scholarly journals Strain and the optoelectronic properties of nonplanar phosphorene monolayers

2015 ◽  
Vol 112 (19) ◽  
pp. 5888-5892 ◽  
Author(s):  
Mehrshad Mehboudi ◽  
Kainen Utt ◽  
Humberto Terrones ◽  
Edmund O. Harriss ◽  
Alejandro A. Pacheco SanJuan ◽  
...  
Keyword(s):  
Material Properties ◽  
Optoelectronic Properties ◽  
Structural Defects ◽  
Local Geometry ◽  
2D Material ◽  
Unit Cells ◽  
Intimate Relation ◽  
Conical Structure ◽  
Geometrical Effect

Lattice kirigami, ultralight metamaterials, polydisperse aggregates, ceramic nanolattices, and 2D atomic materials share an inherent structural discreteness, and their material properties evolve with their shape. To exemplify the intimate relation among material properties and the local geometry, we explore the properties of phosphorene––a new 2D atomic material––in a conical structure, and document a decrease of the semiconducting gap that is directly linked to its nonplanar shape. This geometrical effect occurs regardless of phosphorene allotrope considered, and it provides a unique optical vehicle to single out local structural defects on this 2D material. We also classify other 2D atomic materials in terms of their crystalline unit cells, and propose means to obtain the local geometry directly from their diverse 2D structures while bypassing common descriptions of shape that are based from a parametric continuum.

Effects of Shear Deformation of Struts in Hexagonal Lattices on their Effective In-Plane Material Properties

2021 ◽  
Vol 1034 ◽  
pp. 193-198
Author(s):  
Pana Suttakul ◽  
Thongchai Fongsamootr ◽  
Duy Vo ◽  
Pruettha Nanakorn
Keyword(s):  
Shear Deformation ◽  
Material Properties ◽  
Strain Energy ◽  
Equivalent Strain ◽  
Homogenization Method ◽  
Two Dimensional ◽  
Engineering Applications ◽  
Large Numbers ◽  
Effective Material Properties ◽  
Unit Cells

Two-dimensional lattices are widely used in many engineering applications. If 2D lattices have large numbers of unit cells, they can be accurately modeled as 2D homogeneous solids having effective material properties. When the slenderness ratios of struts in these 2D lattices are low, the effects of shear deformation on the values of the effective material properties can be significant. This study aims to investigate the effects of shear deformation on the effective material properties of 2D lattices with hexagonal unit cells, by using the homogenization method based on equivalent strain energy. Several topologies of hexagonal unit cells and several slenderness ratios of struts are considered. The effects of struts’ shear deformation on the effective material properties are examined by comparing the results of the present study, in which shear deformation is neglected, with those from the literature, in which shear deformation is included.

Influence of Localized Geometric Imperfections i.e. Buckles and Wrinkles on the Integrity of Pipelines

2008 ◽  
Author(s):  
Zhengmao Yang ◽  
Kumar Shashi ◽  
Jens P. Tronskar
Keyword(s):  
Stress Concentration ◽  
Plastic Strain ◽  
Material Properties ◽  
Fracture Resistance ◽  
Axial Strain ◽  
Compressive Strain ◽  
Mechanical Damage ◽  
Local Deformation ◽  
Local Geometry ◽  
Large Plastic Strain

