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경사기능 복합재료 판의 기계적 강도해석 (Mechanical strength analysis for functionally graded composite plates)

  • 나경수;김지환
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2005년도 추계학술발표대회 논문집
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    • pp.66-69
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    • 2005
  • Mechanical strength of functionally graded composite plates that composed of ceramic, functionally graded material and metal layers is investigated using 3-D finite element method. In FGM layer, material properties are assumed to be varied continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of a ceramic and metal. The 3-D finite element model is adopted by using an IS-node solid element to analyze more accurately the variation of material properties in the thickness direction. Numerical results are compared with those of the previous works. In addition, the displacements, the tensile stresses and the compressive stresses are analyzed for the variation of FGM thickness ratio and volume fraction distribution.Mechanical strength of functionally graded composite plates that composed of ceramic, functionally graded material and metal layers is investigated using 3-D finite element method. In FGM layer, material properties are assumed to be varied continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of a ceramic and metal. The 3-D finite element model is adopted by using an IS-node solid element to analyze more accurately the variation of material properties in the thickness direction. Numerical results are compared with those of the previous works. In addition, the displacements, the tensile stresses and the compressive stresses are analyzed for the variation of FGM thickness ratio and volume fraction distribution.

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Free vibration analysis of bidirectional functionally graded annular plates resting on elastic foundations using differential quadrature method

  • Tahouneh, Vahid
    • Structural Engineering and Mechanics
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    • 제52권4호
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    • pp.663-686
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    • 2014
  • This paper deals with free vibration analysis of bidirectional functionally graded annular plates resting on a two-parameter elastic foundation. The formulations are based on the three-dimensional elasticity theory. This study presents a novel 2-D six-parameter power-law distribution for ceramic volume fraction of 2-D functionally graded materials that gives designers a powerful tool for flexible designing of structures under multi-functional requirements. Various material profiles along the thickness and in the in-plane directions are illustrated by using the 2-D power-law distribution. The effective material properties at a point are determined in terms of the local volume fractions and the material properties by the Mori-Tanaka scheme. The 2-D differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and to implement the boundary conditions. The fast rate of convergence of the method is shown and the results are compared against existing results in literature. Some new results for natural frequencies of the plates are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The interesting results indicate that a graded ceramic volume fraction in two directions has a higher capability to reduce the natural frequency than conventional 1-D functionally graded materials.

Free vibration analysis of functionally graded cylindrical shells with different shell theories using semi-analytical method

  • Khayat, Majid;Dehghan, Seyed Mehdi;Najafgholipour, Mohammad Amir;Baghlani, Abdolhossein
    • Steel and Composite Structures
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    • 제28권6호
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    • pp.735-748
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    • 2018
  • In this study, the semi-analytical finite strip method is adopted to examine the free vibration of cylindrical shells made up of functionally graded material. The properties of functionally graded shells are assumed to be temperature-dependent and vary continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of ceramic and metal. The material properties of the shells and stiffeners are assumed to be continuously graded in the thickness direction. Theoretical formulations based on the smeared stiffeners technique and the classical shell theory with first-order shear deformation theory which accounts for through thickness shear flexibility are employed. The finite strip method is applied to five different shell theories, namely, Donnell, Reissner, Sanders, Novozhilov, and Teng. The approximate procedure is compared favorably with three-dimensional finite elements. Finally, a detailed numerical study is carried out to bring out the effects of power-law index of the functional graded material, stiffeners, and geometry of the shells on the difference between various shell theories. Finally, the importance of choosing the shell theory in simulating the functionally graded cylindrical shells is addressed.

Fracture analysis of functionally graded beams with considering material non-linearity

  • Rizov, Victor I.
    • Structural Engineering and Mechanics
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    • 제64권4호
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    • pp.487-494
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    • 2017
  • The present paper deals with a theoretical study of delamination fracture in the Crack Lap Shear (CLS) functionally graded beam configuration. The basic purpose is to analyze the fracture with taking into account the material non-linearity. The mechanical behavior of CLS was described by using a non-linear stress-strain relation. It was assumed that the material is functionally graded along the beam height. The fracture was analyzed by applying the J-integral approach. The curvature and neutral axis coordinate of CLS beam were derived in order to solve analytically the J-integral. The non-linear solution of J-integral obtained was verified by analyzing the strain energy release rate with considering material non-linearity. The effects of material gradient, crack location along the beam height and material non-linearity on fracture behavior were evaluated. The J-integral non-linear solution derived is very suitable for parametric studies of longitudinal fracture in the CLS beam. The results obtained can be used to optimize the functionally graded beam structure with respect to the fracture performance. The analytical approach developed in the present paper contributes for the understanding of delamination fracture in functionally graded beams exhibiting material non-linearity.

