A Critical Analysis of Using Step-Strain and Extensional Rheology to Obtain the Multi-mode “Pom-Pom” Model Parameters for Branched High-Density Polyethylenes

2008 ◽  
Author(s):  
Christopher D. McGrady ◽  
Christopher W. Seay ◽  
Donald G. Baird ◽  
Dietmar Auhl ◽  
Tom C. McLeish ◽  
...  
Keyword(s):  
Critical Analysis ◽  
High Density ◽  
Model Parameters ◽  
Extensional Rheology ◽  
Multi Mode ◽  
Step Strain

Shear Deformation of High Density Aluminum Honeycombs

2003 ◽  
Author(s):  
Wei-Yang Lu ◽  
John Korellis ◽  
Terry Hinnerichs
Keyword(s):  
Shear Deformation ◽  
Shear Test ◽  
High Density ◽  
Model Parameters ◽  
Test Beam ◽  
Model Simulations ◽  
Aluminum Honeycomb ◽  
Axis Compression ◽  
Principal Directions ◽  
Flexure Test

The orthotropic crush model has commonly been used to describe the constitutive behavior of honeycomb [1]. To completely define the model parameters of a honeycomb, experimental data of axial crushes in T, L, and W principal directions as well as shear stress-strain curves in TL, TW, and LW planes are required. The axial crushes of high-density aluminum honeycombs, e.g., 38 pcf (pound per cubic foot), under various loading speeds and temperatures have been investigated and reported [2]. This paper describes experiments and model simulations of the shear deformation of the same high-density aluminum honeycomb. Results of plate shear test, beam flexure test, and off-axis compression are presented and discussed.

scholarly journals NL Model on Traffic Mode Split among High-Density Town Cluster

2012 ◽  
Vol 5 ◽  
pp. 99-104 ◽  
Author(s):  
Shi Mei Wu ◽  
Yu Long Pei
Keyword(s):  
High Speed ◽  
High Density ◽  
Urban Rail Transit ◽  
Rail Transit ◽  
Aggregate Model ◽  
High Speed Rail ◽  
Mode Split ◽  
Urban Rail ◽  
Disaggregate Model ◽  
Multi Mode

With urbanization process acceleration in China, traffic travel among cities becomes increasing, and traffic mode split is the key link of traffic passenger flow forecast among cities. In this paper, the concept of high-density town cluster was proposed to analyze the characteristics of development, population composition, and traffic facilities among high-density town cluster. Based on applicability analysis of aggregate model and disaggregate model, survey content of revealed preference (RP) and stared preference (SP), and traffic mode hierarchical division according to average speed, then NL disaggregate model among high-density town cluster was constructed. NL model which was parameter calibrated and validated with DongGuan citizen travel investigation data in 2009 was used to analyze the trend of traffic mode split. The result shows that high-density town cluster, such as DongGuan, are establishing a three-dimensional travel mode set, including high-speed rail, intercity rail, suburban rail, urban rail transit, intercity express bus, car, taxi, and common public transport. With the network of multi-mode rail transit further improving, ratio on choosing the traffic mode of multi-mode rail transit, such as high-speed rail, intercity rail, suburban rail, urban rail transit, increases dramatically.

scholarly journals Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3217
Author(s):  
Leslie Poh ◽  
Esmaeil Narimissa ◽  
Manfred H. Wagner
Keyword(s):  
Stress Function ◽  
High Density Polyethylene ◽  
High Density ◽  
Molecular Characteristics ◽  
Chain Branching ◽  
Data Set ◽  
Long Chain Branching ◽  
Molecular Stress Function ◽  
Multi Mode ◽  
Long Chain

The transient elongational data set obtained by filament-stretching rheometry of four commercial high-density polyethylene (HDPE) melts with different molecular characteristics was reported by Morelly and Alvarez [Rheologica Acta 59, 797–807 (2020)]. We use the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model of Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheology 60, 625–636 (2016)] for linear and long-chain branched (LCB) polymer melts to analyze the extensional rheological behavior of the four HDPEs with different polydispersity and long-chain branching content. Model predictions based solely on the linear-viscoelastic spectrum and a single nonlinear parameter, the dilution modulus GD for extensional flows reveals good agreement with elongational stress growth data. The relationship of dilution modulus GD to molecular characteristics (e.g., polydispersity index (PDI), long-chain branching index (LCBI), disengagement time τd) of the high-density polyethylene melts are presented in this paper. A new measure of the maximum strain hardening factor (MSHF) is proposed, which allows separation of the effects of orientation and chain stretching.