Pipelines are relied upon to transport hazardous liquids and gasses over long distances. A major threat to the integrity of pipelines is mechanical damage, caused by outside natural forces. According to the AGA report [1], 39% of offshore and 37.7% land based natural gas pipeline failures were caused by outside force. During the installation of offshore pipelines the pipe wall at the 6 o’clock position sees large compressive strain and local buckling may occur. Dents may also occur by impact onto hard objects such as the rollers on the stinger or rocks on the seabed and by anchor impact etc. These kinds of imperfections change the local geometry of the pipe, and therefore, a stress concentration and local bending stress will be induced. The stress concentration factor can be up to 10 depending on the geometry of the imperfection. As a result, the local stresses will be much higher than the design stresses for the pipeline in operation subject to internal pressure and axial strain, and fracture and fatigue capacity of the pipelines with these imperfections will decrease dramatically. Because of the large local deformation, the materials in the deformed pipe region have undergone large local plastic strains i.e. 10–20% plastic deformation. The material properties of the pipe with large plastic strain will be drastically changed, and therefore the fracture resistance of the pipe is expected to be decreased, especially when the damage is located at the seam or girth welds. To assess the criticality of such damage which often can be associated with strain induced flaws in the heavily deformed parent metal and welds, ‘fitness-for-service’ assessment is required. The objective is to determine the severity of the flaws in the deformed pipe and to make the repair/replacement decision. At present there are no definitive assessment guidelines that consider these aspects and how to incorporate the behaviour and fracture capacity of the heavily deformed material. In this paper, a numerical model of typical local imperfections i.e. buckles and wrinkles was established from the in-situ geometry measurements. The local stress distributions of the pipes were analyzed. Based on this stress analyses, the stress concentration around the local imperfections in operation were obtained and the fracture capacity and fatigue life of the pipeline was assessed. The tensile and J R-curve data for deformed pipeline materials were obtained by the DNV Energy laboratory to study the influences of the large plastic strain on the material properties, and the fracture resistance and fatigue crack growth of the pipe. Based on the numerical analysis and test results, a fracture combined fatigue assessment was performed to decide on the mitigation and remediation strategies for the pipeline.

scholarly journals Bio-inspired origami metamaterials with metastable phases through mechanical phase transitions

2021 ◽  
pp. 1-13
Author(s):  
Ke Liu ◽  
Tomohiro Tachi ◽  
Glaucio H. Paulino
Keyword(s):  
Structural Instability ◽  
Two Dimensions ◽  
Important Application ◽  
Metastable Phases ◽  
Design Parameters ◽  
Local Geometry ◽  
Unit Cells ◽  
Geometric Origin ◽  
Wave Guides ◽  
Multi Phase

Abstract Structural instability, once a catastrophic phenomenon to be avoided in engineering applications, is being harnessed to improve functionality of structures and materials, and has catalyzed a substantial research in the field. One important application is to create functional metamaterials that deform their internal structure to adjust performance, resembling phase transformations in natural materials. In this paper, we propose a novel origami pattern, named the Shrimp pattern, with application to multi-phase architected metamaterials whose phase transition is achieve mechanically by snap-through. The Shrimp pattern consists of units that can be easily tessellated in two dimensions, either periodically with homogeneous local geometry, or non-periodically with heterogeneous local geometries. We can use a few design parameters to program the unit cell to become either monostable or bistable, and tune the energy barrier between the bistable states. By tessellating these unit cells into an architected metamaterial, we can create complex yet navigable energy landscape, leading to multiple metastable phases of the material. As each phase has different geometry, the metamaterial can switch between different mechanical properties and shapes. The geometric origin of the multi-stable behavior implies that our designs are scale-independent, making them candidates for a variety of innovative applications, including reprogrammable materials, reconfigurable acoustic wave guides, and microelectronic mechanical systems and energy storage systems.

Design of Miura-Ori Patterns With Acoustic Bandgaps

2017 ◽  
Author(s):  
Phanisri P. Pratapa ◽  
Phanish Suryanarayana ◽  
Glaucio H. Paulino
Keyword(s):  
Wave Propagation ◽  
Material Properties ◽  
Bloch Wave ◽  
Acoustic Metamaterials ◽  
Analysis Framework ◽  
Wave Analysis ◽  
Material Inhomogeneity ◽  
Propagation Behavior ◽  
Unit Cells ◽  
Bloch Wave Analysis

We study the wave propagation behavior in Miura-ori patterns by using the Bloch-wave analysis framework. Our investigation focuses on acoustic bandgaps that act as stopping bands for wave propagation at certain frequencies in periodic solids or structures. We show that bandgaps can be created in two-dimensional periodic Miura-ori patterns by introducing material inhomogeneity. First, we perform Bloch-wave analysis of homogeneous Miura-ori patterns with finite panel rigidity and find that no bandgaps are present. We then introduce bandgaps by making the pattern non-uniform — by changing the mass and axial rigidity of origami panels of alternating unit cells. We discuss the dependence of the magnitude of the bandgap on the contrast between material properties. We find that higher magnitudes of bandgaps are possible by using higher contrast ratios (mass and stiffness). These observations indicate the potential of origami-based patterns to be useful as acoustic metamaterials for vibration control.

