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Article
Publication date: 1 March 2006

Shutian Liu and Yongcun Zhang

In this paper, a homogenization‐based multi‐scale method for predicting the effective thermal conductivity of porous materials with radiation is presented, which considers…

Abstract

In this paper, a homogenization‐based multi‐scale method for predicting the effective thermal conductivity of porous materials with radiation is presented, which considers the effect of geometry and distribution of pores. Using homogenization method to solve the pure conductive problem of porous materials with periodic structure, the effective thermal conductivity without considering radiation is predicted, and a temperature field in a local domain of a unit cell is obtained. This temperature field is taken as the good approximation of the real temperature distribution, and the radiative thermal conductivity is obtained. The effect of the microstructure, the distribution and geometry of pores on heat transfer of porous materials is discussed. It is concluded that the dimension of the pores is an important influence factor on the thermal transfer property of porous materials if radiation is considered. Increasing the pore’s dimension enhances the contribution of radiation to the heat transfer property of porous materials. For porous materials with cylindrical and spherical pores, the radiative thermal conductivity is proportional to pore’s diameter.

Details

Multidiscipline Modeling in Materials and Structures, vol. 2 no. 3
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 17 August 2021

Mingkang Zhang, Yongqiang Yang, Meizhen Xu, Jie Chen and Di Wang

The purpose of this study is focused on the mechanical properties of multi-materials porous structures manufactured by selective laser melting (SLM).

Abstract

Purpose

The purpose of this study is focused on the mechanical properties of multi-materials porous structures manufactured by selective laser melting (SLM).

Design/methodology/approach

The Diamond structure was designed by the triply periodic minimal surface function in MATLAB, and multi-materials porous structures were manufactured by SLM. Compression tests were applied to analyze the anisotropy of mechanical properties of multi-materials porous structures.

Findings

Compression results show that the multi-materials porous structure has a strong anisotropy behavior. When the compression force direction is parallel to the material arrangement, multi-materials porous structure was compressed in a layer-by-layer way, which is the traditional deformation of the gradient structure. However, when the compression force direction is perpendicular to the material arrangement, the compression curves show a near-periodic saw-tooth waveform characteristic, and this kind of structure was compressed consistently. It is demonstrated that the combination with high strength brittle material and low strength plastic material improves compression mode, and plastic material plays a role in buffering fracture.

Originality/value

This research provides a new method for the design and manufacturing of multi-materials porous structures and an approach to change the compression behavior of the porous structure.

Details

Rapid Prototyping Journal, vol. 27 no. 9
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 12 May 2021

P.S. Liu and X.M. Ma

The purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different…

Abstract

Purpose

The purpose of this paper is to provide a summarization and review of the present author's main investigations on failure modes of reticular metal foams under different loadings in engineering applications.

Design/methodology/approach

With the octahedral structure model proposed by the present authors themselves, the fundamentally mechanical relations have been systematically studied for reticular metal foams with open cells in their previous works. On this basis, such model theory is continually used to investigate the failure mode of this kind of porous materials under compression, bending, torsion and shearing, which are common loading forms in engineering applications.

Findings

The pore-strut of metal foams under different compressive loadings will fail in the tensile breaking mode when it is brittle. While it is ductile, it will tend to the shearing failure mode when the shearing strength is half or nearly half of the tensile strength for the corresponding dense material and to the tensile breaking mode when the shearing strength is higher than half of the tensile strength to a certain value. The failure modes of such porous materials under bending, torsional and shearing loads are also similarly related to their material species.

Originality/value

This paper presents a distinctive method to conveniently analyze and estimate the failure mode of metal foams under different loadings in engineering applications.

Details

Multidiscipline Modeling in Materials and Structures, vol. 17 no. 4
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 6 August 2018

Yi Liu, Hao Wang, Yongfeng Liu, Meng Shi and Duolong Di

The purpose of this paper is to focus on the selection of the optimum porous material modified with poly-dopamine coating for peptides enrichment. The adsorption behaviors…

Abstract

Purpose

The purpose of this paper is to focus on the selection of the optimum porous material modified with poly-dopamine coating for peptides enrichment. The adsorption behaviors for peptides and the antioxidant capacity of peptides fraction purified by the porous materials were investigated.

Design/methodology/approach

The optimum porous material with the highest adsorption capacity for peptides was selected for surface modification. The surface modified porous material was characterized by SEM, nitrogen adsorption-desorption isotherm and color change.

Findings

The results showed that the porous material was successfully modified with poly-dopamine coating. Adsorption capacity for peptides of the modified porous material was enhanced compared to the original porous material. Antioxidant capacity of peptides fraction enriched by the modified porous material was much higher than that enriched by the original porous material, indicating that the introduction of poly-dopamine coating was inclined to enrich peptides with certain amino acid residues.

Research limitations/implications

The structures of peptides are a bit not clear, which is the subject of future investigation.

Practical implications

This contribution provides a method to design and prepare porous materials with poly-dopamine coating to separate and enrich peptides or peptides fraction with high antioxidant capacity.

