Rheo-Optics Studies in the Development of Hybrid Liquid Crystalline Based Mwir Polarizers

1999 ◽  
Vol 559 ◽  
Author(s):  
P.T. Mather ◽  
W. Barnes ◽  
P.J. Hood ◽  
T.J. Bunning
Keyword(s):  
Liquid Crystalline ◽  
Flow Behavior ◽  
Optical Microscope ◽  
Processing Technique ◽  
Strain Rates ◽  
Alignment Layer ◽  
Small Pitch ◽  
Wide Range ◽  
Measured Polarization ◽  
Free Films

ABSTRACTWe present here a rheo-optical study of the flow behavior of two cholesteric liquid crystals, one with a large pitch and one with a small pitch. The large pitch compound has been investigated as a possible fixed wavelength polarizer in the mid-wavelength infra-red region (3-5 micron). The investigation of these compounds is driven by their low melt viscosity and ability to vitrify order, and thus functionality, into films with a wide range of thickness. In our attempts to obtain consistent thin films with reproducible contrast ratios, we explored the defect textures of both compounds under a polarizing optical microscope. These materials were sheared at various strain rates and at various temperatures in an attempt to determine the best processing window for defect free films. The pitch lengths of the two materials investigated were 160 and 1330 nm. The flow behavior of the large pitch material resembles a pure nematic with defect refinement taking place under flow. The short pitch material exhibited the typical Grandjean oily streaks upon shearing followed by coarsening. Observations made during this rheological study were used to identify a processing technique for the large pitch materials. Upon application of a conventional buffed alignment layer, films with consistent quality were routinely made. The measured polarization contrast of >70:1 exceeds the values obtained from state-of-the art commercial polarizers in this wavelength regime.

Modeling of flow behavior for 7050-T7451 aluminum alloy considering microstructural evolution over a wide range of strain rates

2016 ◽  
Vol 95 ◽  
pp. 146-157 ◽  
Author(s):  
Guang Chen ◽  
Chengzu Ren ◽  
Zhihong Ke ◽  
Jun Li ◽  
Xinpeng Yang
Keyword(s):  
Aluminum Alloy ◽  
Microstructural Evolution ◽  
Flow Behavior ◽  
Strain Rates ◽  
Wide Range

A Mathematical Description for the Stress-Strain Behavior of Annealed 2 1/4 Cr-1 Mo Steel

1976 ◽  
Vol 98 (2) ◽  
pp. 118-125 ◽  
Author(s):  
R. L. Klueh ◽  
T. L. Hebble
Keyword(s):  
Mathematical Description ◽  
Flow Behavior ◽  
True Strain ◽  
Empirical Relationship ◽  
Tensile Tests ◽  
Strain Rates ◽  
Strain Behavior ◽  
Test Conditions ◽  
Wide Range ◽  
Strain Data

We have conducted a detailed series of tensile tests on one heat of annealed 2 1/4 Cr-1 Mo steel over the range 25 to 593°C (75 to 1100°F) and at nominal strain rates of 0.4, 0.04, 0.004, and 0.0004/min. To determine an empirical relationship to represent the flow behavior, we fitted the true-stress true-strain data from these tests to several proposed models. The models fit were those proposed by Hollomon, Ludwik, Ludwigson, and Voce. From a comparison of the standard error of estimate, the Voce equation was concluded to be the best mathematical description of the data under most test conditions and the best single representation over the wide range of test conditions.

Prediction of Flow Stress for Superplastic Tension Deformation

2014 ◽  
Vol 941-944 ◽  
pp. 1501-1504
Author(s):  
Zhi Ping Guan ◽  
Ming Wen Ren ◽  
Pin Kui Ma ◽  
Po Zhao
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Flow Behavior ◽  
High Accuracy ◽  
Superplastic Flow ◽  
Al Alloy ◽  
Strain Rates ◽  
Good Reliability ◽  
Wide Range

With the development of numerical calculation and precision forming, constitutive equations are required to possess high accuracy and good reliability, rather than simplicity of mathematical form. Due to simple algorithm and constant parameters, the conventional constitutive models can not be suited to describing superplastic flow behavior which represents complex responses with a large strain. In this study, through surface fitting on experimental data from tension tests performed over a wide range of strain rates, tensile velocities and loads, an empirical approach was proposed to establish constitutive equation for complex superplastic behavior of Zn-5%Al alloy at 340 °C. The empirical constitutive equation not only represents the strain dependence and the strain rate dependence of stress, but also reflects the coupling effects of strain and strain rate on stress, which can not be achieved by traditional models. A comparison between the predicted flow stresses and the experimental data verified that the empirical constitutive equation has high accuracy and good reliability on modeling superplastic flow behavior of Zn-5%Al alloy at 340 °C in a wide range of strains 0~2.5 and strain rates 7.0×10-5~8.0×10-2s-1.

