• 제목/요약/키워드: graded

검색결과 2,494건 처리시간 0.021초

A new five unknown quasi-3D type HSDT for thermomechanical bending analysis of FGM sandwich plates

  • Benbakhti, Abdeldjalil;Bouiadjra, Mohamed Bachir;Retiel, Noureddine;Tounsi, Abdelouahed
    • Steel and Composite Structures
    • /
    • 제22권5호
    • /
    • pp.975-999
    • /
    • 2016
  • This work investigates a thermomechanical bending analysis of functionally graded sandwich plates by proposing a novel quasi-3D type higher order shear deformation theory (HSDT). The mathematical model introduces only 5 variables as the first order shear deformation theory (FSDT). Unlike the conventional HSDT, the present one presents a novel displacement field which includes undetermined integral variables. The mechanical properties of functionally graded layers of the plate are supposed to change in the thickness direction according to a power law distribution. The core layer is still homogeneous and made of an isotropic ceramic material. The governing equations for the thermomechanical bending investigation are obtained through the principle of virtual work and solved via Navier-type method. Interesting results are determined and compared with quasi-3D and 2D HSDTs. The influences of functionally graded material (FGM) layer thickness, power law index, layer thickness ratio, thickness ratio and aspect ratio on the deflections and stresses of functionally graded sandwich plates are discussed.

균열이 있는 기능경사 압전 세라믹의 충격 특성에 관한 연구 (Transient Response of Functionally Graded Piezoelectric Ceramic with Crack)

  • Jeong Woo Shin;Tae-Uk Kim;Sung Chan Kim
    • Composites Research
    • /
    • 제16권5호
    • /
    • pp.21-27
    • /
    • 2003
  • 선형 압전 이론(theory of linear piezoelectricity)을 이용하여 면외전단 충격(anti-plane shear impact)을 받는 기능경사 압전 세라믹(functionally graded piezoelectric ceramic)의 중앙에 존재하는 균열(central crack)의 동적 응답에 대해 연구한다. 기능경사 압전재료의 물성치(material property)는 두께방향을 따라 연속적으로 변한다고 가정한다. 라플라스 변환(Laplace transform)과 푸리에 변환(Fourier transform)을 사용하여 두 쌍의 복합적분 방정식을 구성하며, 이를 제2종 Fredholm 적분 방정식(Fredholm integral equations of the second kind)으로 표현한다. 재료 물성치의 변화도(gradient of material properties)와 전기하중(electric loading)의 영향을 보기 위해 동응력세기계수(dynamic stress intensity factor)에 대한 수치 결과를 제시하였다.

Dynamic behavior of a functionally graded plate resting on Winkler elastic foundation and in contact with fluid

  • Shafiee, Ali A.;Daneshmand, Farhang;Askari, Ehsan;Mahzoon, Mojtaba
    • Structural Engineering and Mechanics
    • /
    • 제50권1호
    • /
    • pp.53-71
    • /
    • 2014
  • A semi-analytical method is developed to consider free vibrations of a functionally graded elastic plate resting on Winkler elastic foundation and in contact with a quiescent fluid. Material properties are assumed to be graded distribution along the thickness direction according to a power-law in terms of the volume fractions of the constituents. The fluid is considered to be incompressible and inviscid. In the analysis, the effect of an in-plane force in the plate due to the weight of the fluid is taken into account. By satisfying the compatibility conditions along the interface of fluid and plate, the fluid-structure interaction is taken into account and natural frequencies and mode shapes of the coupled system are acquired by employing energy methods. The results obtained from the present approach are verified by those from a finite element analysis. Besides, the effects of volume fractions of functionally graded materials, Winkler foundation stiffness and in-plane forces on the dynamic of plate are elucidated.

A new higher-order shear and normal deformation theory for functionally graded sandwich beams

  • Bennai, Riadh;Atmane, Hassen Ait;Tounsi, Abdelouahed
    • Steel and Composite Structures
    • /
    • 제19권3호
    • /
    • pp.521-546
    • /
    • 2015
  • A new refined hyperbolic shear and normal deformation beam theory is developed to study the free vibration and buckling of functionally graded (FG) sandwich beams under various boundary conditions. The effects of transverse shear strains as well as the transverse normal strain are taken into account. Material properties of the sandwich beam faces are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. Equations of motion are derived from Hamilton's principle. Analytical solutions for the bending, free vibration and buckling analyses are obtained for simply supported sandwich beams. Illustrative examples are given to show the effects of varying gradients, thickness stretching, boundary conditions, and thickness to length ratios on the bending, free vibration and buckling of functionally graded sandwich beams.

SPS/용침 공정에 의한 W-Cu연속경사기능재료의 제초와 특성 (Fabrication and Characteristics of Continuous W-Cu FGM by SPS/Infiltration Process)

  • 신철균;석명진;오승탁;김지순;권영순
    • 한국분말재료학회지
    • /
    • 제11권2호
    • /
    • pp.158-164
    • /
    • 2004
  • W-Cu composite has been used for the applications requiring both high strength, good thermal and electrical conductivity. A graded combination of W and Cu will reduce thermal stress concerned with heat conduction, maintaining good thermal conductivity and high mechanical strength. In the present work, an attempt was made to fabricate continuous W-Cu FGM by preparing the graded porous structure of W skeleton using spark plasma sintering (SPS) process followed by infiltrating Cu. The graded porous structure was prepared at 150$0^{\circ}C$ for 60s under pressure of 15MPa by SPS process using a graphite mold with varying crr)ss section in the longitudinal direction. Infiltration of Cu was performed at 115$0^{\circ}C$ for 1 hour under $H_2$. W-Cu composite with graded Cu composition of 14 to 27 wt% was finally prepared. In this process the gradient of composition could be conveniently controlled by varying the gradient of cross sectional area of graphite mold, temperature and pressure.