Originality/value

It showed that polarity, surface area, pore diameter and interactions were contributed to high adsorption capacity. The peptides fraction purified by the modified porous material showed excellent antioxidant capacity through results of reduction of DPPH radical, because of the enrichment of the peptides with certain amino acids residues which were considered to enhance radical scavenging capacity. This paper provides new insights into designing and preparing porous materials with poly-dopamine coating to enrich peptides fraction with high antioxidant capacity.

Details

Pigment & Resin Technology, vol. 47 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

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Article
Publication date: 24 October 2018

Samuel Evans, Eric Jones, Peter Fox and Chris Sutcliffe

This paper aims to introduce a novel method for the analysis of open cell porous components fabricated by laser-based powder bed metal additive manufacturing (AM) for the…

Abstract

Purpose

This paper aims to introduce a novel method for the analysis of open cell porous components fabricated by laser-based powder bed metal additive manufacturing (AM) for the purpose of quality control. This method uses photogrammetric analysis, the extraction of geometric information from an image through the use of algorithms. By applying this technique to porous AM components, a rapid, low-cost inspection of geometric properties such as material thickness and pore size is achieved. Such measurements take on greater importance, as the production of porous additive manufactured orthopaedic devices increases in number, causing other, slower and more expensive methods of analysis to become impractical.

Design/methodology/approach

Here the development of the photogrammetric method is discussed and compared to standard techniques including scanning electron microscopy, micro computed tomography scanning and the recently developed focus variation (FV) imaging. The system is also validated against test graticules and simple wire geometries of known size, prior to the more complex orthopaedic structures.

Findings

The photogrammetric method shows an ability to analyse the variability in build fidelity of AM porous structures for use in inspection purposes to compare component properties. While measured values for material thickness and pore size differed from those of other techniques, the new photogrammetric technique demonstrated a low deviation when repeating measurements, and was able to analyse components at a much faster rate and lower cost than the competing systems, with less requirement for specific expertise or training.

Originality/value

The advantages demonstrated by the image-based technique described indicate the system to be suitable for implementation as a means of in-line process control for quality and inspection applications, particularly for high-volume production where existing methods would be impractical.

Details

Rapid Prototyping Journal, vol. 24 no. 8
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 5 February 2018

Gino Cortellessa, Fausto Arpino, Simona Di Fraia and Mauro Scungio

In this work, a new two-phase version of the finite element-based Artificial Compressibility (AC) Characteristic-Based Split (CBS) algorithm is developed and applied for…

Abstract

Purpose

In this work, a new two-phase version of the finite element-based Artificial Compressibility (AC) Characteristic-Based Split (CBS) algorithm is developed and applied for the first time to heat and mass transfer phenomena in porous media with associated phase change. The purpose of this study is to provide an alternative for the theoretical analysis and numerical simulation of multiphase transport phenomena in porous media. Traditionally, the more complex Separate Flow Model was used in which the vapour and liquid phases were considered as distinct fluids and mathematically described by the conservation laws for each phase separately, resulting in a large number of governing equations.

Design/methodology/approach

Even though the adopted mathematical model presents analogies with the conventional multicomponent mixture flow model, it is characterized by a considerable reduction in the number of the differential equations for the primary variables. The fixed-grid numerical formulation can be applied to the resolution of general problems that may simultaneously include a superheated vapour region, a two-phase zone and a sub-cooled liquid region in a single physical domain with irregular and moving phase interfaces in between. The local thermal non-equilibrium model is introduced to consider the heat exchange between fluid and solid within the porous matrix.

Findings

The numerical model is verified considering the transport phenomena in a homogenous and isotropic porous medium in which water is injected from one side and heated from the other side, where it leaves the computational domain in a superheated vapour state. Dominant forces are represented by capillary interactions and two-phase heat conduction. The obtained results have been compared with the numerical data available in the scientific literature.

Social implications

The present algorithm provides a powerful routine tool for the numerical modelling of complex two-phase transport processes in porous media.

Originality/value

For the first time, the stabilized AC-CBS scheme is applied to the resolution of compressible viscous flow transport in porous materials with associated phase change. A properly stabilized matrix inversion-free procedure employs an adaptive local time step that allows acceleration of the solution process even in the presence of large source terms and low diffusion coefficients values (near the phase change point).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 March 1995

D.R.J. Owen, S.Y. Zhao and J.G. Loughran

A finite element solution to the rolling of two‐phase materials ispresented and applied to the rolling of prepared sugar cane. The generalizedBiot theory is extended and…

Abstract

A finite element solution to the rolling of two‐phase materials is presented and applied to the rolling of prepared sugar cane. The generalized Biot theory is extended and modified to suit the present problem and the velocity of the solid skeleton and the pore pressure are taken as the primary unknowns. The finite element approach is applied to the governing equations for spatial discretization, followed by time domain discretization by standard difference methods. A constitutive relation evaluated from a finite element simulation of experiments performed on a constrained compression test cell is employed. The computational model of the rolling of prepared cane with two rolls is presented. The material parameters of prepared cane are described and their variation during the rolling process are derived and discussed. Numerical results are presented to illustrate the performance and capability of the model and solution procedures.

