scholarly journals Numerical modeling of the porosity influence on the elastic properties of sintered materials

2019 ◽  
Vol 51 (2) ◽  
pp. 153-161
Author(s):  
Elmiladi Abdulrazag ◽  
Igor Balac ◽  
Katarina Colic ◽  
Aleksandar Grbovic ◽  
Milorad Milovancevic ◽  
...  
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Elastic Properties ◽  
Volume Fraction ◽  
Unit Cell ◽  
Material Microstructure ◽  
Two Phase ◽  
Material Porosity ◽  
Sintered Materials ◽  
Elastic Characteristics

The effect of structural porosity on the elastic properties of sintered materials was studied using the new multi-pore unit cell numerical model - MPUC. Comparison between proposed MPUC model and previously adopted two-phase unit cell - FCC numerical model as well as available experimental data in literature, was done by comparing obtained values for modulus of elasticity - E, shear modulus - G and Bulk modulus - K. Results obtained by proposed MPUC model are in excellent agreement with available experimental data in literature. It was confirmed that material porosity regarding pores? size (volume fraction) has noticeable influence on elastic properties of sintered material. Less porosity in the material microstructure generally leads to noticeable higher values of E, G and K. For fixed volume fraction, shape of pores has no significant influence on elastic characteristics.

scholarly journals Numerical modeling of the porosity influence on strength of structural materials

2019 ◽  
Vol 51 (4) ◽  
pp. 459-467
Author(s):  
Mohamed Higaeg ◽  
Igor Balac ◽  
Aleksandar Grbovic ◽  
Milorad Milovancevic ◽  
Milos Jelic
Keyword(s):  
Experimental Data ◽  
Structural Material ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Structural Materials ◽  
Material Strength ◽  
Material Microstructure ◽  
Dimensional Unit ◽  
Material Porosity ◽  
Porosity Volume Fraction

The effect of micro-scale structural low-level porosity on strength of structural materials was studied using the three-dimensional Unit Cell Numerical Model - UCNM. A comparison between proposed UCNM and available experimental data in literature was done by comparing obtained values for stress concentration factor - SCF for different sizes and shapes of pore. Results for normalized strength obtained by proposed UCNM model are in agreement with available experimental data published in literature. It was confirmed that material porosity in form of closed pores, regarding pores? size (volume fraction) and shape, has note cable influence on strength of structural material. Less porosity in the material microstructure generally leads to higher values of material strength. For fixed porosity volume fraction, shape of pores has an impact on strength of structural material.

Micromechanical analysis of effective mechanical properties of graphene/ZrO2-hybrid poly (methyl methacrylate) nanocomposites

2021 ◽  
pp. 251659842110388
Author(s):  
Ankit Rathi ◽  
S. I. Kundalwal
Keyword(s):  
Methyl Methacrylate ◽  
Elastic Properties ◽  
Mechanical Performance ◽  
Volume Fraction ◽  
Element Model ◽  
Two Phase ◽  
Effective Elastic Properties ◽  
Poly Methyl Methacrylate ◽  
Three Phase ◽  
Effective Mechanical Properties

In this study, the tensile properties of two-phase and three-phase graphene/ZrO2-hybrid poly (methyl methacrylate) (PMMA) nanocomposites are investigated by developing finite element model using ANSYS. Primarily, the effective elastic properties of two- and three-phase graphene/ZrO2-hybrid PMMA nanocomposites (GRPCs) are estimated by developing mechanics of material (MOM) model. Results indicated that the effective elastic properties of GRPCs increase with an increase in the volume fraction of graphene. Also, the stiffness of GRPCs is increased by 78.12% with increasing in the volume fraction of graphene from 0.1 to 0.5 Vf. The incorporation of an additional ZrO2 interphase significantly improved the mechanical performance of resulting GRPCs.

