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Stretching Parameter (stretching + parameter)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Numerical study of grid distribution effect on accuracy of DQ analysis of beams and plates by error estimation of derivative approximation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2001
C. Shu
Abstract The accuracy of global methods such as the differential quadrature (DQ) approach is usually sensitive to the grid point distribution. This paper is to numerically study the effect of grid point distribution on the accuracy of DQ solution for beams and plates. It was found that the stretching of grid towards the boundary can improve the accuracy of DQ solution, especially for coarse meshes. The optimal grid point distribution (corresponding to optimal stretching parameter) depends on the order of derivatives in the boundary condition and the number of grid points used. The optimal grid distribution may not be from the roots of orthogonal polynomials. This differs somewhat from the conventional analysis. This paper also proposes a simple and effective formulation for stretching the grid towards the boundary. The error distribution of derivative approximation is also studied, and used to analyze the effect of grid point distribution on accuracy of numerical solutions. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Characterization of Electrical Properties of Li(FexAl1,x)5O8 Solid Solutions by Impedance Spectroscopy

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000
Shuichi Arakawa
To examine polaronic transport properties in Li(FexAl1,x)5O8 spinel solid solutions, a scaling analysis for their conductivity spectra and modulus spectra was performed. As in the case of ionic conductors, two significant parameters of a crossover frequency and a power-law exponent were extracted from the conductivity spectra which displayed the universal dynamic response behavior. Both the mobility and the concentration of carriers were successfully determined from the crossover frequency. The power-law exponent and the stretching parameter obtained from the modulus spectra varied with composition, implying that the increase in Fe concentration would enhance the Coulomb interactions between small polarons. [source]

Studies on , to , phase transformations in mechanically deformed PVDF films

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Vijayakumar R. P.
Abstract PVDF cast films were drawn at different temperatures to different draw ratios at constant draw rate to understand the mechanism of , to , phase transformation during mechanical deformation. WAXD and FTIR studies were carried out to determine the formation and content of , phase in the drawn films. Lower stretch temperatures gave higher fractions of , phase. The cast PVDF films were also drawn at suitable temperatures below the PVDF ambient melting point to the draw ratio of 6.4. The highest fraction of , phase obtained in these ultra drawn films was 0.98. SALS studies carried out for films at different stretch ratios show the change in spherulitic structure with the stretching parameters and give information for the understanding of phase transformation during stretching of PVDF films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Properties and strain hardening character of polyethylene terephthalate containing Isosorbide

POLYMER ENGINEERING & SCIENCE, Issue 3 2009
Ramesh M. Gohil
Polyethylene terephthalate containing Isosorbide (PEIT) polymers made from renewable corn-derived Isosorbide monomer exhibit a wide range of glass transition temperatures (80,180°C) and are therefore able to be used in many applications. Stress,strain curves for high Isosorbide content copolymers show strain softening, which impairs the molecular orientation during orientation of films and bottles. It is therefore necessary to find ways to modify deformation behavior of PEIT copolymers. Deformation characteristics of PEIT and other polyesters have been evaluated to define stretching parameters and necessary composition for making oriented bottles for hot fill applications. In the presence of polymeric nucleating agents, (polymeric ionomers or polyesters containing sodium ions), strain-hardening parameters become almost temperature- independent below solid state deformation temperature of 125°C. We developed a methodology to achieve molecular orientation comparable with films and articles made by conventional processing of poly(ethylene terephthalate), PET. Polyesters containing sodium ions are efficient nucleating agents for PEIT, and their required concentration is dependent on deformation temperature. Both strain hardening and stress at 250% strain depend on the concentration of nucleating agents and deformation temperatures. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]