation and its corresponding boundary conditions are obtained using Hamilton’s principle. Due to the complexity of the governed system of differential equations, numerical methods are employed to achieve a solution. The analysis is general and can be reduced to classical elasticity if the material length scale parameters are taken to be zero. The effect of material indexn, variations in material properties and the applied internal and external pressures on the total and high-order stresses, are well examined. For the cases in which the applied external pressure at the inside (or outside) radius is zero, due to small effects in nano-cylinder, some components of the high-order radial stresses do not vanish at the boundaries. Based on the results, the material inhomogeneity indexn, as well as the selected model through which the mechanical properties may vary along the thickness, have significant effects on the radial and circumferential stresses.

STYLE: Study on Transferability of Fracture Material Properties From Small Scale Specimens to a Real Component

2011 ◽  
Author(s):  
Tomas Nicak ◽  
Herbert Schendzielorz ◽  
Elisabeth Keim ◽  
Gottfried Meier
Keyword(s):  
Fracture Mechanics ◽  
Material Properties ◽  
Large Scale ◽  
Fracture Behaviour ◽  
Experimental Investigations ◽  
Small Scale ◽  
Real Component ◽  
Material Data ◽  
Analytical Work ◽  
Constraint Effects

This paper describes numerical and experimental investigations on transferability of material properties obtained by testing of small scale specimens to a real component. The presented study is related to the experimental and analytical work performed on Mock-up3, which is one of three unique large scale Mock-ups tested within the European project STYLE. Mock-up3 is foreseen to investigate transferability of material data, in particular fracture mechanics properties. An important part of this work is to study constraint effects on different small scale specimens and to compare their fracture behaviour with the fracture behaviour of a large scale (component like) structure. The Mock-Up3 is an original part of a surge line made of low alloy steel 20 MnMoNi 5 5 (which corresponds to SA 508 Grade 3, Cl. 1). The goal of the test is to introduce stable crack growth of an inner surface flaw until a break through the wall occurs. To design such a test reliable fracture mechanics material properties must be available. Usually, these material data are obtained by testing small specimens, which are subsequently used for the assessment of a large scale structure (component). This is being done under the assumption that these “small scale” material properties are fully transferable to “large scale” components. It is assumed that crack initiation in the ductile tearing regime is rather independent of the crack shape, a/W ratio, loading condition or size of the specimen (constraint effects). In order to check the aforementioned assumption and to improve understanding of the physical process leading to failure of cracked components comprehensive experimental and analytical work is being undertaken in STYLE. This paper summarizes Up-To-Date available results, which have been achieved during the first 15 months of the project.

A Molecular Model of Asperity Contact and Comparison to Continuum Based Models

2008 ◽  
Author(s):  
Wei Huang ◽  
Robert L. Jackson
Keyword(s):  
Contact Mechanics ◽  
Continuum Mechanics ◽  
Material Properties ◽  
Molecular Model ◽  
Small Scale ◽  
Elastic Contact ◽  
Asperity Contact ◽  
Molecular Forces ◽  
The Continuum

Surface asperities can range widely in size. Therefore it is important to characterize the effect of size and scale on the contact mechanics. This work presents a molecular model of asperity contact in order to characterize small scale asperity contact. The model is also compared to existing continuum mechanics based models developed originally by Hertz for elastic contact and later expanded by others to include plasticity. It appears that the predictions can be related to each other and that the continuum material properties can be related to the properties describing the molecular forces.

scholarly journals Flutter and Divergence Instability of Axially-Moving Nanoplates Resting on a Viscoelastic Foundation

2019 ◽  
Vol 9 (6) ◽  
pp. 1097 ◽  
Author(s):  
Jingbo Duan ◽  
Dapeng Zhang ◽  
Wenjie Wang
Keyword(s):  
Graphene Nanosheets ◽  
Viscoelastic Behavior ◽  
Nonlocal Elasticity Theory ◽  
Small Scale ◽  
Complex Frequency ◽  
Viscoelastic Foundation ◽  
Viscoelastic Parameters ◽  
Axial Forces ◽  
Divergence Instability ◽  
Axially Moving