Effective Property Estimation of CMC Minicomposites Considering Porosity

2018 ◽  
Author(s):  
Abhilash M. Nagaraja ◽  
Suhasini Gururaja
Keyword(s):  
Elastic Properties ◽  
Volume Fraction ◽  
Matrix Material ◽  
Ceramic Matrix Composites ◽  
Unit Cell ◽  
Matrix Cracking ◽  
Failure Behavior ◽  
Numerical Homogenization ◽  
Element Analysis ◽  
Micro Scale

Ceramic matrix composites (CMCs) are a promising subclass of composite materials suitable for high temperature applications. CMCs exhibit multiple damage mechanisms such as matrix cracking, interphase debonding, fiber sliding, fiber pullout, delaminations etc. Additionally, process induced defects such as matrix porosity exists at multiple length scales and has a considerable influence on the mechanical and failure behavior of CMCs. In the current work, the effect of intra-tow porosity, which exist at the micro-scale, on the mechanical behavior of CMCs has been investigated by numerical homogenization. Micro-scale response of 3 phase CMCs with intra tow pores has been obtained by finite element analysis based homogenization. Pores have been modeled as non-intersecting ellipsoids in a square unit cell representative of matrix material. The effective mechanical properties of porous matrix at the micro scale has been obtained from numerical homogenization, which are in good agreement with Mori-Tanaka mean field theory. The obtained matrix elastic properties have then been included in a three phase unit cell consisting of fiber, interphase and matrix representative of CMC microstructure. The effect of porosity volume fraction and aspect ratio on the effective elastic properties of the composite have been reported. Homogenization approach to model statistical distribution of pore size obtained from X-ray computed tomography of CMC minicomposite has been proposed.

Influence of Jordanian zeolite on the performance of a solar still: experiments and CFD simulation studies

2016 ◽  
Vol 16 (6) ◽  
pp. 1700-1709 ◽  
Author(s):  
Yazan Taamneh
Keyword(s):  
Experimental Data ◽  
Phase Change ◽  
Cfd Simulation ◽  
Volume Fraction ◽  
Solar Still ◽  
Cfd Simulations ◽  
Two Phase ◽  
Vof Model ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Computational fluid dynamics (CFD) simulations were performed for experiments carried out with two identical pyramid-shaped solar stills. One was filled with Jordanian zeolite-seawater and the second was filled with seawater only. This work is focused on CFD analysis validation with experimental data conducted using a model of phase change interaction (evaporation-condensation model) inside the solar still. A volume-of-fluid (VOF) model was used to simulate the inter phase change through evaporation-condensation between zeolite-water and water vapor inside the two solar stills. The effect of the volume fraction of the zeolite particles (0 ≤ ϕ ≤ 0.05) on the heat and distillate yield inside the solar still was investigated. Based on the CFD simulation results, the hourly quantity of freshwater showed a good agreement with the corresponding experimental data. The present study has established the utility of using the VOF two phase flow model to provide a reasonable solution to the complicated inter phase mass transfer in a solar still.

scholarly journals Modelling of elastic properties of sintered porous materials

2013 ◽  
Vol 469 (2154) ◽  
pp. 20120689 ◽  
Author(s):  
A. V. Manoylov ◽  
F. M. Borodich ◽  
H. P. Evans
Keyword(s):  
Experimental Data ◽  
Porous Materials ◽  
Damage Accumulation ◽  
Statistical Distributions ◽  
Metal Powders ◽  
Combined Model ◽  
Loaded Material ◽  
Sintered Materials ◽  
Good Agreement ◽  
Elastic Characteristics

Models for prediction of the elastic characteristics of natural and synthetic porous materials are re-examined and new models are introduced. First, the Vavakin–Salganik (VS) model for materials with isolated spherical pores is extended in order to take into account various statistical distributions of pore sizes. It is shown that the predictions of the extended VS model are in good agreement with experimental data for porous materials with isolated pores such as foamed titanium, porous glass and sandstone. However, the model is in a considerable disagreement with the experimental data for materials sintered from metal powders. The disagreement is explained by the presence of merged and open pores whose shapes cannot be well approximated as spheres. Using the theory of geometrical probabilities, the amount of pores that are close enough to overlap is estimated, and a model is introduced where merging pores are modelled as corresponding ellipsoids. Another modification is proposed to take into account open pores. This modification is based on the classical Rabotnov–Kachanov approach to damage accumulation in the loaded material. Finally, predictions given by the above models, and their combination is compared with experiments. A good agreement is observed between the combined model and the available experimental data for a variety of sintered materials.