Crush of High Density Aluminum Honeycombs

2001 ◽  
Author(s):  
Wei-Yang Lu ◽  
Terry Hinnerichs
Keyword(s):  
Principal Direction ◽  
High Density ◽  
Model Parameters ◽  
Compression Tests ◽  
Confined Compression ◽  
Strain Behavior ◽  
Rate Effects ◽  
Global Buckling ◽  
Deformation Modes ◽  
Crush Strength

Abstract The orthotropic crush model has commonly been used to describe the stress-strain behavior of honeycomb. Important model parameters include crush strength and crush efficiency of each principal direction. Experiments were conducted to obtain these model parameters of high-density honeycombs. Various deformation modes were observed during “bare” compression tests. The normal crush mode of honeycomb is progressive plastic buckling. Low energy absorption (or abnormal) modes include transverse splitting and global buckling. To obtain a consistent normal mode of deformation under wide testing conditions, a confined compression test was developed. A series of confined compressions on T-, L-, and W-directions were performed to get crush parameters for the orthotropic crush model. The temperature dependence and loading rate effects on crush parameters were also obtained.

scholarly journals Real Gas Model Parameters for High-Density Combustion from Chemical Kinetic Model Data

ACS Omega ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 3074-3082
Author(s):  
Chenwei Zheng ◽  
Deshawn Murray Coombs ◽  
Benjamin Akih-Kumgeh
Keyword(s):  
Kinetic Model ◽  
Chemical Kinetic ◽  
High Density ◽  
Model Parameters ◽  
Model Data ◽  
Chemical Kinetic Model ◽  
Real Gas

scholarly journals Double plasma resonance instability as a source of solar zebra emission

2018 ◽  
Vol 611 ◽  
pp. A60 ◽  
Author(s):  
J. Benáček ◽  
M. Karlický
Keyword(s):  
Growth Rates ◽  
Solar Radio ◽  
Plasma Resonance ◽  
Hot Electrons ◽  
Model Parameters ◽  
Maximal Growth ◽  
Specific Mode ◽  
Hybrid Waves ◽  
Multi Mode ◽  
Good Agreement

Context. The double plasma resonance (DPR) instability plays a basic role in the generation of solar radio zebras. In the plasma, consisting of the loss-cone type distribution of hot electrons and much denser and colder background plasma, this instability generates the upper-hybrid waves, which are then transformed into the electromagnetic waves and observed as radio zebras. Aims. In the present paper we numerically study the double plasma resonance instability from the point of view of the zebra interpretation. Methods. We use a 3-dimensional electromagnetic particle-in-cell (3D PIC) relativistic model. We use this model in two versions: (a) a spatially extended “multi-mode” model and (b) a spatially limited “specific-mode” model. While the multi-mode model is used for detailed computations and verifications of the results obtained by the “specific-mode” model, the specific-mode model is used for computations in a broad range of model parameters, which considerably save computational time. For an analysis of the computational results, we developed software tools in Python. Results. First using the multi-mode model, we study details of the double plasma resonance instability. We show how the distribution function of hot electrons changes during this instability. Then we show that there is a very good agreement between results obtained by the multi-mode and specific-mode models, which is caused by a dominance of the wave with the maximal growth rate. Therefore, for computations in a broad range of model parameters, we use the specific-mode model. We compute the maximal growth rates of the double plasma resonance instability with a dependence on the ratio between the upper-hybrid ωUH and electron-cyclotron ωce frequency. We vary temperatures of both the hot and background plasma components and study their effects on the resulting growth rates. The results are compared with the analytical ones. We find a very good agreement between numerical and analytical growth rates. We also compute saturation energies of the upper-hybrid waves in a very broad range of parameters. We find that the saturation energies of the upper-hybrid waves show maxima and minima at almost the same values of ωUH∕ωce as the growth rates, but with a higher contrast between them than the growth rate maxima and minima. The contrast between saturation energy maxima and minima increases when the temperature of hot electrons increases. Furthermore, we find that the saturation energy of the upper-hybrid waves is proportional to the density of hot electrons. The maximum saturated energy can be up to one percent of the kinetic energy of hot electrons. Finally we find that the saturation energy maxima in the interval of ωUH∕ωce = 3–18 decrease according to the exponential function. All these findings can be used in the interpretation of solar radio zebras.

