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1

Free vibration analysis of imperfect functionally graded sandwich plates: analytical and experimental investigation

Njim E.K., Bakhy S.H., Al-Waily M.

Archives of Materials Science and Engineering

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2021

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Vol. 111, nr 2

49--65

EN

Purpose: This paper develops a new analytical solution to conduct the free vibration analysis of porous functionally graded (FG) sandwich plates based on classical plate theory (CPT). The sandwich plate made of the FGM core consists of one porous metal that had not previously been taken into account in vibration analysis and two homogenous skins. Design/methodology/approach: The analytical formulations were generated based on the classical plate theory (CPT). According to the power law, the material properties of FG plates are expected to vary along the thickness direction of the constituents. Findings: The results show that the porosity parameter and the power gradient parameter significantly influence vibration characteristics. It is found that there is an acceptable error between the analytical and numerical solutions with a maximum discrepancy of 0.576 % at a slenderness ratio (a/h =100), while the maximum error percentage between the analytical and experimental results was found not exceeding 15%. Research limitations/implications: The accuracy of analytical solutions is verified by the adaptive finite elements method (FEM) with commercial ANSYS 2020 R2 software. Practical implications: Free vibration experiments on 3D-printed FGM plates bonded with two thin solid face sheets at the top and bottom surfaces were conducted. Originality/value: The novel sandwich plate consists of one porous polymer core and two homogenous skins which can be widely applied in various fields of aircraft structures, biomedical engineering, and defense technology. This paper presents an analytical and experimental study to investigate the free vibration problem of a functionally graded simply supported rectangular sandwich plate with porosities. The objective of the current work is to examine the effects of some key parameters, such as porous ratio, power-law index, and slenderness ratio, on the natural frequencies and damping characteristics.

2

Design of Proven Technology of Metal Foam and Porous Metal Casting Production

Radkovský F., Merta V., Obzina T.

Archives of Foundry Engineering

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2021

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Vol. 21, iss. 1

125--131

EN

The article describes the design of a proven technology for the production of metal foam and porous metal by the foundry. Porous metal formed by infiltrating liquid metal into a mould cavity appears to be the fastest and most economical method. However, even here we cannot do without the right production parameters. Based on the research, the production process was optimised and subsequently a functional sample of metal foam with an irregular internal structure - a filter - was produced. The copper alloy filter was cast into a gypsum mould using an evaporable model. Furthermore, a functional sample of porous metal with a regular internal structure was produced - a heat exchanger. The aluminium alloy heat exchanger was cast into a green sand mould using preforms. Also, a porous metal casting with a regular internal structure was formed for use as an element in deformation zones. This aluminium alloy casting was made by the Lost Foam method. The aim is therefore to ensure the production of healthy castings, which would find use in the field of filtration of liquid metal or flue gases, in vehicles in the field of shock energy absorption and also in energy as a heat exchanger.

3

Effect of Powder Shape and Sintering Temperature on the Preparation of Ni-Based Porous Metal

Yi Yu-Jeong, Lee Min-Jeong, Kim Hyeon-Ju, Yang Sangsun, Park Man-Ho, Kim Byoung-Kee, Yun Jung-Yeul

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 3

917--920

EN

Usually porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability for exhaust gas filter, hydrogen reformer catalyst support. The Ni alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. In this study, the Ni-based porous metals have been developed with Hastelloy powder by gas atomization and water atomization in order to find the effects of powder shape on porous metal. Each Hastelloy powder is pressed on disk shape of 2 mm thickness with 12 tons using uniaxial press machine. The specimens are sintered at various temperatures in high vacuum condition. The pore properties were evaluated using Porometer and microstructures were observed with SEM.

4

A Study on Pore Properties of Hastelloy Powder Porous Metal Fabricated by Electrostatic Powder Coating

Lee Min-Jeong, Yi Yu-Jeong, Kim Hyeon-Ju, Park Man-Ho, Kim Byoung-Kee, Yun Jung-Yeul

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 2

547--550

EN

Porous metals show not only extremely low density, but also excellent physical, mechanical and acoustic properties. In this study, Hastelloy powders prepared by gas atomization are used to manufacture 3D geometries of Hastelloy porous metal with above 90% porosity using electrostatic powder coating process. In order to control pore size and porosity, foam is sintered at 1200~1300°C and different powder coating amount. The pore properties are evaluated using SEM and Archimedes method. As powder coating amount and sintering temperature increased, porosity is decreased from 96.4 to 94.4%. And foam density is increased from 0.323 to 0.497 g/cm3 and pore size is decreased from 98 to 560 μm. When the sintering temperature is increased, foam thickness and strut thickness are decreased from 9.85 to 8.13 mm and from 366 to 292 μm.

5

CO Oxidation Properties Of Selective Dissoluted Metallic Glass Composites

Kim S. Y., Lee M. H., Kim T. S., Kim B. S.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1227--1229

EN

Porous metallic materials have been widely used in many fields including aerospace, atomic energy, electro chemistry and environmental protection. Their unique structures make them very useful as lightweight structural materials, fluid filters, porous electrodes and catalyst supports. In this study, we fabricated Ni-based porous metallic glasses having uniformly dispersed micro meter pores by the sequential processes of ball-milling and chemical dissolution method. We investigated the application of our porous metal supported for Pt catalyst. The oxidation test was performed in an atmosphere of 1% CO and 3% O2. Microstructure observation was performed by using a scanning electron microscope. Oxidation properties and BET (Brunauer, Emmett, and Teller) were analyzed to understand porous structure developments. The results indicated that CO Oxidation reaction was dependent on the specific surface area.

6

Critical state of an isotropic porous cylindrical panel

Malinowski M.

International Journal of Applied Mechanics and Engineering

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2008

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Vol. 13, no 4

955-965

EN

This paper presents a study of elastic buckling of a porous cylindrical panel subjected to axial compression or pressure. The material of the panel is made of an isotropic porous metal. Porosity of the metal varies across the thickness of the panel with its mechanical properties varying accordingly. The modulus of elasticity is minimal on the middle surface of the cylindrical panel and takes maximal values at its top and bottom surfaces. A nonlinear hypothesis of deformation of a plane cross section of the shell is assumed. Based on the theorem of minimum total potential energy the system of differential equations and suitable boundary conditions are obtained. The system is solved analytically and critical load and pressure are determined. Results of the solution, i.e., The critical load and critical pressure of selected shells by means of the FEM (ANSYS) are verified.