scholarly journals On the Effect of Unit-Cell Parameters in Predicting the Elastic Response of Wood-Plastic Composites

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Fatemeh Alavi ◽  
Amir Hossein Behravesh ◽  
Abbas S. Milani ◽  
Davoud Karimi
Keyword(s):  
Finite Element ◽  
Modulus Of Elasticity ◽  
Strain Curve ◽  
Unit Cell ◽  
Elastic Response ◽  
Geometrical Parameters ◽  
Uniaxial Test ◽  
Cell Parameters ◽  
Plastic Composite ◽  
The Difference

This paper presents a study on the effect of unit-cell geometrical parameters in predicting elastic properties of a typical wood plastic composite (WPC). The ultimate goal was obtaining the optimal values of representative volume element (RVE) parameters to accurately predict the mechanical behavior of the WPC. For each unit cell, defined by a given combination of the above geometrical parameters, finite element simulation in ABAQUS was carried out, and the corresponding stress-strain curve was obtained. A uniaxial test according to ASTM D638-02a type V was performed on the composite specimen. Modulus of elasticity was determined using hyperbolic tangent function, and the results were compared to the sets of finite element analyses. Main effects of RVE parameters and their interactions were demonstrated and discussed, specially regarding the inclusion of two adjacent wood particles within one unit cell of the material. Regression analysis was performed to mathematically model the RVE parameter effects and their interactions over the modulus of elasticity response. The model was finally employed in an optimization analysis to arrive at an optimal set of RVE parameters that minimizes the difference between the predicted and experimental moduli of elasticity.

Kinematical and Dynamical CBED Pattern Models: Increasing the Accuracy of the Unit-Cell Parameter Measurements Based on CBED Patterns

1990 ◽  
Vol 48 (2) ◽  
pp. 540-541
Author(s):  
I.N. Yadhikov ◽  
S.K. Maksimov
Keyword(s):  
Reciprocal Lattice ◽  
Unit Cell ◽  
Reciprocal Lattice Vector ◽  
Unit Cell Parameters ◽  
Lattice Vector ◽  
Cell Parameters ◽  
Accuracy Of Measurements ◽  
The Difference ◽  
Image Position ◽  
Convergent Beam

Convergent beam electron diffraction (CBED) is widely used as a microanalysis tool. By the relative position of HOLZ-lines (Higher Order Laue Zone) in CBED-patterns one can determine the unit cell parameters with a high accuracy up to 0.1%. For this purpose, maps of HOLZ-lines are simulated with the help of a computer so that the best matching of maps with experimental CBED-pattern should be reached. In maps, HOLZ-lines are approximated, as a rule, by straight lines. The actual HOLZ-lines, however, are different from the straights. If we decrease accelerating voltage, the difference is increased and, thus, the accuracy of the unit cell parameters determination by the method becomes lower.To improve the accuracy of measurements it is necessary to give up the HOLZ-lines substitution by the straights. According to the kinematical theory a HOLZ-line is merely a fragment of ellipse arc described by the parametric equationwith arc corresponding to change of β parameter from -90° to +90°, wherevector, h - the distance between Laue zones, g - the value of the reciprocal lattice vector, g‖ - the value of the reciprocal lattice vector projection on zero Laue zone.

scholarly journals Structural Transformations in Crystals Induced by Radiation and Pressure. Part 7. Molecular and Crystal Geometries as Factors Deciding about Photochemical Reactivity under Ambient and High Pressures

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 299 ◽  
Author(s):  
Krzysztof Konieczny ◽  
Arkadiusz Ciesielski ◽  
Julia Bąkowicz ◽  
Tomasz Galica ◽  
Ilona Turowska-Tyrk
Keyword(s):  
High Pressures ◽  
Unit Cell ◽  
Geometrical Parameters ◽  
Isopropyl Group ◽  
Unit Cell Parameters ◽  
Photochemical Reactivity ◽  
Space Group ◽  
Cell Parameters ◽  
Pressure Part ◽  
Asymmetric Unit Cell