A correction for anisotropic line broadening due to structural defects in powder diffraction structure analysis

2000 ◽  
Vol 33 (2) ◽  
pp. 338-343 ◽  
Author(s):  
Leonid A. Solovyov
Keyword(s):  
Structure Analysis ◽  
Powder Diffraction ◽  
Structural Defects ◽  
Line Broadening ◽  
Peak Broadening ◽  
Statistical Consideration ◽  
Unit Cells ◽  
Full Profile ◽  
Consistent Information ◽  
Structure Investigations

An anisotropic line-broadening correction allowing for the presence of structural defects in crystals is developed for powder diffraction full-profile structure analysis. The approach is based on the statistical consideration of diffraction from a crystal composed of two types of unit cells differing in atomic arrangement and/or content, but not in shape and size. The correction is incorporated into a computer program for powder diffraction structural analysis. The application of this correction in crystal structure investigations oftrans- and β-trans-[Pd(NH3)2X2] (X= Cl, Br, I) overcame the problem of selective anisotropic peak broadening and allowed precise and self-consistent information about the structure and the microstructure of these compounds to be obtained.

Regional septal dysfunction in a three-dimensional computational model of focal myofiber disarray

2001 ◽  
Vol 281 (2) ◽  
pp. H506-H514 ◽  
Author(s):  
T. P. Usyk ◽  
J. H. Omens ◽  
A. D. McCulloch
Keyword(s):  
Transgenic Mice ◽  
Material Properties ◽  
Sarcomere Length ◽  
Three Dimensional ◽  
Element Model ◽  
Structural Defects ◽  
Tension Development ◽  
Torsional Shear ◽  
Regional Dysfunction ◽  
Myocyte Disarray

MLC2v/ ras transgenic mice display a phenotype characteristic of hypertrophic cardiomyopathy, with septal hypertrophy and focal myocyte disarray. Experimental measurements of septal wall mechanics in ras transgenic mice have previously shown that regions of myocyte disarray have reduced principal systolic shortening, torsional systolic shear, and sarcomere length. To investigate the mechanisms of this regional dysfunction, a three-dimensional prolate spheroidal finite-element model was used to simulate filling and ejection in the hypertrophied mouse left ventricle with septal disarray. Focally disarrayed septal myocardium was modeled by randomly distributed three-dimensional regions of altered material properties based on measured statistical distributions of muscle fiber angular dispersion. Material properties in disarrayed regions were modeled by decreased systolic anisotropy derived from increased fiber angle dispersion and decreased systolic tension development associated with reduced sarcomere lengths. Compared with measurements in ras transgenic mice, the model showed similar heterogeneity of septal systolic strain with the largest reductions in principal shortening and torsional shear in regions of greatest disarray. Average systolic principal shortening on the right ventricular septal surface of the model was −0.114 for normal regions and −0.065 for disarrayed regions; for torsional shear, these values were 0.047 and 0.019, respectively. These model results suggest that regional dysfunction in ras transgenic mice may be explained in part by the observed structural defects, including myofiber dispersion and reduced sarcomere length, which contributed about equally to predicted dysfunction in the disarrayed myocardium.

Meta-Material Design of the Shear Layer of a Non-Pneumatic Wheel Using Topology Optimization

2012 ◽  
Author(s):  
Christopher Czech ◽  
Paolo Guarneri ◽  
Georges Fadel
Keyword(s):  
Topology Optimization ◽  
Shear Layer ◽  
Material Properties ◽  
Relative Size ◽  
Material Design ◽  
Volume Averaging ◽  
Pneumatic Wheel ◽  
Elastomeric Materials ◽  
Unit Cells ◽  
Homogenization Methods

The meta-material design of the shear layer of a non-pneumatic wheel was completed using topology optimization. In order to reduce the hysteretic rolling loss, an elastic material is used and the shear layer microstructure is defined to achieve high compliance comparable to that offered by the elastomeric materials. To simulate the meta-material properties of the shear layer, the volume averaging analysis, instead of more popular homogenization methods, is used as the relative size of the shear layer places realistic manufacturing constraints on the size of unit cells used to generate the meta-material. In this design scenario the properties predicted by the homogenization methods are not accurate since the homogenization scaling assumptions are violated. A number of optimal designs are shown to have meta-material properties similar to those of the linear elastic properties of elastomers, making them good meta-material candidates for the shear layer of the non-pneumatic wheel.