Comparison of Single and Two-Phase Models for the Study of Mixed Convection Flows With Nanofluids

2010 ◽  
Author(s):  
Mahmood Akbari ◽  
Amin Behzadmehr ◽  
Nicolas Galanis
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mixed Convection ◽  
Single Phase ◽  
Volume Fraction ◽  
Solid Particles ◽  
Two Phase ◽  
Prediction Ability ◽  
Numerical Predictions ◽  
Phase Models

The single phase and three different two phase models (Volume of fluid, Mixture and Eulerian) are used to analyse laminar mixed convection flow of Al2O3-water nanofluids in a horizontal tube, in order to evaluate their prediction ability. The flow is considered steady and developing. The fluid’s physical properties are temperature dependent whereas those of the solid particles are constant. A uniform heat flux is applied at the fluid-solid interface. Two different Reynolds numbers and three different volume fractions have been considered. The governing three-dimensional partial differential equations are elliptical in all directions and coupled. Predicted convective heat transfer coefficients, velocity, and temperature profiles, as well as secondary flow’s velocity vectors and temperature contours are compared at different axial positions. To validate the comparisons and verify the accuracy of the results, the numerical predictions are compared with corresponding experimental data. There are essentially no differences between the predictions of the two-phase models; however their results are significantly different from those of the single-phase approach. Two-phase model results are closer to the experimental data, but they show an unrealistic increase in heat transfer for small changes of the particle volume fraction. Hydrodynamically, the two-phase and single-phase approaches perform almost the same but their thermal predictions are quite different.

scholarly journals Dielectric, Electromechanical and Elastic Properties of K (NH ) H PO Compounds

2015 ◽  
Vol 16 (1) ◽  
pp. 116-122
Author(s):  
L. Korotkov ◽  
Likhovaja Likhovaja ◽  
R. Levitsky ◽  
I. Zachek ◽  
A. Vdovych
Keyword(s):  
Experimental Data ◽  
Elastic Properties ◽  
Microscopic Theory ◽  
Thermodynamic Theory ◽  
Elastic Characteristics

We describe the available experimental data for the dielectric, piezoelectric, and elastic characteristics of the  antiferroelectric crystals, using the proposed microscopic theory. Within the framework of the thermodynamic theory and using the obtained experimental data we calculate the dielectric, piezoelectrlic, and elastic characteristics of the  compounds at > 0.32.

Bubbly, Two-Phase Flow in the Anode Channel of a Passive, Tubular Direct Methanol Fuel Cell

2011 ◽  
Author(s):  
Hafez Bahrami ◽  
Amir Faghri
Keyword(s):  
Experimental Data ◽  
Direct Methanol Fuel Cell ◽  
Volume Fraction ◽  
Catalyst Layer ◽  
Two Phase ◽  
Direct Methanol ◽  
Cell Current ◽  
Gas Volume Fraction ◽  
Gas Volume ◽  
Methanol Fuel Cell