Influence of porosity and axial preload on vibration behavior of rotating FG nanobeam

  • Ehyaei, Javad;Akbarshahi, Amir;Shafiei, Navvab
    • Advances in nano research
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    • 제5권2호
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    • pp.141-169
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    • 2017
  • In this paper, a nanobeam connected to a rotating molecular hub is considered. The vibration behavior of rotating functionally graded nanobeam based on Eringen's nonlocal theory and Euler-Bernoulli beam model is investigated. Furthermore, axial preload and porosity effect is studied. It is supposed that the material attributes of the functionally graded porous nanobeam, varies continuously in the thickness direction according to the power law model considering the even distribution of porosities. Porosity at the nanoscopic length scale can affect on the rotating functionally graded nanobeams dynamics. The equations of motion and the associated boundary conditions are derived through the Hamilton's principle and generalized differential quadrature method (GDQM) is utilized to solve the equations. In this paper, the influences of some parameters such as functionally graded power (FG-index), porosity parameter, axial preload, nonlocal parameter and angular velocity on natural frequencies of rotating nanobeams with pure ceramic, pure metal and functionally graded materials are examined and some comparisons about the influence of various parameters on the natural frequencies corresponding to the simply-simply, simplyclamped, clamped-clamped boundary conditions are carried out.

Thermal bending analysis of functionally graded thick sandwich plates including stretching effect

  • Mohammed Sid Ahmed Houari;Aicha Bessaim;Smain Bezzina;Abdelouahed Tounsi
    • Structural Engineering and Mechanics
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    • 제86권3호
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    • pp.373-384
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    • 2023
  • The main objective of this research work is to present analytical solutions for the thermoelastic bending analysis of sandwich plates made of functionally graded materials with an arbitrary gradient. The governing equations of equilibrium are solved for a functionally graded sandwich plates under the effect of thermal loads. The transverse shear and normal strain and stress effects on thermoelastic bending of such sandwich plates are considered. Field equations for functionally graded sandwich plates whose deformations are governed by either the shear deformation theories or the classical theory are derived. Displacement functions that identically satisfy boundary conditions are used to reduce the governing equations to a set of coupled ordinary differential equations with variable coefficients. The results of the shear deformation theories are compared together. Numerical results for deflections and stresses of functionally graded metal-ceramic plates are investigated.

A quasi-3D nonlocal theory for free vibration analysis of functionally graded sandwich nanobeams on elastic foundations

  • Mofareh Hassan Ghazwani;Ali Alnujaie;Pham Van Vinh;Abdelouahed Tounsi
    • Advances in nano research
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    • 제16권3호
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    • pp.313-324
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    • 2024
  • The main aims of this study are to develop a new nonlocal quasi-3D theory for the free vibration behaviors of the functionally graded sandwich nanobeams. The sandwich beams consist of a ceramic core and two functionally graded material layers resting on elastic foundations. The two layers, linear spring stiffness and shear layer, are used to model the effects of the elastic foundations. The size-effect is considered using nonlocal elasticity theory. The governing equations of the motion of the functionally graded sandwich nanobeams are obtained via Hamilton's principle in combination with nonlocal elasticity theory. Then the Navier's solution technique is used to solve the governing equations of the motion to achieve the nonlocal free vibration behaviors of the nanobeams. A deep parametric study is also provided to demonstrate the effects of some parameters, such as length-to-height ratio, power-law index, nonlocal parameter, and two parameters of the elastic foundation, on the free vibration behaviors of the functionally graded sandwich nanobeams.

