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Apetre, Nicoleta Alina. "Sandwich panels with functionally graded core." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012061.
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Soncco, K., X. Jorge, and R. A. Arciniega. "Postbuckling Analysis of Functionally Graded Beams." Institute of Physics Publishing, 2019. http://hdl.handle.net/10757/625602.
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This paper studies the geometrically non-linear bending behavior of functionally graded beams subjected to buckling loads using the finite element method. The computational model is based on an improved first-order shear deformation theory for beams with five independent variables. The abstract finite element formulation is derived by means of the principle of virtual work. High-order nodal-spectral interpolation functions were utilized to approximate the field variables which minimizes the locking problem. The incremental/iterative solution technique of Newton's type is implemented to solve the nonlinear equations. The model is verified with benchmark problems available in the literature. The objective is to investigate the effect of volume fraction variation in the response of functionally graded beams made of ceramics and metals. As expected, the results show that transverse deflections vary significantly depending on the ceramic and metal combination.Revisión por pares
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Heidari, Maryam. "3D modelling of functionally graded coatings." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215382.
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The purpose of this study is to investigate the behaviour of functionally graded materials in the coating design through analytical and numerical work. Functionally graded materials are advanced composite materials formed from two or more constituents with a continuously varying composition, which results in a continuous variation of material properties from one surface of the material to the other. The concept of functionally graded material is actively explored in coating design where structural and/or functional failures of the coating can happen due to a mismatch between the material properties of the coating and substrate, particularly at the coating/substrate interface. This work focuses on the performance of coated plates with homogeneous and graded coatings under various types of loading to develop a better understanding of their response. Firstly, the three dimensional elasticity solution for an isotropic coated plate with a stiffness gradient in the coating is extended to cover different types of applied loading and then a three dimensional elasticity solution for transversely isotropic materials with gradients in elastic properties is also developed. Based on the extended/developed solutions, a MATLAB code is created to produce a model that would enable the analysis of coated plates for a range of material, geometric and loading parameters. To test the analytical models, a finite element analysis is performed using the commercial finite element software ABAQUS, in which a user material subroutine is employed to generate a gradient in the material properties within each element and increase the accuracy of the results. All the developed analytical and numerical models are then used to carry out a comparative study of three-dimensional stress and displacement fields in the coated plates with homogeneous and graded coatings and establish the effect of various parameters such as coating thickness, coating position, plate dimensions, stiffness gradient, loading distributions and anisotropy on the coated plate response.
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Tilbrook, Matthew Thomas Materials Science & Engineering Faculty of Science UNSW. "Fatigue crack propagation in functionally graded materials." Awarded by:University of New South Wales. Materials Science & Engineering, 2005. http://handle.unsw.edu.au/1959.4/21885.
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Propagation of cracks in functionally graded materials (FGMs) under cyclic loading was investigated via experiments and finite element (FE) analysis. Alumina-epoxy composites with an interpenetrating-network structure and tailored spatial variation in composition were produced via a multi-step infiltration technique. Compressed polyurethane foam was infiltrated with alumina slip. After foam burn-out and sintering, epoxy was infiltrated into the porous alumina body. Non-graded specimens with a range of compositions were produced, and elastic properties and fatigue behaviour were characterised. An increase in crack propagation resistance under cyclic loading was quantified via a novel analytical approach. A simulation platform was developed with the commercial FE package ANSYS. Material gradient was applied via nodal temperature definitions. Stress intensity factors were calculated from nodal displacements near the crack-tip. Deflection criteria were compared and the local symmetry criterion provided the most accurate and efficient predictions. An automated mesh-redefinition algorithm enabled incremental simulation of crack propagation. Effects of gradient and crack-geometry parameters on crack-tip stresses were investigated, along with influences of crack-shape, crack-bridging, residual stresses and plasticity. The model provided predictions and data analysis for experimental specimens. Fatigue cracks in graded specimens deflected due to elastic property mismatch, concordant with FE predictions. In other FGMs, thermal or plastic properties may dominate deflection behaviour. Weaker step-interfaces influenced crack paths in some specimens; otherwise effects of toughness variation and gradient steps on crack path were negligible. Crack shape has an influence, but this is secondary to that of elastic gradient. Cracks in FGM specimens initially experienced increase in fatigue resistance with crack-extension followed by sudden decreases at step-interfaces. Bridging had a notable effect on crack propagation resistance but not on crack path. Similarly, crack paths did not differ between monotonic and cyclic loading, although crack-extension effects did. Recommendations for analysis and optimisation strategies for other FGM systems are given. Experimental characterization of FGMs is important, rather than relying on theoretical models. Opportunities for optimization of graded structures are limited by the properties of the constituent materials and resultant general crack deflection behaviour.