Moving nanosystems often rest on a medium exhibiting viscoelastic behavior in engineering applications. The moving velocity and viscoelastic parameters of the medium usually have an interacting impact on the mechanical properties of nanostructures. This paper investigates the dynamic stability of an axially-moving nanoplate resting on a viscoelastic foundation based on the nonlocal elasticity theory. Firstly, the governing partial equations subject to appropriate boundary conditions are derived through utilizing the Hamilton’s principle with the axial velocity, viscoelastic foundation, nonlocal effect and biaxial loadings taken into consideration. Subsequently, the characteristic equation describing the dynamic characteristics is obtained by employing the Galerkin strip distributed transfer function method. Then, complex frequency curves for the nanoplate are displayed graphically and the effects of viscoelastic foundation parameters, small-scale parameters and axial forces on divergence instability and coupled-mode flutter are analyzed, which show that these parameters play a crucial role in affecting nanostructural instability. The presented results benefit the designation of axially-moving graphene nanosheets or other plate-like nanostructures resting on a viscoelastic foundation.

scholarly journals Effect of Axial Porosities on Flexomagnetic Response of In-Plane Compressed Piezomagnetic Nanobeams

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 1935 ◽  
Author(s):  
Mohammad Malikan ◽  
Victor A. Eremeyev ◽  
Krzysztof Kamil Żur
Keyword(s):  
Material Properties ◽  
Gradient Elasticity ◽  
Small Scale ◽  
Stability Equation ◽  
Strain Gradients ◽  
Size Dependent ◽  
Different Types ◽  
Dependent Property ◽  
The Stability ◽  
Transverse Deflection

We investigated the stability of an axially loaded Euler–Bernoulli porous nanobeam considering the flexomagnetic material properties. The flexomagneticity relates to the magnetization with strain gradients. Here we assume both piezomagnetic and flexomagnetic phenomena are coupled simultaneously with elastic relations in an inverse magnetization. Similar to flexoelectricity, the flexomagneticity is a size-dependent property. Therefore, its effect is more pronounced at small scales. We merge the stability equation with a nonlocal model of the strain gradient elasticity. The Navier sinusoidal transverse deflection is employed to attain the critical buckling load. Furthermore, different types of axial symmetric and asymmetric porosity distributions are studied. It was revealed that regardless of the high magnetic field, one can realize the flexomagnetic effect at a small scale. We demonstrate as well that for the larger thicknesses a difference between responses of piezomagnetic and piezo-flexomagnetic nanobeams would not be significant.

Basic Polymer Material Properties for Flame Spread

1993 ◽  
Vol 11 (4) ◽  
pp. 287-295 ◽  
Author(s):  
M.A. Delichatsios
Keyword(s):  
Flame Spread ◽  
Material Properties ◽  
Oxygen Index ◽  
Fire Hazard ◽  
Fire Spread ◽  
Test Methods ◽  
Critical Conditions ◽  
Small Scale ◽  
Limited Oxygen Index ◽  
Limited Oxygen

We present and demonstrate the application of a systematic methodology for predicting fire spread and growth and for a relative fire hazard classification of materials for any scale and fire environment. This methodol ogy consists of three steps: (1) select laboratory test methods to perform flam mability measurements; (2) based on these measurements, obtain key flamma bility material properties which are precisely defined in this work; and (3) use these properties in a mathematical model of fire spread and growth to predict fire hazards. The complementary test methods we have selected and used are: (a) a general flammability test apparatus (such as NIST or FMRC) [1,2] modified to also provide pyrolysis measurements in an inert N2 atmosphere; (b) the Limited Oxygen Index (LOI) apparatus, which is used here as a tool for ob taining properties needed for creeping flame spread and extinction, including vitiated environments; and (c) a solid material smoke-point height apparatus [8], which is used to characterize the smokiness of the burning material needed to determine the radiation and smoke yield for arbitrary fire situations (wall fires, pool fires or ceiling fires) [8]. The use and proper interpretation of the Limited Oxygen Index apparatus can replace the LIFT [10] apparatus for deter mining in a more accurate and direct way the material properties required for creeping (vertical downward, lateral, horizontal) flame spread. The present methodology has been compared well with experiments in this work and else where [9], and it has been used to predict critical conditions for fire spread [11], not empirically as it is usually done, but based on first principles of fire spread, fire growth and burning, together with material flammability properties syste matically deduced from small-scale test measurements.