We studied the photochemical reactivity of salts of 4-(2,4,6-triisopropylbenzoyl)benzoic acid with propane-1,2-diamine (1), methanamine (2), cyclohexanamine (3), and morpholine (4), for compounds (1), (3), and (4) at 0.1 MPa and for compounds (1) and (2) at 1.3 GPa and 1.0 GPa, respectively. The changes in the values of the unit cell parameters after UV irradiation and the values of the intramolecular geometrical parameters indicated the possibility of the occurrence of the Norrish–Yang reaction in the case of all the compounds. The analysis of the intramolecular geometry and free spaces revealed which o-isopropyl group takes part in the reaction. For (1), the same o-isopropyl group should be reactive at ambient and high pressures. In the case of (2), high pressure caused the phase transition from the space group I2/a with one molecule in the asymmetric unit cell to the space group P1¯ with two asymmetric molecules. The analysis of voids indicated that the Norrish–Yang reaction is less probable for one of the two molecules. For the other molecule, the intramolecular geometrical parameters showed that except for the Norrish–Yang reaction, the concurrent reaction leading to the formation of a five-membered ring can also proceed. In (3), both o-isopropyl groups are able to react; however, the bigger volume of a void near 2-isopropyl may be the factor determining the reactivity. For (4), only one o-isopropyl should be reactive.

Packing analysis of carbohydrates and polysaccharides. 16. The crystal structures of celluloses IVI and IVII

1985 ◽  
Vol 63 (1) ◽  
pp. 173-180 ◽  
Author(s):  
Eric S. Gardiner ◽  
Anatole Sarko
Keyword(s):  
Crystal Structures ◽  
Unit Cell ◽  
Hydroxyl Groups ◽  
Data Sets ◽  
Cell Parameters ◽  
The Difference ◽  
Cellulose Iv ◽  
Chain Conformations ◽  
Probable Space ◽  
Packing Analysis

The crystal structures of cellulose polymorphs IVI and IVII have been determined by X-ray fiber diffraction analysis combined with stereochemical model refinement. Both structures crystallize in a two-chain unit cell of essentially identical parameters. The most probable space group in both cases is P1. The chain conformations, although close to two-fold helical, are marked by unequal rotational positions of the O(6) hydroxyl groups in adjacent residues. Despite identical unit cell parameters, the structures differ in chain polarity: in cellulose IVI both chains of the unit cell are parallel, whereas in cellulose IVII they are antiparallel. The difference in polarity is further substantiated by the results of chemical conversions which show that cellulose IVI is converted to cellulose I, and cellulose IVII is converted to cellulose II, via parallel and antiparallel cellulose triacetates, respectively. The reliability of the structure analyses is indicated by the residual R″ = 0.115 for cellulose IVI and 0.094 for cellulose IVII, for data sets of 41 and 43 reflections, respectively.

scholarly journals Finite Element Study on the Effect of Geometrical Parameters on the Mechanical Behavior of 3D Reentrant Auxetic Honeycombs.

2022 ◽  
pp. 1-7
Author(s):  
Sai Adithya Vanga ◽  
Aravind Rajan Ayagara ◽  
Rohan Gooty ◽  
Taha Hussain ◽  
Moulshree Srivastava
Keyword(s):  
Finite Element ◽  
Energy Absorption ◽  
Poisson’S Ratio ◽  
Bulk Material ◽  
Three Dimensional ◽  
Unit Cell ◽  
Poisson's Ratio ◽  
Geometrical Parameters ◽  
Self Healing ◽  
Strain Behavior

Auxetic materials are a special case of cellular materials, which exhibit a negative Poisson’s ratio. This in fact is the reason behind their peculiar behavior i.e. lateral shrinkage under longitudinal compression and vice versa. Since these materials do not obey the laws of “normal” materials and go beyond common sense, they are still an emerging class which can be put to use for various purposes like self-locking reinforcing fibers in composites, controlled release media, self-healing films, piezoelectric sensors, and also be used in biomedical engineering. Their stress-strain behavior, Poisson’s ratio and impact energy absorption are controlled by bulk material as well as the unit cell geometry. Among many forms of auxetic structures available, we have chosen a three-dimensional reentrant auxetic honeycomb unit cell. The unit cell geometrical parameters were taken from literature. In this study, we try to understand the effects of strut angle through finite element simulations while keeping the bulk material, unit cell size, strut thickness and number of repetitions constant. A total of three different angles were tested, based on which we conclude that as angle increases, the Poisson’s ratio increases and Energy absorption is maximum at 30 deg.