Analysis of the hygro-thermo-mechanical response of functionally graded plates resting on elastic foundations based on various micromechanical models

  • Belkacem Adim;Tahar Hassaine Daouadji
    • Geomechanics and Engineering
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    • 제38권4호
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    • pp.409-420
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    • 2024
  • In this research the hygro-thermo-mechanical loading and micromechanical model effects on bending behavior of functionally graded material plates resting on Winkler and Pasternak elastic foundations, the higher order shear deformation theory is used here. The material properties of the plate: young's modulus, thermal coefficient and moisture expansion coefficient are assumed to be graded in the thickness direction according to various micromechanical models starting with the Voigt's model which is commonly used in most functionally graded plates studies to the Reuss's, LRVE's and Mori-Tanaka's models. The principle of virtual displacement is used to determine the equilibrium equations and the a several numerical results are given to validate the precision of the present method for bending behavior of FGM plates subjected to hygro-thermo-mechanical loading resting on elastic foundations. Afterwards, a parametric study is conducted to determine the effect of different parameters on the deflection of the FGM plates like micromechanical models, type of loading and plate geometry. In the lights of the present research, it can be concluded that the present theory is accurate and simple in predicting the deflection behavior of functionally graded plates under hygro-thermo-mechanical effects and micromechanical models.

HVPE 방법에 의해 성장된 graded AlGaN 에피층의 특성 (Characterizations of graded AlGaN epilayer grown by HVPE)

  • 이찬빈;전헌수;이찬미;전인준;양민;이삼녕;안형수;김석환;유영문
    • 한국결정성장학회지
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    • 제25권2호
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    • pp.45-50
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    • 2015
  • 본 논문에서는 Al 조성이 점진적으로 변화된 AlGaN 에피층을 HVPE (hydride vapor phase epitaxy) 방법에 의하여 성장하였다. 소스영역의 온도는 $950^{\circ}C$, 성장 영역의 온도는 $1145^{\circ}C$에서 연속적으로 (0001) 사파이어 기판위에 성장되었고, AlGaN 에피층은 시간당 100 nm의 성장률을 보였다. FE-SEM 측정과 EDS 측정으로부터 성장층의 Al 변화를 확인하였으며, AFM 측정결과 2인치 기판위에 성장된 graded AlGaN 에피층의 거칠기는 수십 nm였다. Al 조성의 변화는 XRD 측정에 의하여 확인하였으며, Al 조성 74 %의 (002) AlGaN의 주피크 관측과 함께 연속적으로 (002) AlN 층의 피크가 확인되었다. 이는 하나의 층에 사파이어 기판으로부터 Al 조성이 점진적으로 변화하는 에피층을 HVPE 방법으로 얻었음을 증명하며, 이 결과로부터 다양한 광소자 및 전자소자의 응용이 기대된다.

노인장기요양보험 등급외자의 등급유지 영향요인 분석 (A Study of Factors Affecting the Grade Maintenance of the non-graded of Long-Term Care Insurance)

  • 서수진;문용필
    • 한국콘텐츠학회논문지
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    • 제20권7호
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    • pp.149-160
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    • 2020
  • 본 연구는 노인장기요양보험 등급외자의 특성을 파악하고 등급유지 영향요인을 분석하여, 그들의 지속적 재가생활을 위한 정책제언을 제시하는 것에 목적이 있다. 이를 위해 국민건강보험공단의 장기요양 인정조사 및 급여자료를 활용하여 등급외자의 등급외 유지여부에 영향을 미치는 관련요인을 분석하였다. 분석결과는 다음과 같다. 등급외자의 등급외 유지와 관련하여 소인성 요인에서 연령이 낮을수록, 남성이 여성보다 등급외 상태를 유지할 확률이 높게 나타났다. 촉진요인에서는 독거노인이 가족과 동거하는 노인에 비해, 국민기초생활수급권자가 일반대상자보다 등급외 상태를 유지할 확률이 높게 나타났다. 욕구요인에서 치매가 없는 자가 치매가 있는 자에 비해, 최초 판정받은 등급이 낮을수록, 등급판정 재신청 횟수가 낮을수록 등급외 상태를 유지할 확률이 높게 나타났다. 이상의 연구결과에 기초하여 등급외자의 장기요양서비스 제도개선에 대한 정책적 시사점을 제시하였다.