Details

Engineering Computations, vol. 12 no. 3
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 20 June 2019

Huijin Xu, Yan Wang and Xingchao Han

Phase change energy storage is an important solution for overcoming human energy crisis. This study aims to present an evaluation for the thermal performances of a phase…

Abstract

Purpose

Phase change energy storage is an important solution for overcoming human energy crisis. This study aims to present an evaluation for the thermal performances of a phase change material (PCM) and a PCM–metal foam composite. Effects of pore size, pore density, thermal conductivity of solid structure and mushy region on the thermal storage process are examined.

Design/methodology/approach

In this paper, temperature, flow field and solid–liquid interface of a PCM with or without porous media were theoretically assessed. The influences of basic parameters on the melting process were analyzed. A PCM thermal storage device with a metal foam composite is designed and a thermodynamic analysis for it is conducted. The optimal PCM temperature and the optimal HTF temperature in the metal foam-enhanced thermal storage device are derived.

Findings

The results show that the solid–liquid interface of pure PCM is a line area and that of the mixture PCM is a mushy area. The natural convection in the melting liquid is intensive for a PCM without porous medium. The porous medium weakens the natural convection and makes the temperature field, flow field and solid–liquid interface distribution more homogeneous. The metal foam can greatly improve the heat storage rate of a PCM.

Originality/value

Thermal storage rate of a PCM is compared with that of a PCM–metal foam composite. A thermal analysis is performed on the multi-layered parallel-plate thermal storage device with a PCM embedded in a highly conductive porous medium, and an optimal melting temperature is obtained with the exergy optimization. The heat transfer enhancement with metal foams proved to be necessary for the thermal storage application.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 27 June 2008

S. Kiwan and O. Zeitoun

The aim is to study the effects of fin conductivity ratio, Darcy number, and Rayleigh number on the average Nusselt number for fins made of porous material when attached…

Abstract

Purpose

The aim is to study the effects of fin conductivity ratio, Darcy number, and Rayleigh number on the average Nusselt number for fins made of porous material when attached to the inner cylinder of the annulus between two concentric cylinders. The paper also aims to compare the results with those obtained using solid fins over a range of Rayleigh numbers.

Design/methodology/approach

The Darcy‐Brinkman equations were used to model the fluid flow inside the porous media and the Boussinesq approximation was used to model the buoyancy effect. The energy equation is also solved to find the temperature distribution in the domain of interest. The model equations are solved numerically using a finite volume code.

Findings

Porous fins provided higher heat transfer rates than solid fins for similar configurations. This enhancement in heat transfer reached 75 per cent at Ra=5 × 104 and Da=2.5 × 10−2. It is also found that unlike solid fins the rate of heat transfer from the cylinder equipped with porous fins decreases with increasing the fin inclination angle.

Research limitations/implications

The range of the Rayleigh number considered in this research covers only the laminar regime. The research does not cover turbulent flows. In addition to that, the local thermal equilibrium assumption is used.

Practical implications

This work can help designers in selecting the proper material properties and operating conditions in designing porous fins to enhance the heat transfer in the annulus between two horizontal concentric cylinders under natural convection condition.

Originality/value

This work has not been done before and it can initiate additional research projects as looking at the performance of porous fins under other conditions and configurations (e.g. turbulent conditions).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 18 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 17 March 2012

Boqiong Li, Zhiqiang Li and Xing Lu

Porous titanium is used in many bioimplant and electrode applications because of its interconnected pore structure and good corrosion resistance. The purpose of this paper…

Abstract

Purpose

Porous titanium is used in many bioimplant and electrode applications because of its interconnected pore structure and good corrosion resistance. The purpose of this paper is to study the anodic polarization behavior of porous titanium in different electrolytes and clarify the influences of the porosity and macro‐pore size on the corrosion resistance.

Design/methodology/approach

The porous titanium with 10‐70% porosities and average macro‐pore sizes in the range of 100‐500 μm was prepared by the powder metallurgy method using polymethyl methacrylate (PMMA) as a space holder. Electrochemical corrosion tests were performed on porous titanium as well as solid titanium (with the same irregular and isolated micro‐pore structures as that on the interconnected spheroidal macro‐pore walls of porous titanium) in the 0.1 M H2SO4, 1 M NaOH and 0.9% NaCl (37 °C) solutions.

Findings

It was found that porous titanium exhibited an active‐passive transition behavior in the 1 M NaOH and 0.1 M H2SO4 solutions. In contrast, a self‐passivation transition behavior was observed in the 0.9% NaCl solution (37 °C).

Originality/value

The paper demonstrates that both the porosity and macro‐pore size of porous titanium play an important role in determining the corrosion rate, rather than the corrosion potential.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

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