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1
Content available remote

Predicting the Poisson Ratio of Lightweight Concretes using Artificial Neural Network

100%
Davraz M., Kilinçarslan Ş., Ceylan H.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 2B
B-184-B-186
EN
Artificial neural network is generally information processing system and a computer program that imitates human brain neural network system. By entering the information from outside, artificial neural network can be trained on examples related to a problem, so that modeling of the problem is provided. In this study, compressive strength, Poisson ratio of the lightweight concrete specimens, which have different natural lightweight aggregates, were modeled with artificial neural network. The data which were provided by artificial neural network model were compared with the data obtained from experimental study and a good agreement was determined between the results.
2
Content available remote

Mechanical Performances of Artificial Aggregated Lightweight Concrete

100%
Davraz M., Ceylan H., Kılınçarslan Ş.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 4
1246-1250
EN
In this study, some physical and mechanical performances of artificial aggregated lightweight concretes were compared. Special empirical models were developed to estimate the elasticity modulus of lightweight aggregate concrete (LWAC). Five different natural aggregates and one artificial lightweight aggregate material were used throughout the research. Mixture proportions were kept as constant values in all concrete mixtures. All mixtures were cast into cubic, prismatic and cylindrical concrete standard moulds and they were cured at the same curing conditions. A series of physical and mechanical properties, such as density, compressive strength and elasticity modulus for LWAC were experimentally determined. According to the research findings a few empirical models were statistically developed for estimating the elasticity modulus and Poisson's ratio of LWAC and a new diagram practically to be used for estimating the Poisson's ratio of LWAC was also proposed.
3
Content available remote

Stress Induced Phononic Properties and Surface Waves in 2D Model of Auxetic Crystal

51%
Trzupek D., Twaróg D., Zieliński P.
Acta Physica Polonica A
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2009
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vol. 115
|
issue 2
576-578
EN
Elastic stiffness parameters are determined in a 2D model system of rigid rods interacting by harmonic force constants. Any positive ("normal" crystal) or negative (auxetic crystal) Poisson ratio can be obtained in this model as a function of the external stress. Conditions for opening an absolute stop band (phononic crystal) and for various kinds of surface waves are obtained.
4
Content available remote

First Principles Study of Mechanical Stability and Thermodynamic Properties of K₂S under Pressure and Temperature Effect

51%
Boufadi F., Bidai K., Ameri M., Bentouaf A., Bensaid D., Azzaz Y., Ameri I.
Acta Physica Polonica A
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2016
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vol. 129
|
issue 3
315-322
EN
First principles calculations on structural, elastic and thermodynamic properties of K₂S have been made using the full-potential augmented plane-waves plus local orbitals within density functional theory using generalized gradient approximation for exchange correlation potentials. The ground state lattice parameter, bulk moduli have been obtained. The second-order elastic constants, Young and shear modulus, Poisson ratio, have also been calculated. Calculated structural, elastic and other parameters are in good agreement with available data. The elastic constants and thermodynamic quantities under high pressure and temperature are also calculated and discussed.
5
Content available remote

Surface Dynamics and Phononic Properties of 2D Field Tunable Auxetic Crystal

51%
Twaróg D., Trzupek D., Zieliński P.
Acta Physica Polonica A
|
2009
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vol. 115
|
issue 2
579-582
EN
The lattice in-plane dynamics is studied as a function of external field in a model of auxetic crystal consisting of rigid polar rods and of elastic springs. The phase speed of the transverse acoustic wave propagating parallel to the polar rods is shown to be higher than the speed of the longitudinal wave at strong fields. An absolute stop band for the lattice waves opens in the whole Brillouin zone with increasing field. The surface waves and resonances at a surface parallel to the rods are studied. Infinitely narrow resonances called exceptional surface waves are found within bulk bands at certain specific values of the parameters characterizing the surface. Generally, the surface layer should be significantly heavier and stiffer than the substrate for the phenomenon to occur.
6
Content available remote

Mechanical Properties of Tetragonal and Orthorhombic Phases of Quasi-One-Dimensional Antiferromagnet KCuF_{3}

45%
Legut D., Wdowik U.
|
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vol. 126
|
issue 1
14-15
EN
The density functional theory was used to calculate the elastic constants for the two tetragonal (a-type) and (d-type), and the orthorhombic structures of KCuF_{3}. Based on the single elastic constants the polycrystalline mechanical properties such as bulk, shear, Young moduli and Poisson ratio using Reuss-Voigt-Hill averaging method were estimated. Furthermore, the sound transverse and longitudional velocities (along the a-axis and c-axis) were calculated and the Debye temperatures were determined for all three investigated phases.
7
Content available remote

Micromechanical Investigation of Elastic Properties for Polypropylene Fiber-Matrix Composite

45%
Günay E.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 1
143-146
EN
In this study, the mechanical properties of unidirectional fiber composites were determined by using the representative volume element method. The aim of this study was to determine the equivalent elastic constants for the "fiber composite polymer (PPE/PP) thermoplastic material" used in a wide variety of engineering applications. At the first step, the micromechanical model was applied to the polypropylene (PP) fiber-matrix composite, and then the microstructure form of the material was analyzed by finite element method considering "rule of mixture". The symmetry boundary conditions have been applied by using the representative volume elements in 3D finite element models. The SOLID187 mesh element of ANSYS was used for the presentation of the microstructure form of the fiber-matrix composite. The elastic constants obtained in this study were respectively as follows: the longitudinal elastic modulus and the Poisson ratio E₁, ν₁₂, the transverse elastic modulus and the Poisson ratio E₂, ν₂₃. For verification, the numerical results were also compared with the literature.
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