A numerical study is presented to investigate the turbulent, two-phase, steady state, isothermal, bubbly flow characteristic in the anode channel of a passive, tubular direct methanol fuel cell (DMFC) in order to accurately predict the gas volume fraction distribution along the channel. Accumulation of carbon dioxide gas bubbles at the channel’s wall hinders the diffusion of the fuel from the channel to the catalyst layer. The conservation governing equations of the mass and momentum for both the continuous (methanol and water solution) and dispersed (CO2 bubbles) phases in the bubbly regime are solved using the multi-fluid technique. Turbulence in the liquid phase is formulated by employing the classical, two-equation k–ε model. Due to the lack of experimental data regarding the gas volume fraction in the anode channel of DMFCs, the proposed model was initially applied to the bubble plum in a cylindrical liquid bath in which air is injected into the water from a nozzle located at the bottom-center of the bath. The results are compared with the existing experimental data in the literature for the gas volume fraction and the liquid velocity in the bath. Finally, the model is successfully extended to the anode channel of a tubular DMFC operating passively in the vertical orientation in which the CO2 gas bubbles are injected through the wall. The rate of gas injection depends on the cell current density which is assumed to be uniform along the anode catalyst layer and the channel’s wall. It is found that the gas volume fraction significantly changes along the channel from a large value at the bottom of the channel to a lower value at the top. The flow field inside the channel is also investigated for different cell current densities.

scholarly journals Effective thermal conductivity modeling with primary and secondary parameters for two-phase materials

2010 ◽  
Vol 14 (2) ◽  
pp. 393-407 ◽  
Author(s):  
Kumar Palaniswamy ◽  
Raja Venugopal ◽  
Karthikeyan Palaniswamy
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Unit Cell ◽  
Maximum Deviation ◽  
Algebraic Equations ◽  
Two Phase ◽  
Wide Range ◽  
Maximum Conductivity ◽  
Spatially Periodic

In this article, the collocated parameter models are used to estimate the effective thermal conductivity of the two-phase materials including the effect of various inclusions in the unit cell. The algebraic equations are derived using unit cell based isotherm approach for two dimensional spatially periodic medium. The geometry of the medium is considered as a matrix of touching and non-touching in-line octagon and hexagon cylinders. The models are used to predict the thermal conductivity of numerous two-phase materials (maximum conductivity ratio of 1000 and concentration ranging between 0 and 1). The estimated thermal conductivity data is in good agreement with the experimental data within ?15.84%, ?18.14% maximum deviation, respectively, from octagon and hexagon cylinders for various two-phase systems. The obtained results are compared with a wide range of experimental data for various geometrical configurations to estimate the effective thermal conductivity of two-phase materials.

The Linear Elastic Properties of Open-Cell Foams

1988 ◽  
Vol 55 (2) ◽  
pp. 341-346 ◽  
Author(s):  
W. E. Warren ◽  
A. M. Kraynik
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
Cross Section ◽  
Elastic Constants ◽  
Volume Fraction ◽  
Cellular Materials ◽  
Unit Cell ◽  
Open Cell ◽  
Linear Elastic ◽  
Open Cell Foams

A theoretical model for the linear elastic properties of three-dimensional open-cell foams is developed. We consider a tetrahedral unit cell, which contains four identical half-struts that join at equal angles, to represent the essential microstructural features of a foam. The effective continuum stress is obtained for an individual tetrahedral element arbitrarily oriented with respect to the principal directions of strain. The effective elastic constants for a foam are determined under the assumption that all possible orientations of the unit cell are equally probable in a representative volume element. The elastic constants are expressed as functions of compliances for bending and stretching of a strut, whose cross section is permitted to vary with distance from the joint, so the effect of strut morphology on effective elastic properties can be determined. Strut bending is the primary distortional mechanism for low-density foams with tetrahedral microstructure. For uniform strut cross section, the effective Young’s modulus is proportional to the volume fraction of solid material squared, and the coefficient of proportionality depends upon the specific strut shape. A similar analysis for cellular materials with cubic microstructure indicates that strut extension is the dominant distortional mechanism and that the effective Young’s modulus is linear in volume fraction. Our results emphasize the essential role of microstructure in determining the linear elastic properties of cellular materials and provide a theoretical framework for investigating nonlinear behavior.

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