STUDY ON THE FRACTURE BEHAVIOR OF W-NI-FE HEAVY ALLOYS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5453-5458 ◽  
Author(s):  
WEIDONG SONG ◽  
JIANGUO NING ◽  
HAIYAN LIU
Keyword(s):  
Finite Element ◽  
Cell Model ◽  
Strain Curve ◽  
Tensile Tests ◽  
Unit Cell ◽  
Tungsten Particle ◽  
Tungsten Alloys ◽  
Numerical Predictions ◽  
Fracture Patterns ◽  
Fracture Behaviors

The fracture behaviors of tungsten alloys 91 W -6.3 Ni -2.7 Fe were investigated by tensile tests and numerical simulations. Firstly, tensile tests were conducted on the S-570 SEM with an in-situ tensile stage. With this system, the process of deformation, damage and evolution in micro-area can be tracked and recorded, and at the same time, the load-strain curve can be drawn. Secondly, the 2D finite element model of a unit cell for the tungsten alloys was established by using finite element program. By copying the unit cell model, the macro-model of the alloys was given. Dozen of cases were performed to simulate the fracture behaviors of tungsten alloys. Thirdly, the random model of the alloys was established. The fracture patterns of the alloys were investigated by the model. The interface between the tungsten particle and the matrix was explored in details. The effect of interface strength on the fracture patterns of the alloys was taken into account. A good agreement was achieved between the experimental results and the numerical predictions.

scholarly journals Heat capacity and thermal expansion of yttrium tantalate

2019 ◽  
Vol 484 (2) ◽  
pp. 181-183
Author(s):  
A. V. Khoroshilov ◽  
A. A. Ashmarin ◽  
V. N. Guskov ◽  
E. G. Sazonov ◽  
K. S. Gavrichev ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Thermal Expansion ◽  
Heat Capacities ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Scanning Calorimetry ◽  
Crystal Lattices ◽  
Cell Parameters ◽  
The Difference

The isobaric heat capacities of two monoclinic (M' and M) modifications of yttrium orthotantalate at temperatures 5–1300 K have been measured by the adiabatic and differential scanning calorimetry methods. It has been demonstrated that the difference in structure between the crystal lattices of M' and M has small effect in the heat capacity, and the difference between the heat capacities of these phases Cp(M)-Cp(M') is small, always positive, and increases in the range of the lowest temperatures. The unit cell parameters of M-YTaO4 have been determined as a function of temperature in the range 300–1173 K.

scholarly journals The microstructure of the rapidly solidified foil of the hypoeutectic alloy Sn – 4.4 wt. % Zn

2021 ◽  
pp. 44-52
Author(s):  
Vasili G. Shepelevich ◽  
Denis A. Zernitsa
Keyword(s):  
Diffusion Processes ◽  
Unit Cell ◽  
Hypoeutectic Alloy ◽  
Surface Layers ◽  
Two Phase ◽  
Unequal Distribution ◽  
Cell Parameters ◽  
Zinc Doping ◽  
The Difference ◽  
Rapidly Solidified

The article presents the results of a study of the microstructure of the rapidly solidified foil of the hypoeutectic alloy Sn – 4.4 wt. % Zn. It was found that the investigated alloy has a two-phase structure, which consists of solid solutions of tin and zinc. Doping of tin with zinc leads to a decrease in the unit cell parameter. The difference between the unit cell parameters of a rapidly solidified alloy in comparison with an alloy of pure tin tends to decrease during holding, which is due to strong supercooling of the melt during its production at ultrahigh speeds, and the formation of a supersaturated solid solution of zinc in tin, which, due to high homological temperatures, as a consequence, active diffusion processes, decomposes at room temperature. It has been established that a microcrystalline structure is formed in the foil of the alloy under study, in the cross section of which there are uniformly distributed equiaxed dispersed dark zinc precipitates against the background of a light tin matrix; the absence of zinc plates in the foil reduces the ability to brittle fracture. The unequal distribution of the average chord of random secants on the grains in the surface layers A is caused by the release of heat, which leads to a decrease in the supercooling of the subsequent layers of the melt, and an increase in the grain size as the crystallisation front moves. It was found that in the (301) plane along the [103] direction, tin twinning is observed, which occurs under the action of quenching stresses at high crystallisation rates. The alloy under study has a (100) tin texture, the formation of which is associated with the fact that the (100) plane is the most densely packed, which promotes the growth of grains with this orientation at the highest rate.

