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1
Content available remote Zastosowanie metody elementów brzegowych dla środowisk niejednorodnych na przykładzie badania zawilgocenia murów
100%
Pańczyk M. , Sikora J.
Zeszyty Naukowe. Elektryka / Politechnika Łódzka
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2015
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tom z. 126
117--124
PL
Artykuł prezentuje opis matematyczny implementacji środowisk niejednorodnych w metodzie elementów brzegowych. Wyniki obliczeń porównane są z realnymi pomiarami zawilgocenia zbudowanego w warunkach laboratoryjnych muru, wykonanymi z użyciem 26 elektrodowego tomografu impedancyjnego i klasycznej metody suszarkowo-wagowej.
EN
The boundary element method implementation used to find tomographic image of damped wall humidity distribution is presented. Damped wall represents nonhomogeneous media where humidity has a spatial distribution that varies with two coordinates. Real measurements were taken and function coefficients where found using boundary element method, verified again by finite element method.
2
Content available Free vibration analysis of imperfect functionally graded sandwich plates: analytical and experimental investigation
84%
Njim E. K. , Bakhy S. H. , Al-Waily M.
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2021
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tom 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
Content available Calculation of Stress Intensity Factor for an Internal Circumferential Crack in a Rotating Functionally Graded Thick-Walled Hollow Circular Cylinder under Thermal Shock
84%
Ghafoor E. M. R. , Rokhi M. M.
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tom Vol. LXIV, nr 4
455--479
EN
In this article, the fracture behavior of functionally graded thick-walled cylinder under thermo-mechanical shock is investigated. For this purpose, classical coupled thermoelastic equations are used in calculations. First, these equations are discretized with extended finite element method (XFEM) in the space domain and then they are solved by the Newmark method in the time domain. The most general form of interaction integral is extracted for axially symmetric circumferential crack in a cylinder under thermal and mechanical loads in functionally graded materials and is used to calculate dynamic stress intensity factors (SIFs). The problem solution has been implemented in MATLAB software.
4
Content available remote Characterization of the starting materials for functionally graded thermoelectric materials for pseudobinary system of Bi2Te3-Sb2Te3
84%
Januszko K. , Chetty R. , Mashimo T. , Wojciechowski K. T.
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2016
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tom R. 89, nr 5-6
522--523
EN
Samples of Bi-Sb-Te system were prepared by solid state synthesis from pure elements, microstructure and thermoelectric properties were characterized. From obtained powders segmented samples were construct-ed in order to confirm change of the thermoelectric properties with composition. Segmented element is expected to have better efficiency.
PL
Próbki otrzymane w wyniku syntezy z czystych pier-wiastków zostały scharakteryzowane pod względem mikrostruktury i właściwości termoelektrycznych. Z otrzymanych proszków skonstruowano element seg-mentowy i potwierdzono zmianę właściwości termoelektrycznych ze zmianą składu chemicznego. Przewiduje się podwyższoną sprawność takiego elementu.
5
Content available Finite element formulation for the large-amplitude vibrations of FG beams
67%
Javid M. , Hemmatnezhad M.
Archive of Mechanical Engineering
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2014
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tom Vol. LXI, nr 3
469--482
EN
On the basis of Euler-Bernoulli beam theory, the large-amplitude free vibration analysis of functionally graded beams is investigated by means of a finite element formulation. The von Kármán type nonlinear strain-displacement relationship is employed where the ends of the beam are constrained to move axially. The material properties are assumed to be graded in the thickness direction according to the powerlaw and sigmoid distributions. The finite element method is employed to discretize the nonlinear governing equations, which are then solved by the direct numerical integration technique in order to obtain the nonlinear vibration frequencies of functionally graded beams with different boundary conditions. The influences of power-law index, vibration amplitude, beam geometrical parameters and end supports on the free vibration frequencies are studied. The present numerical results compare very well with the results available from the literature where possible.
PL
W oparciu o teorię Eulera-Bernouliego przeprowadzono analizę wielkoamplitudowych drgań belki gradientowej posługując się metodą elementów skończonych. Związek między odkształceniem i przemieszczeniem, typu von Kármána, zastosowano tam, gdzie końce belki są utwierdzone i mogą poruszać się osiowo. Zakłada się, że właściwości materiału zmieniają się w kierunku poprzecznym (grubości) zgodnie z funkcją potęgową lub sigmoidalną. Metoda elementów skończonych jest zastosowana w celu dyskretyzacji nieliniowych równań sterujących, z których po rozwiązywaniu metodą bezpośredniego całkowania numerycznego wyznacza się częstotliwości drgań nieliniowych belki gradientowej dla różnych warunków brzegowych. Badany jest wpływ wykładnika funkcji, amplitudy drgań, geometrycznych parametrów belki i podparcia końców na częstotliwości drgań swobodnych. Wyniki numeryczne, przedstawione w artykule, zgadzają się dobrze z wynikami podawanymi w dostępnej literaturze.
6
Content available remote Numerical analysis of fracture behavior of functionally graded materials using 3D-XFEM
67%
Benhamena A. , Fatima B. , Foudil K. , Baltach A. , Chaouch M. I.
Advances in Materials Science
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2023
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tom Vol. 23, nr 3(77)
33--46
EN
This paper presents the numerical evaluation of mixed stress intensity factors (SIFs) and non-singular terms of William's series (T-stress) of functionally graded materials (FGMs) using three-dimensional extended finite element method (3D-XFEM). Four-point bending specimen with crack perpendicular to material gradation have been used in this investigation in order to study the effect of some parameters (crack position, crack size, specimen thickness) on the failure of FGMs materials. The fracture parameters (KI KII, phase angle ψ and T-stress) obtained by the present simulation are compared with available experimental and numerical results. An excellent correlation was found of the 3D-XFEM simulations with those available in the literature. From the numerical results, a fitting procedure is performed in order to propose an analytical formulation and subsequently are validated against the 3D-XFEM results.
7
Content available Elastic and Viscoelastic Stresses of Nonlinear Rotating Functionally Graded Solid and Annular Disks with Gradually Varying Thickness
67%
Allam M. N. M. , Tantawy R. , Yousof A. , Zenkour A. M.
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tom Vol. LXIV, nr 4
423--440
EN
Analytical and numerical nonlinear solutions for rotating variable-thickness functionally graded solid and annular disks with viscoelastic orthotropic material properties are presented by using the method of successive approximations.Variable material properties such as Young’s moduli, density and thickness of the disk, are first introduced to obtain the governing equation. As a second step, the method of successive approximations is proposed to get the nonlinear solution of the problem. In the third step, the method of effective moduli is deduced to reduce the problem to the corresponding one of a homogeneous but anisotropic material. The results of viscoelastic stresses and radial displacement are obtained for annular and solid disks of different profiles and graphically illustrated. The calculated results are compared and the effects due to many parameters are discussed.
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