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Jivkov, Andrey P. "On crack growth in functionally graded materials." Licentiate thesis, Luleå tekniska universitet, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25814.
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Stress intensity factors' behaviour is studied for long plane cracks interacting with a region of functionally graded elastic material. The region is assumed embedded into a large body treated as a homogeneous elastic continuum. The analysis is limited to small deviations of the graded region's elastic modulus from that of the surrounding body (Poisson's ratio is kept constant) and analytical solutions are sought using a perturbation technique. Emphasis is laid on the case of an infinite strip, which admits a closed form solution. A cosine change of the modulus of elasticity is treated, furnishing the solution for arbitrary variation in the form of a Fourier's expansion. Finite element analysis is subsequently performed for investigating the scope of validity of the analytical solution. The results for a set of finite changes of the elastic modulus are compared with the analytical predictions, and a remarkably wide range of validity is demonstrated. New functions, suitable for non-homogeneous material description, are introduced to approach the case of non-constant Poisson's ratio. The properties and possible applications of these functions are examined.Godkänd; 1999; 20070320 (ysko)
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Hauber, Brett Kenneth. "Fatigue Crack Propagation in Functionally Graded Materials." University of Dayton / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1259881312.
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Garbin, F., F. Garbin, A. Levano, and R. Arciniega. "Bending Analysis of Nonlocal Functionally Graded Beams." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/651836.
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In this paper, we study the nonlocal linear bending behavior of functionally graded beams subjected to distributed loads. A finite element formulation for an improved first-order shear deformation theory for beams with five independent variables is proposed. The formulation takes into consideration 3D constitutive equations. Eringen's nonlocal differential model is used to rewrite the nonlocal stress resultants in terms of displacements. The finite element formulation is derived by means of the principle of virtual work. High-order nodal-spectral interpolation functions were utilized to approximate the field variables, which minimizes the locking problem. Numerical results and comparisons of the present formulation with those found in the literature for typical benchmark problems involving nonlocal beams are found to be satisfactory and show the validity of the developed finite element model.
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Richard, Flesner Reuben. "Modeling of Solid Oxide Fuel Cell functionally graded electrodes and a feasibility study of fabrication techniques for functionally graded electrodes." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1473204.
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Dietrich, Jan [Verfasser]. "Functional adhesives and functionally graded adhesives in fiber metal laminates / Jan Dietrich." Paderborn : Universitätsbibliothek, 2020. http://d-nb.info/1217325867/34.
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Yilmaz, Suphi. "Buckling Driven Delamination Of Orthotropic Functionally Graded Materials." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607836/index.pdf.
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In today's technology severe working conditions increase demands on structural materials. A class of materials which are developed to meet these increased demands is Functionally Graded Materials (FGMs). These are inhomogeneous structural materials which are able to withstand large temperature gradients and corrosive environment. Application areas of FGMs are in aerospace industry, nuclear reactors, chemical plants and turbine systems. FGMs have gradual compositional variation from metal to ceramic which give them mechanical strength, toughness and heat resistance. However under high temperature gradients, cracking problems may arise due to thermal stresses. In layered structures the final stage of failure may be delamination due to crack extension. The objective of this study is to model a particular type of crack problem in a layered structure consisting of a substrate, a bond coat and an orthotropic FGM coating. There is an internal crack in the orthotropic layer and it is perpendicular to material gradation of coating. The position of the crack inside the coating is kept as a variable. The steady-state temperature distribution between the substrate and the coating causes a buckled shape along crack face. The critical temperature change, temperature distribution, mixed mode stress intensity values and energy release rates are calculated by using Displacement Correlation Technique. Results of this study present the effects of geometric parameters such as crack length, crack position, etc as well as the effects of the type of gradation on buckling behavior and mixed mode stress intensity factors.
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Hart, Nigel T. "Functionally graded interfaces for solid oxide fuel cells :." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445940.
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Luo, Wenjin. "Thermal Shock Fracture Behaviors of Functionally Graded Ceramics." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/LuoW2006.pdf.