scholarly journals High-Density Polyethylene and Heat-Treated Bamboo Fiber Composites: Nonisothermal Crystallization Properties

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Yanjun Li ◽  
Lanxing Du ◽  
Zhen Zhang ◽  
Qinglin Wu
Keyword(s):  
High Density Polyethylene ◽  
Three Dimensional ◽  
Treatment Temperature ◽  
High Density ◽  
Model Parameters ◽  
Scanning Calorimetry ◽  
Kinetic Rate Constant ◽  
Nonisothermal Crystallization ◽  
Heat Treated ◽  
Bamboo Fibers

The effect of heat-treated bamboo fibers (BFs) on nonisothermal crystallization of high-density polyethylene (HDPE) was investigated using differential scanning calorimetry under nitrogen. The Avrami-Jeziorny model was used to fit the measured crystallization data of the HDPE/BF composites and to obtain the model parameters for the crystallization process. The heat flow curves of neat HDPE and HDPE/heat-treated BF composites showed similar trends. Their crystallization mostly occurred within a temperature range between 379 K and 399 K, where HDPE turned from the liquid phase into the crystalline phase. Values of the Avrami exponent (n) were in the range of 2.8~3.38. Lamellae of neat HDPE and their composites grew in a three-dimensional manner, which increased with increased heat-treatment temperature and could be attributed to the improved ability of heterogeneous nucleation and crystallization completeness. The values of the modified kinetic rate constant (KJ) first increased and then decreased with increased cooling rate because the supercooling was improved by the increased number of nucleating sites. Heat-treated BF and/or a coupling agent could act as a nucleator for the crystallization of HDPE.

Coupling of Nanocavitation With Cyclic Deformation Behavior of High-Density Polyethylene Below the Yield Point

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Kamel Hizoum ◽  
Yves Rémond ◽  
Stanislav Patlazhan
Keyword(s):  
Yield Point ◽  
High Density Polyethylene ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
High Density ◽  
Model Parameters ◽  
Mechanical Modeling ◽  
Lower Stress ◽  
Structure Sensitive ◽  
The Common

The peculiarities of viscoelastic behavior of high-density polyethylene (HDPE) subjected to the uniaxial cyclic tensions and retractions below the yield point are studied. This required using three different deformation programs including (i) the successive increase in strain maximum of each cycle, (ii) the controlled upper and lower stress boundaries, and (iii) the fixed strain at the backtracking points. The experimental data are analyzed in a framework of the modified structure-sensitive model (Oshmyan et al., 2006, “Principles of Structural–Mechanical Modeling of Polymers and Composites,” Polym. Sci. Ser. A, 48, pp. 1004–1013) of semicrystalline polymers. It is supposed that increase in the interlamellar nanovoid volume fraction results in speeding-up the plastic flow rate while decreasing cavitation rate. Consequently, a proper fitting of the stress–strain cyclic diagrams is obtained for the applied deformation programs within the common set of model parameters. This makes it possible to reveal evolution of nanovoid volume fraction in HDPE during cyclic deformations.

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