scholarly journals Influence of Boundary Conditions on the Simulation of a Diamond-Type Lattice Structure: A Preliminary Study

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Patrick Terriault ◽  
Vladimir Brailovski
Keyword(s):  
Boundary Conditions ◽  
Material Properties ◽  
Lattice Structure ◽  
Industrial Applications ◽  
Unit Cell ◽  
Equivalent Material ◽  
Unit Cells ◽  
Type Lattice ◽  
Diamond Type ◽  
Equivalent Material Properties

Emergent additive manufacturing processes allow the use of metallic porous structures in various industrial applications. Because these structures comprise a large number of ordered unit cells, their design using conventional modeling approaches, such as finite elements, becomes a real challenge. A homogenization technique, in which the lattice structure is simulated as a fully dense volume having equivalent material properties, can then be employed. To determine these equivalent material properties, numerical simulations can be performed on a single unit cell of the lattice structure. However, a critical aspect to consider is the boundary conditions applied to the external faces of the unit cell. In the literature, different types of boundary conditions are used, but a comparative study is definitely lacking. In this publication, a diamond-type unit cell is studied in compression by applying different boundary conditions. If the porous structure’s boundaries are free to deform, then the periodic boundary condition is found to be the most representative, but constraint equations must be introduced in the model. If, instead, the porous structure is inserted in a rigid enclosure, it is then better to use frictionless boundary conditions. These preliminary results remain to be validated for other types of unit cells loaded beyond the yield limit of the material.

scholarly journals Super Unit Cells in Aperture-Based Metamaterials

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Dragan Tanasković ◽  
Zoran Jakšić ◽  
Marko Obradov ◽  
Olga Jakšić
Keyword(s):  
Refractive Index ◽  
Optical Transmission ◽  
Negative Refractive Index ◽  
Local Geometry ◽  
Important Class ◽  
Additional Degree ◽  
Spectral Dispersion ◽  
Unit Cells ◽  
Electromagnetic Metamaterials ◽  
Small Additive

An important class of electromagnetic metamaterials are aperture-based metasurfaces. Examples include extraordinary optical transmission arrays and double fishnets with negative refractive index. We analyze a generalization of such metamaterials where a simple aperture is now replaced by a compound object formed by superposition of two or more primitive objects (e.g., rectangles, circles, and ellipses). Thus obtained “super unit cell” shows far richer behavior than the subobjects that comprise it. We show that nonlocalities introduced by overlapping simple subobjects can be used to produce large deviations of spectral dispersion even for small additive modifications of the basic geometry. Technologically, some super cells may be fabricated by simple spatial shifting of the existing photolithographic masks. In our investigation we applied analytical calculations andab initiofinite element modeling to prove the possibility to tailor the dispersion including resonances for plasmonic nanocomposites by adjusting the local geometry and exploiting localized interactions at a subwavelength level. Any desired form could be defined using simple primitive objects, making the situation a geometrical analog of the case of series expansion of a function. Thus an additional degree of tunability of metamaterials is obtained. The obtained designer structures can be applied in different fields like waveguiding and sensing.

Design and analysis of metamaterials for wireless power transfer with same resonance frequency but different L/C combinations

2020 ◽  
Vol 64 (1-4) ◽  
pp. 377-384
Author(s):  
Wenjia Yang ◽  
S.L. Ho ◽  
W.N. Fu ◽  
Shiyou Yang
Keyword(s):  
Robust Design ◽  
Material Properties ◽  
Power Transmission ◽  
Operating Conditions ◽  
Wireless Power ◽  
Two Phase ◽  
Analysis And Design ◽  
Unique Material ◽  
Unit Cells ◽  
Conventional Material

Metamaterial is an artificial material with unique material properties that cannot be found in a naturally existing one, and hence it is able to perform functions that a conventional material cannot do. Consequently, it has shown great potential in various engineering applications such as resonance coupled mid-range wireless power transmission (R-WPT) systems. However, the analysis and design of an application-oriented metamaterial include both the unit cells and their combinations, and thus are very complex. Moreover, the performance of a metamaterial is very sensitive to uncertainties in both manufacturing and operating conditions. In this regard, a two-phase methodology for robust design optimizations of metamaterial slabs in R-WPT applications is proposed and applied to the design optimization of a prototype R-WPT system with promising results.

Sign in / Sign up

Export Citation Format

Share Document