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SOARES, ALEXANDRE ANDRADE BRANDAO. "NONLINEAR FREE VIBRATIONS OF FUNCTIONALLY GRADED CYLINDRICAL SHELLS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35622@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Cascas cilíndricas são usadas em muitas aplicações de engenharia e, devido a sua forma e capacidade de transporte de carga, são bastante usadas na indústria aeroespacial e em estruturas civis. Elas minimizam a quantidade de material do qual são fabricadas, tornando-se assim estruturas muito leves e esbeltas. Em décadas recentes tem se procurado criar novos materiais que conjuguem múltiplas propriedades como maior resistência, melhor proteção térmica, proteção contra corrosão e adequado nível de amortecimento, dentre outras. Uma classe de materiais que podem atender simultaneamente várias destas exigências é o chamado material com gradação funcional, onde as propriedades do material variam de forma contínua em uma ou mais direções. Materiais com gradação funcional são particularmente indicados para a construção de cascas. Como a maioria destas estruturas estão sujeitas a cargas dinâmicas, torna-se importante o estudo do comportamento dinâmico de cascas fabricadas com materiais com gradação funcional. O objetivo deste trabalho é estudar as vibrações não lineares de cascas cilíndricas esbeltas com gradação funcional. Para isto utiliza-se a teoria não linear de cascas de Sanders, considerada uma das teorias mais precisas para a análise de cascas esbeltas. Inicialmente, derivam-se as equações de movimento considerando um estado de tensões iniciais. Usando as equações linearizadas, obtêm-se às frequências naturais e as cargas críticas, sendo estes resultados comparados favoravelmente com resultados encontrados na literatura para materiais homogêneos e com gradação funcional. A seguir, usando uma expansão modal que atende as condições de contorno e continuidade, além de expressar os acoplamentos modais característicos de cascas cilíndricas no regime não linear, as equações de movimento são discretizadas usando-se o método de Galerkin. As equações algébricas resultantes são resolvidas pelo método de Newton-Raphson, sendo assim obtida a relação não linear frequência-amplitude. Finalmente, realiza-se uma análise paramétrica para estudar a influência da geometria da casca, da gradação do material funcional e dos modos de vibração no grau e tipo de não linearidade da casca cilíndrica, sendo esta a principal contribuição deste trabalho de pesquisa.
Cylindrical shells are used in many engineering applications and, due to its shape and load carrying capacity, are frequently used in aerospace and civil structures. They minimize the amount of material from which they are manufactured, thus making it a very lightweight and slender structure. In recent decades, there has been a search for new materials that combine multiple properties such as increased strength, better thermal protection, corrosion protection and appropriate damping level, among others. A material that can meet several of these requirements simultaneously is the so called functionally graded material, where the material properties vary continuously in one or more directions. Functionally graded materials are particularly suitable for the construction of shells. As most of these structures are subjected to dynamic loads, it is important to study the dynamic behavior of shells made of functionally graded materials. The objective of this work is to study the nonlinear vibrations of slender functionally graded cylindrical shells. For this, the Sanders non-linear shell theory, which is considered one of the most precise theories for the analysis of slender shells, is adopted. Initially, the equations of motion are derived considering an initial stress state. Using the linearized equations of motion, the natural frequencies and critical loads are obtained. These results compare favorably with results reported in the literature for homogeneous and functionally graded shells. Then, using a modal expansion that satisfies the boundary and continuity conditions and expresses the modal couplings characteristic of cylindrical shells in the nonlinear regime, the equations of motion are discretized using the Galerkin method. The resulting algebraic equations are solved by the Newton-Raphson method, thus obtaining the nonlinear frequency-amplitude relation. Finally, a parametric analysis is conducted to study the influence of the geometry of the shell, the gradient of the functional material and vibration modes on the degree and type of nonlinearity of the cylindrical shell, which is the main contribution of this research work.
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Jackson, Todd Robert. "Analysis of functionally graded material object representation methods." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9032.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.Includes bibliographical references (leaves 218-224).