Effects of Freeze-Thaw Cycling on Material Properties of Cancellous Cervine Bone as Characterized by Nanoindentation

2013 ◽  
Author(s):  
Alexander K. Landauer ◽  
Philip A. Yuya ◽  
Laurel Kuxhaus
Keyword(s):  
Material Properties ◽  
Applied Load ◽  
Dynamic Testing ◽  
Small Scale ◽  
Phase Lag ◽  
Static Force ◽  
Cross Sectional ◽  
Freeze Thaw ◽  
Material Parameters ◽  
Storage And Loss Moduli

Cancellous bone is an important load-bearing component of whole bone, and due to the plate-and-rod nature of trabeculae, small-scale testing is required to measure material parameters for use in modern analytic techniques such as finite element modeling [1, 2]. These material properties are measurable via nanoindentation techniques. During nanoindentation, the indenter tip is forced into the surface of the material while the applied load and tip displacement are monitored. Using these data, along with the tip’s cross-sectional area, mechanical properties are determined. Dynamic testing quantifies viscoelastic response and can obtain material response parameters such as storage and loss moduli. During dynamic testing, a low magnitude sinusoidal force is superimposed on a constant static force. The displacement response is measured at the same frequency as the applied oscillating force, and the resulting phase lag is related to material damping [3].

A Mesoscale Data Analysis and Downscaling Method over Complex Terrain

2006 ◽  
Vol 134 (10) ◽  
pp. 2758-2771 ◽  
Author(s):  
Reinhold Steinacker ◽  
Matthias Ratheiser ◽  
Benedikt Bica ◽  
Barbara Chimani ◽  
Manfred Dorninger ◽  
...  
Keyword(s):  
Data Analysis ◽  
Pressure Field ◽  
Spline Interpolation ◽  
A Priori ◽  
Small Scale ◽  
Mountain Range ◽  
Surface Geometry ◽  
Dynamic Surface ◽  
Reduced Pressure ◽  
Thermally Induced

Abstract A mesoscale data analysis method for meteorological station reports is presented. Irregularly distributed measured values are combined with measurement-independent a priori information about the modification of analysis fields due to topographic forcing. As a physical constraint to a thin-plate spline interpolation, the so-called “fingerprint method” recognizes patterns of topographic impact in the data and allows for the transfer of information to data-sparse areas. The results of the method are small-scale interpolation fields on a regular grid including topographically induced patterns that are not resolved by the station network. Presently, the fingerprint method is designed for the analysis of scalar meteorological variables like reduced pressure or air temperature. The principles for the fingerprint technique are based on idealized influence fields. They are calculated for thermal and dynamic surface forcing. For the former, the effects of reduced air volumes in valleys, the elevated heat sources, and the stability of the valley atmosphere are taken into account. The increase of temperature under ideal conditions in comparison to flat terrain is determined on a 1-km grid using height and surface geometry information. For the latter, a perturbation of an originally constant cross-Alpine temperature gradient is calculated by a topographical weighting. As a result, the gradient is steep where the mountain range is high and steep. If, during the interpolation process, some signal of the idealized patterns is found in the station data, it is used to downscale the analysis. It is shown by a cross validation of a case study that the interpolation of a mean sea level pressure field over the Alpine region is improved objectively by the method. Thermally induced mesoscale patterns are visible in the interpolated pressure field.

STYLE: Transferability of Fracture Material Properties - Updated Experimental and Analytical Results

2012 ◽  
Author(s):  
Tomas Nicak ◽  
Herbert Schendzielorz ◽  
Elisabeth Keim ◽  
Gottfried Meier ◽  
Dominique Moinereau ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Material Properties ◽  
Large Scale ◽  
Small Scale ◽  
Outer Diameter ◽  
Real Component ◽  
Material Data ◽  
Analytical Results ◽  
Grade 3 ◽  
Original Part

This paper describes new results of the STYLE study on investigations of transferability of fracture material properties obtained by testing of small scale specimens to a real component. In STYLE there are three large scale mock-up tests each of them dedicated to investigate specific effects. Mock-up3 (cladded ferritic pipe with the outer diameter of 424 mm) is foreseen to investigate transferability of material data, in particular to compare fracture mechanics behavior of small specimens under different constraint conditions with a full size component. The Mock-Up3 is an original part of a surge line made of low alloy steel (20MnMoNi55 which corresponds to SA 508 Grade 3, Cl. 1). Usually, material data necessary for fracture mechanic analyses are obtained by testing small specimens, which are subsequently used for the assessment of large scale structures (real components). This approach is believed to be conservative since the material properties are obtained on highly constrained standard specimens. In this paper new experimental and analytical results will be presented (including tests on constraint modified specimens and a comparison of these results with the Mock-up3 test). The overall objective is to investigate the influence of specimen size, crack shape and type of loading on fracture mechanics properties like crack initiation load or amount of the crack growth by means of numerical analyses and compared with experimental results.

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