Constitutive Modeling for Superplastic Flow Behavior of H62 Alloy

2014 ◽  
Vol 941-944 ◽  
pp. 1488-1491
Author(s):  
Zhi Ping Guan ◽  
Hong Jie Jia ◽  
Ming Wen Ren ◽  
Dong Lai Wei
Keyword(s):  
Experimental Data ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Flow Behavior ◽  
Constant Strain Rate ◽  
Superplastic Flow ◽  
Strain Rates ◽  
Good Ability ◽  
Wide Range ◽  
Comprehensive Reliability

In order to precisely describe superplastic flow behavior of H62 alloy, a empirical constitutive equation was established based on the experimental data, which were obtained from the constant strain rate tensions (2.0×10-4~4.0×10-2s-1) at 720 °C. Through verification of the constitutive equation with the experimental data in constant strain rate tensions and constant velocity tensions, it was indicated that the empirical constitutive equation has high accuracy and comprehensive reliability in a wide range of strain rates (2.0×10-4~2.0×10-2s-1) and strains (0~1.8). In addition, the empirical constitutive equation has a good ability to model the superplastic flow behavior of H62 alloy at 720 °C under other deformation conditions besides constant strain rate tension.

Constitutive flow behavior of IFAC-1 austenitic stainless steel depicting strain saturation over a wide range of strain rates and temperatures

2014 ◽  
Vol 56 ◽  
pp. 565-571 ◽  
Author(s):  
Dipti Samantaray ◽  
Alpesh Patel ◽  
Utpal Borah ◽  
S.K. Albert ◽  
A.K. Bhaduri
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Flow Behavior ◽  
Strain Rates ◽  
Wide Range

Flow behavior of diffusion bonding interface of Ti6Al4V alloy over a wide range of strain rates

2019 ◽  
Vol 761 ◽  
pp. 138067 ◽  
Author(s):  
Huiping Wu ◽  
Xifeng Li ◽  
Qiongfeng Mei ◽  
Jun Chen ◽  
Guohong Wu
Keyword(s):  
Diffusion Bonding ◽  
Flow Behavior ◽  
Ti6al4v Alloy ◽  
Bonding Interface ◽  
Strain Rates ◽  
Wide Range

Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

1993 ◽  
Vol 51 ◽  
pp. 884-885
Author(s):  
David M. Anderson ◽  
Tomas Landh
Keyword(s):  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Cubic Phase ◽  
List Type ◽  
Interpenetrating Networks ◽  
Triply Periodic ◽  
Wide Range ◽  
Bicontinuous Cubic ◽  
Phase Liquid ◽  
Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

URBAN FACADE GEOMETRY ON OUTDOOR COMFORT CONDITIONS: A REVIEW

2020 ◽  
Vol 4 (1) ◽  
pp. 45
Author(s):  
Elahe Mirabi ◽  
Nasrollahi Nazanin
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Natural Ventilation ◽  
Flow Behavior ◽  
Air Flow ◽  
Urban Geometry ◽  
Wide Range ◽  
Low Energy Buildings ◽  
Outdoor Comfort ◽  
Solar Access

<p>Designing urban facades is considered as a major factor influencing issues<br />such as natural ventilation of buildings and urban areas, radiations in the<br />urban canyon for designing low-energy buildings, cooling demand for<br />buildings in urban area, and thermal comfort in urban streets. However, so<br />far, most studies on urban topics have been focused on flat facades<br />without details of urban layouts. Hence, the effect of urban facades with<br />details such as the balcony and corbelling on thermal comfort conditions<br />and air flow behavior are discussed in this literature review. <strong>Aim</strong>: This<br />study was carried out to investigate the effective factors of urban facades,<br />including the effects of building configuration, geometry and urban<br />canyon’s orientation. <strong>Methodology and Results</strong>: According to the results,<br />the air flow behavior is affected by a wide range of factors such as wind<br />conditions, urban geometry and wind direction. Urban façade geometry<br />can change outdoor air flow pattern, thermal comfort and solar access.<br /><strong>Conclusion, significance and impact study</strong>: In particular, the geometry of<br />the facade, such as indentation and protrusion, has a significant effect on<br />the air flow and thermal behavior in urban facades and can enhance<br />outdoor comfort conditions. Also, Alternation in façade geometry can<br />affect pedestrians' comfort and buildings energy demands.</p>

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