Solid Freeform Fabrication (SFF) processes have demonstrated the ability to produce parts with locally controlled composition. To exploit this potential, methods to represent and exchange parts with varying local composition need to be proposed and evaluated. In modeling such parts efficiently, any such method should provide a concise and accurate description of all of the relevant information about the part with minimal cost in terms of storage. To address these issues, several approaches to modeling Functionally Graded Material (FGM) objects are evaluated based on their memory requirements. Through this research, an information pathway for processing FGM objects based on image processing is proposed. This pathway establishes a clear separation between design of FGM objects, their processing, and their fabrication. Similar to how an image is represented by a continuous vector valued function of the intensity of the primary colors over a two-dimensional space, an FGM object is represented by a vector valued function spanning a Material Space, defined over the three dimensional Build Space. Therefore, the Model Space for FGM objects consists of a Build Space and a Material Space. The task of modeling and designing an FGM object, therefore, is simply to accurately represent the function m(x) where x E Build Space. Data structures for representing FGM objects are then described and analyzed, including a voxel based structure, finite element method, and the extension of the Radial-Edge and Cell-Tuple-Graph data structures mains in order to represent spatially varying properties. All of the methods are capable of defining the function m(x) but each does so in a different way. Along with introducing each data structure, the storage cost for each is derived in terms of the number of instances of each of its fundamental classes required to represent an object. In order to determine the optimal data structure to model FGM objects, the storage cost associated with each data structure for representing several hypothetical models is calculated. Although these models are simple in nature, their curved geometries and regions of both piece-wise constant and non-linearly graded compositions reflect the features expected to be found in real applications. In each case, the generalized cellular methods are found to be optimal, accurately representing the intended design.
by Todd Robert Jackson.
Ph.D.
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Sarikaya, Duygu. "Mixed-mode Fracture Analysis Of Orthotropic Functionally Graded Materials." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606451/index.pdf.
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Functionally graded materials processed by the thermal spray techniques such as electron beam physical vapor deposition and plasma spray forming are known to have an orthotropic structure with reduced mechanical properties. Debonding related failures in these types of material systems occur due to embedded cracks that are perpendicular to the direction of the material property gradation. These cracks are inherently under mixed-mode loading and fracture analysis requires the extraction of the modes I and II stress intensity factors. The present study aims at developing semi-analytical techniques to study embedded crack problems in graded orthotropic media under various boundary conditions. The cracks are assumed to be aligned parallel to one of the principal axes of orthotropy. The problems are formulated using the averaged constants of plane orthotropic elasticity and reduced to two coupled integral equations with Cauchy type dominant singularities. The equations are solved numerically by adopting an expansion - collocation technique. The main results of
the analyses are the mixed mode stress intensity factors and the energy release rate as functions of the material nonhomogeneity and orthotropy parameters. The effects of
the boundary conditions on the mentioned fracture parameters are also duly discussed.
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Sabuncuoglu, Baris. "Fatigue Crack Growth Analysis Models For Functionally Graded Materials." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607024/index.pdf.
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The objective of this study is to develop crack growth analysis methods for functionally graded materials under mode I cyclic loading by using finite element technique. The study starts with the analysis of test specimens which are given in
ASTM standard E399. The material properties of specimens are assumed to be changing along the thickness direction according to a presumed variation function used for the modeling of functionally graded materials. The results of the study reveal the influence of different material variation functions on the crack growth
behavior.
In the second part, the growth of an elliptical crack which is a common case in engineering applications is analyzed. First, mode I cycling loading is applied perpendicular to the crack plane and crack growth profiles for a certain number of cycles are obtained for homogeneous materials. Then, the code is extended for the analysis functionally graded materials. The material properties are assumed to vary as an exponential function along the major or minor axis direction of the crack. The results can be used to examine the crack profile and material constants&rsquoinfluence for a certain number of cyclic loading.
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Imery, Buiza Jesus Alberto. "Fracture behaviour of 2124 A1-SiC functionally graded materials." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321715.
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Trinh, Luan Cong. "Behaviours of functionally graded sandwich micro-beams and plates." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36216/.
