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1

Analytical and numerical flexural properties of polymeric porous functionally graded (PFGM) sandwich beams

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

Journal of Achievements in Materials and Manufacturing Engineering

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2022

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Vol. 110, nr 1

5--15

EN

Purpose: Materials with porosity gradient functionally gradient properties reflect changes in the material's position spatially in response to changes in porosity. One porous metal comprised the FGM core and had not previously been considered in bending analyses. Design/methodology/approach: Analytical formulations were derived based on the classical beam theory (CBT). According to the power-law scheme, the material properties of FG beams are supposed to vary along the thickness direction of the constituents. Findings: The results show that the porosity and power gradient parameters significantly influence flexural bending characteristics. It is found that there is a fair agreement between the analytical and numerical results, with a maximum error percentage not exceeding 5%. Research limitations/implications: The accuracy of analytical solutions is verified by employing the finite elements method (FEM) with commercial ANSYS 2021 R1 software. Practical implications: FGM beams' elastic properties with an even porosity distribution through-beam core and bonded with two thin solid skins at the upper and lower surfaces were carried out. Originality/value: This paper develops an analytical study to investigate the flexural problem of a functionally graded simply supported sandwich beam with porosities widely used in aircraft structures and biomedical engineering. The objective of the current work is to examine the effects of some key parameters, such as porous ratio, power-law index, and core metal type, on the flexural properties such as bending load, total deformation, and strain energy.

2

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.

3

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.

4

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.