Monitoring photo-induced transformations in crystals of 2,6-difluorocinnamic acid under ambient conditions

2016 ◽  
Vol 72 (7) ◽  
pp. 593-599 ◽  
Author(s):  
Tomasz Galica ◽  
Julia Bąkowicz ◽  
Piotr Broda ◽  
Ilona Turowska-Tyrk
Keyword(s):  
Dicarboxylic Acid ◽  
Photochemical Reaction ◽  
Uv Light ◽  
Unit Cell ◽  
Initial Increase ◽  
Geometrical Parameters ◽  
Ambient Conditions ◽  
Unit Cell Parameters ◽  
Cell Parameters

Several conditions need to be fulfilled for a photochemical reaction to proceed in crystals. Some of these conditions, for example, geometrical conditions, depend on the particular type of photochemical reaction, but the rest are common for all reactions. The mutual directionality of two neighbouring molecules determines the kind of product obtained. The influence of temperature on the probability of a photochemical reaction occurring varies for different types of photochemical reaction and different compounds. High pressure imposed on crystals also has a big influence on the free space and the reaction cavity. The wavelength of the applied UV light is another factor which can initiate a reaction and sometimes determine the structure of a product. It is possible, to a certain degree, to control the packing of molecules in stacks by using fluoro substituents on benzene rings. The crystal and molecular structure of 2,6-difluorocinnamic acid [systematic name: 3-(2,6-difluorophenyl)prop-2-enoic acid], C9H6F2O2, (I), was determined and analysed in terms of a photochemical [2 + 2] dimerization. The molecules are arranged in stacks along theaaxis and the values of the intermolecular geometrical parameters indicate that they may undergo this photochemical reaction. The reaction was carried outin situand the changes of the unit-cell parameters during crystal irradiation by a UV beam were monitored. The values of the unit-cell parameters change in a different manner,viz.cell lengthaafter an initial increase starts to decrease,bafter a decrease starts to increase,cincreases and the unit-cell volumeVafter a certain increase starts to decrease. The structure of a partially reacted crystal,i.e.containing both the reactant and the product, namely 2,6-difluorocinnamic acid–3,4-bis(2,6-difluorophenyl)cyclobutane-1,2-dicarboxylic acid (0.858/0.071), 0.858C9H6F2O2·0.071C18H12F4O4, obtainedin situ, is also presented. The powder of compound (I) was irradiated with UV light and afterwards crystallized [as 3,4-bis(2,6-difluorophenyl)cyclobutane-1,2-dicarboxylic acid toluene hemisolvate, C18H12F4O4·0.5C7H8] in a space group different from that of the crystal containing thein-situdimer.

X-ray powder diffraction analysis of a new magnesium chromate hydrate, MgCrO4·11H2O

2012 ◽  
Vol 27 (1) ◽  
pp. 8-11 ◽  
Author(s):  
A. Dominic Fortes ◽  
Ian G. Wood
Keyword(s):  
Hydrogen Bond ◽  
Diffraction Analysis ◽  
Powder Diffraction ◽  
Unit Cell ◽  
Hydrogen Bond Network ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Bond Network ◽  
The Difference

A new hydrate of magnesium chromate is synthesized by quenching aqueous solutions of MgCrO4 in liquid nitrogen. MgCrO4·11H2O is isostructural with the rare mineral meridianiite (MgSO4·11H2O) being triclinic, $P{\bar 1}$, Z = 2, with unit-cell parameters a = 6.811 33(8) Å, b = 6.958 39(9) Å, c = 17.3850(2) Å, α = 87.920(1)°, β = 89.480(1)°, γ = 62.772(1)°, and V = 732.17(1) Å3 at −15 °C. The difference in unit-cell parameters between SO4- and CrO4-bearing species is only partially accounted for by the difference in S–O and Cr–O bond lengths; the remainder of the difference (over 90% in the cell volume) is attributed to weakening of the interpolyhedral hydrogen-bond network.

Sectioned rubisco crystals in TEM

1990 ◽  
Vol 48 (3) ◽  
pp. 664-665
Author(s):  
Gunnel Karlsson ◽  
Jan-Olov Bovin ◽  
Michael Bosma
Keyword(s):  
Plant Cell ◽  
Carbon Fixation ◽  
Unit Cell ◽  
Protein Crystals ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon

RuBisCO (D-ribulose-l,5-biphosphate carboxylase/oxygenase) is the most aboundant enzyme in the plant cell and it catalyses the key carboxylation reaction of photosynthetic carbon fixation, but also the competing oxygenase reaction of photorespiation. In vitro crystallized RuBisCO has been studied earlier but this investigation concerns in vivo existance of RuBisCO crystals in anthers and leaves ofsugarbeets. For the identification of in vivo protein crystals it is important to be able to determinethe unit cell of cytochemically identified crystals in the same image. In order to obtain the best combination of optimal contrast and resolution we have studied different staining and electron accelerating voltages. It is known that embedding and sectioning can cause deformation and obscure the unit cell parameters.

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