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Functionally graded materials (FGMs) are a novel class of materials having unique characteristics formed of two or more constituent phases with a continuously variable composition. The introduction of these materials to the sandwich structures creates more potentials to the structural applications with the ability of tailoring the material properties as well as the possibility of avoiding the delamination and stress concentration in conventional sandwich structures. With the rapid development of technology, it is now common to use FGMs in micro/nanoelectromechanical systems, e.g. thin films, sensors, actuators and other devices. At these scales, the use of experimentation to understand the structural behaviours is difficult and highly time-consuming, whilst the molecular modelling is computationally very expensive for the scales that are popular to structural engineers. Therefore, higher-order continuum theories, which were developed from the classical continua, become very popular in modelling micro/nano-scale structures. Based on one of these higher-order continuum theories namely the modified couple stress theory, this thesis aims to develop the analytical methods, i.e. Navier and state space based solutions, to analyse the static, free vibration and buckling behaviours of FG and FG-sandwich beams and plates. The governing equations and appropriate boundary conditions are developed for these structural behaviours of beams and plates at both micro and macro- scales using the variational principle. Numerical results are computed using MATLAB and verified with the published results to demonstrate the accuracy and efficiency of the developed theoretical formulation. The numerical applications include: · the free vibration and buckling behaviours of FG and FG sandwich macrobeams under arbitrary boundary conditions and mechanical/thermal loads, · the static, free vibration and buckling behaviours of simply supported FG microbeams, and the free vibration behaviour of bidirectional FG microbeams under arbitrary boundary conditions, · the static, free vibration and buckling behaviours of simply supported FG-sandwich microplates under mechanical/thermal loads, · the static, free vibration and buckling behaviours of FG-sandwich microplates with two opposite simply supported edges and various boundary conditions for other edges. The outcomes from this thesis emphasize the need of including couple stress in analyzing the structural behaviours of FG beams and plates at microscales. Some of them are presented at the first time and can be used as the benchmark results for numerical methods. These analytical methods can also be combined with other strong form methods to analyse various types of complex structures.
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Woodward, Ben. "3D modelling of sandwich panels with functionally graded core." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=211061.
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Sandwich panels are a type of structural panel, typically comprising two thin layers of high strength and stiffness known as face sheets which separate a thicker lightweight core of lower strength, stiffness and density. When combined, these layers offer excellent flexural strength to weight ratio without compromising on stiffness. Sandwich panels are utilised in a wide range of industries and applications from aerospace to construction. Due to mismatch of properties between face sheets and core, stress concentrations can occur at the interfaces, often causing delamination. One solution is inclusion of a functionally graded core; a core with properties which vary gradually from the face sheets to the centre, eliminating any abrupt changes in properties. Current research presents newly developed three dimensional analytical and numerical solutions used to gain further understanding of the introduction of a functionally graded core. A three dimensional elasticity solution for an isotropic sandwich panel with stiffness of the core graded in the thickness direction was developed, allowing for comparison of panels with functionally graded and homogenous cores to be completed. It was discovered that inclusion of the graded core removes the discontinuity in stresses at the interfaces and decreases both in- and out-of plane displacements throughout the panel. Since many real functionally graded materials do not exhibit isotropic characteristics, a three dimensional elasticity solution was thereafter developed for a sandwich panel with transversely isotropic core. The effects of individual engineering constants on panel performance were then studied and it was noted that the effects of shear deformation are obvious in thinner panels and those with low transverse shear modulus. A finite element model in ABAQUS was also developed, allowing geometry, loading and boundary conditions to be easily varied. To capture the continuously varying properties of the graded core, user defined graded finite elements were implemented.
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Awrejcewicz, Jan, Lidiya Kurpa, and T. Shmatko. "Vibration of functionally graded shallow shells with complex shape." Thesis, Department of Automation, Biomechanics and Mechatronics, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37081.
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The method for studying the geometrically nonlinear vibrations of functionally graded shallow shells with a complex planform is proposed. Сomposite shallow shells made from a mixture of ceramic and metal are considered. In order to take into account varying of the volume fraction of ceramic the power law is accepted. Formulation of the problem is carried out using the refined geometrically nonlinear theory of shallow shells of the first order (Timoshenko’s type). The R-functions theory, variational Ritz’s method, procedure by Bubnov Galerkin and Runge-Kytta method are used in the developed approach. A distinctive feature of the proposed approach is the method of reducing the initial nonlinear system of equations of motion for partial derivatives to a nonlinear system of ordinary differential equations. According to the developed approach first it is necessary to solve linear vibration problem. Further to solve elasticity problems for inhomogeneous differential equations with right hand side, containing eigen functions. Obtained solutions of these problems are applied for representation of unknown functions of the nonlinear problem. Application of the theory of R-functions on every step allows us to extend the proposed approach to the shell with arbitrary shape of plan and different kinds of boundary condition. The proposed method is validated by investigation of test problems for shallow shells with rectangular and elliptical planform and applied to new vibration problems for shallow shells with complex planform.