A simple analytical approach for thermal buckling of thick functionally graded sandwich plates

  • El-Haina, Fouzia;Bakora, Ahmed;Bousahla, Abdelmoumen Anis;Tounsi, Abdelouahed;Mahmoud, S.R.
    • Structural Engineering and Mechanics
    • /
    • 제63권5호
    • /
    • pp.585-595
    • /
    • 2017
  • This study aimed to presents a simple analytical approach to investigate the thermal buckling behavior of thick functionally graded sandwich by employing both the sinusoidal shear deformation theory and stress function. The material properties of the sandwich plate faces are continuously varied within the plate thickness according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are considered as uniform, linear and non-linear temperature rises across the thickness direction. Numerical examples are presented to prove the effect of power law index, loading type and functionally graded layers thickness on the thermal buckling response of thick functionally graded sandwich.

A novel and simple HSDT for thermal buckling response of functionally graded sandwich plates

  • Elmossouess, Bouchra;Kebdani, Said;Bouiadjra, Mohamed Bachir;Tounsi, Abdelouahed
    • Structural Engineering and Mechanics
    • /
    • 제62권4호
    • /
    • pp.401-415
    • /
    • 2017
  • A new higher shear deformation theory (HSDT) is presented for the thermal buckling behavior of functionally graded (FG) sandwich plates. It uses only four unknowns, which is even less than the first shear deformation theory (FSDT) and the conventional HSDTs. The theory considers a hyperbolic variation of transverse shear stress, respects the traction free boundary conditions and contrary to the conventional HSDTs, the present one presents a new displacement field which includes undetermined integral terms. Material characteristics and thermal expansion coefficient of the sandwich plate faces are considered to be graded in the thickness direction according to a simple power-law distribution in terms of the volume fractions of the constituents. The core layer is still homogeneous and made of an isotropic material. The thermal loads are supposed as uniform, linear and non-linear temperature rises within the thickness direction. An energy based variational principle is used to derive the governing equations as an eigenvalue problem. The validation of the present work is carried out with the available results in the literature. Numerical results are presented to demonstrate the influences of variations of volume fraction index, length-thickness ratio, loading type and functionally graded layers thickness on nondimensional thermal buckling loads.

Free vibration analysis of functionally graded beams with variable cross-section by the differential quadrature method based on the nonlocal theory

  • Elmeiche, Noureddine;Abbad, Hichem;Mechab, Ismail;Bernard, Fabrice
    • Structural Engineering and Mechanics
    • /
    • 제75권6호
    • /
    • pp.737-746
    • /
    • 2020
  • This paper attempts to investigate the free vibration of functionally graded material beams with nonuniform width based on the nonlocal elasticity theory. The theoretical formulations are established following the Euler-Bernoulli beam theory, and the governing equations of motion of the system are derived from the minimum total potential energy principle using the nonlocal elasticity theory. In addition, the Differential Quadrature Method (DQM) is applied, along with the Chebyshev-Gauss-Lobatto polynomials, in order to determine the weighting coefficient matrices. Furthermore, the effects of the nonlocal parameter, cross-section area of the functionally graded material (FGM) beam and various boundary conditions on the natural frequencies are examined. It is observed that the nonlocal parameter and boundary conditions significantly influence the natural frequencies of the functionally graded material beam cross-section. The results obtained, using the Differential Quadrature Method (DQM) under various boundary conditions, are found in good agreement with analytical and numerical results available in the literature.

레이저 직접 용융 시 금속분말의 함량조정을 통한 경사물성 부여 (Functionally Graded Properties Induced by Direct Laser Melting of Compositionally Selected Metallic Powders)

  • 한상욱;지원종;이철환;문영훈
    • 소성∙가공
    • /
    • 제23권5호
    • /
    • pp.303-310
    • /
    • 2014
  • Functionally graded properties are characterized by the gradual variation in composition and structure through the volume of the material, resulting in corresponding gradation in properties of the material. Direct laser melting (DLM) is a prototyping process whereby a 3-D part is built layer-wise by melting metal powder with laser scanning. Studies have been performed on the functionally graded properties induced by direct laser melting of compositionally selected metallic powders. For the current study, quadrangle structures were fabricated by DLM using Fe-Ni-Cr powders having variable compositions. Hardness and EDX analysis were conducted on cross-sections of the fabricated structure to characterize the properties. From the analysis, it is shown that functionally graded properties can be successfully obtained by DLM of selected metallic powders with varying compositions.

Non-linear analysis of dealamination fracture in functionally graded beams

  • Rizov, Victor I.
    • Coupled systems mechanics
    • /
    • 제6권1호
    • /
    • pp.97-111
    • /
    • 2017
  • The present paper reports an analytical study of delamination fracture in the Mixed Mode Flexure (MMF) functionally graded beam with considering the material non-linearity. The mechanical behavior of MMF beam is modeled by using a non-linear stress-strain relation. It is assumed that the material is functionally graded along the beam height. Fracture behavior is analyzed by the J-integral approach. Non-linear analytical solution is derived of the J-integral for a delamination located arbitrary along the beam height. The J-integral solution derived is verified by analyzing the strain energy release rate with considering the non-linear material behavior. The effects of material gradient, crack location along the beam height and material non-linearity on the fracture are evaluated. It is found that the J-integral value decreases with increasing the upper crack arm thickness. Concerning the influence of material gradient on the non-linear fracture, the analysis reveals that the J-integral value decreases with increasing the ratio of modulus of elasticity in the lower and upper edge of the beam. It is found also that non-linear material behavior leads to increase of the J-integral value. The present study contributes for the understanding of fracture in functionally graded beams that exhibit material non-linearity.