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Pelletier, Jacob Leo. "Thermoelastic Analysis and Optimization of Functionally Graded Plates and Shells." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/PelletierJL2005.pdf.
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Wang, Xuan. "Synthesis of functionally graded materials via electrophoretic deposition and sintering /." Diss., Connect to a 24 p. preview or request complete full text in PDF formate. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3208812.
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Kosker, Sadik. "Three Dimensional Mixed Mode Fracture Analysis Of Functionally Graded Materials." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608795/index.pdf.
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The main objective of this study is to model and analyze a three dimensional inclined semi-elliptic surface crack in a Functionally Graded Material (FGM) coating bonded to a homogeneous substrate with a bond coat. The parametric analyses on FGMs are based upon zirconia-yttria (ZrO2-8wt%-Y2O3) FGM coating bonded to a substrate made of a nickel-based superalloy. It is assumed that there is a nickel-chromium–
aluminum&
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zirconium (NiCrAlY) bond coat between the FGM coating and substrate. Metal-rich, linear variation, ceramic-rich and homogeneous ceramic FGM coating types are considered in the analyses. The inclined semi-elliptic surface crack problem in the FGM coating-bond coat-substrate system is analyzed under transient thermal loading. This problem is modeled and analyzed by utilizing three dimensional finite elements. Strain singularity around the crack front is simulated using collapsed 20 &
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node quarter &
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point brick elements. Three &
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dimensional displacement correlation technique is utilized to extract the mixed mode stress intensity factors around the crack front for different inclination angles of the semi-elliptic surface crack. The energy release rates around the crack front are also calculated by using the evaluated mixed mode stress intensity factors. The results obtained in this study are the peak values of mixed mode stress intensity factors and energy release rates around the crack front for various inclination angles of the semi-elliptic surface crack embedded in the FGM coating of the composite structure subjected to transient thermal loading.
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Oyekoya, Oyedele. "Structural integrity of engineering components made of functionally graded materials." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3802.
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Functionally graded materials (FGM) are composite materials with microstructure gradation optimized for the functioning of engineering components. For the case of fibrous composites, the fibre density is varied spatially, leading to variable material properties tailored to specific optimization requirements. There is an increasing demand for the use of such intelligent materials in space and aircraft industries. The current preferred methods to study engineering components made of FGM are mainly modelling particularly those that are finite element (FE) based as experimental methods have not yet sufficiently matured. Hence this thesis reports the development of a new Mindlin-type element and new Reissner-type element for the FE modelling of functionally graded composite (FGC) structures subjected to various loadings such as tensile loading, in-plane bending and out-of-plane bending, buckling and free vibration. The Mindlin-type element formulation is based on averaging of transverse shear distribution over plate thickness using Lagrangian interpolation. Two types of Mindlintype element were developed in this report. The properties of the first Mindlin-type element (i.e. Average Mindlin-type element) are computed by using an average fibre distribution technique which averages the macro-mechanical properties over each element. The properties of the second Mindlin-type element (i.e. Smooth Mindlin-type element) are computed by using a smooth fibre distribution technique, which directly uses the macro-mechanical properties at Gaussian quadrature points of each element. The Reissner-type element formulation is based on parabolic transverse shear distribution over plate thickness using Lagrangian and Hermitian interpolation. Two types of Reissner-type element were developed in this report, which include the Average and Smooth Reissner-type elements. There were two types of non-linearity considered in the modelling of the composite structures, which include finite strain and material degradation. The composite structures considered in this paper are functionally graded in a single direction only, but the FE code developed is capable of analysing composite structures with multidirectional functional gradation. This study was able to show that the structural integrity enhancement and strength maximisation of composite structures are achievable through functional gradation of material properties over the composite structures.
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Pogson, Simon Richard. "Fabrication of functionally graded structures by direct metal laser remelting." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494170.
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Investigations have been conducted into the production of Functionally Graded Structures (FGS) with varying composition and porosity using Direct Metal Laser Remelting (DMLR), a Rapid Prototyping (RP) technology. Following a series of experiments on a number of metal systems and analyses conducted using a series of metallographic and spectrographic techniques (SEM-EDS, XRD), it has been possible to assess the viability of a processing system to produce tailored structures.
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Gleim, Tobias [Verfasser]. "Simulation of Manufacturing Sequences of Functionally Graded Structures / Tobias Gleim." Kassel : Kassel University Press, 2016. http://d-nb.info/1127536443/34.
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ALBINO, JUAN CARLOS ROMERO. "FUNCTIONALLY GRADED MATERIALS ON THE DYNAMIC BEHAVIOR OF FLEXIBLE RISERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19447@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONeste trabalho um novo elemento de viga co-rotacionado é apresentado para a análise não-linear geométrica tridimensional, estática e dinâmica, de linhas marítimas de Materiais com Gradação Funcional (MGF). Assume-se que o módulo de elasticidade e a massa específica do material da viga variam ao longo da espessura da seção transversal tubular de acordo com uma lei de potência. Na discretização espacial das equações de equilíbrio, a linha marítima é representada por um elemento de viga de dois nós, com base nas hipóteses do modelo para vigas de Euler-Bernoulli, em que polinômios cúbicos de Hermite são utilizados na interpolação dos deslocamentos nodais e a cinemática do movimento é descrita através de grandezas referidas a um sistema coordenado local co-rotacionado. Consideram-se não linearidades geométricas envolvendo grandes deslocamentos e rotações, mas com pequenas deformações. Nas equações de movimento da linha marítima, são consideradas as seguintes influencias: do peso próprio, do empuxo, dos carregamentos hidrodinâmicos (devidos às ações de ondas, correntes e forças de massa adicional), dos deslocamentos prescritos (junto à fixação da embarcação), da ação de flutuadores e das forças de interação solo-estrutura. A integração temporal das equações de equilíbrio é realizada utilizando-se o algoritmo de discretização HHT (Hilbert-Hughes-Taylor) e a solução numérica obtida com a técnica iterativa de Newton Raphson. A metodologia numérica foi implementada e diversos exemplos são apresentados e discutidos enfatizando-se as diferenças de comportamento estrutural entre os modelos de viga com MGF e com material homogêneo. Resultados referentes a situações práticas da engenharia offshore são também tratados nos exemplos.
This work presents a new co-rotational beam element formulation to model the geometric three-dimensional static and dynamic nonlinear analysis of risers of Functionally Graded Materials (FGM). The material modulus of elasticity and density of the beam are assumed to vary through the pipe cross-section thickness following a power law function. In the spatial discretization of the riser equilibrium equations, a two node beam element based on Euler-Bernoulli theory is considered, with cubic Hermitian interpolation functions used for nodal displacement interpolations and element kinematics, all referred to a co-rotation coordinate system attached to the element local frame. In the element model, geometric non-linear effects are considered, involving large displacements and rotations but small strains. The motion of the riser results from the following applied forces: self weight, buoyancy, hydrodynamic (due to maritime waves, currents and added mass inertia), prescribed displacements (at the floating platform), action of floaters and seabed-structure interactions. Step-by-step time integration of the equilibrium equations is performed with HHT (Hilbert-Hughes- Taylor) algorithm and the numerical solution is obtained using the Newton- Raphson iterative technique. The methodology has been implemented and various sample results presented, that highlight the behavior of functionally graded material beams as compared to homogeneous beams. Applications related to practical offshore engineering situations are also considered.
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Liu, Hongye 1970. "Algorithms for design and interrogation of functionally graded material solids." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9044.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (leaves 109-112).
A Functionally Gradient Material (FGM) part is a 3D solid object that has varied local material composition that is defined by a specifically designed function. Recently, research has been performed at MIT in order to exploit the potential of creating FGM parts using a modern fabrication process, 3D Printing, that has the capability of controlling composition to the length scale of 100 [mu]m. As part of the project of design automation of FGM parts, this thesis focuses on the issue of the development of efficient algorithms for design and composition interrogation. Starting with a finite element based 3D model, the design tool based on the distance function from the surface of the part and the design tool allowing the user to design within a .STL file require enhanced efficiency and so does the interrogation of the part. The approach for improving efficiency includes preprocessing the model with bucket sorting, digital distance transform of the buckets and an efficient point classification algorithm. Based on this approach, an efficient algorithm for distance function computation is developed for the design of FGM through distance to the surface of the part or distance to a .STL surface boundary. Also an efficient algorithm for composition evaluation at a point, along a ray or on a plane is developed. The theoretical time complexities of the developed algorithms are analyzed and experimental numerical results are provided.
by Hongye Liu.
S.M.
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DESHMUKH, PUSHKARAJ M. "MODELING ERROR ESTIMATION AND ADAPTIVE MODELING OF FUNCTIONALLY GRADED MATERIALS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1096036755.
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SURANA, RAJESH R. "HIGH STRAIN FUNCTIONALLY GRADED BARIUM TITANATE AND ITS MATHEMATICAL CHARACTERIZATION." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1096650232.
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Bhatkar, Omkar S. "Facile Fabrication of Functionally Graded Graphene Films for Transient Electronics." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1544623828859207.
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Shah, Kamran. "Laser direct metal deposition of dissimilar and functionally graded alloys." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/laser-direct-metal-deposition-of-dissimilar-and-functionally-graded-alloys(baa5f8fd-cead-4047-afbf-860844b501d8).html.
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The challenges in the deposition of dissimilar materials are mainly related to the large differences in the physical and chemical properties of the deposited and substrate materials. These differences readily cause residual stresses and intermetallic phases. This has led to the development of functionally graded materials which exhibit spatial variation in composition. Laser direct metal deposition due to its flexibility, it offers wide variety of dissimilar and functionally graded materials deposition. Despite considerable advances in process optimization, there is a rather limited understanding of the role of metallurgical factors in the laser deposition of dissimilar and functionally graded alloys. The aim of this work is to understand and explain mechanisms occurring in diode laser deposition of dissimilar materials and functionally graded materials. The first part of this work addressed diode laser deposition of Inconel 718 nickel alloy to Ti-6Al-4V titanium alloy. Here, the effect of laser pulse parameters and powder mass flow rates on the stress formation and cracking has evaluated by experiment and numerical techniques. Results showed that the clad thickness was an important factor affecting the cracking behaviour. In the second part of this study, an image analysis technique has been developed to measure the surface disturbance and the melt pool cross section size during laser direct metal deposition of Inconel 718 on a Ti-6Al-4V thin wall. It was noted that under tested conditions the overall melt pool area increased with the increase in powder flow rate; the powder carrier gas flow rates also seemed to play important roles in determining the melt pool size. In the third part of this study, a parametric study on the development of Inconel 718 and Stainless steel 316L continuously graded structure has been carried out. Results suggested that microstructure and other mechanical properties can be selectively controlled across the deposited wall. The results presented in this dissertation can be used as a metallurgical basis for further development of dissimilar and functionally graded manufacturing using LDMD technique, guiding future manufacturing engineers to produce structurally sound and microstructurally desirable laser deposited samples.
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Pines, Michael Louis. "Pressureless sintering of powder processed functionally graded metal-ceramic plates." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1999.
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Thesis (M.S.) -- University of Maryland, College Park, 2004.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Deshmukh, Pushkaraj M. "Modelling error estimation and adaptive modelling of functionally graded materials." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1096036755.
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Oyekoya, Oyedele O. "Structural integrity of engineering components made of functionally graded materials." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3802.
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Functionally graded materials (FGM) are composite materials with microstructure
gradation optimized for the functioning of engineering components. For the case of
fibrous composites, the fibre density is varied spatially, leading to variable material
properties tailored to specific optimization requirements. There is an increasing demand
for the use of such intelligent materials in space and aircraft industries. The current
preferred methods to study engineering components made of FGM are mainly
modelling particularly those that are finite element (FE) based as experimental methods
have not yet sufficiently matured. Hence this thesis reports the development of a new
Mindlin-type element and new Reissner-type element for the FE modelling of
functionally graded composite (FGC) structures subjected to various loadings such as
tensile loading, in-plane bending and out-of-plane bending, buckling and free vibration.
The Mindlin-type element formulation is based on averaging of transverse shear
distribution over plate thickness using Lagrangian interpolation. Two types of Mindlintype
element were developed in this report. The properties of the first Mindlin-type
element (i.e. Average Mindlin-type element) are computed by using an average fibre
distribution technique which averages the macro-mechanical properties over each
element. The properties of the second Mindlin-type element (i.e. Smooth Mindlin-type
element) are computed by using a smooth fibre distribution technique, which directly
uses the macro-mechanical properties at Gaussian quadrature points of each element.
The Reissner-type element formulation is based on parabolic transverse shear
distribution over plate thickness using Lagrangian and Hermitian interpolation. Two
types of Reissner-type element were developed in this report, which include the
Average and Smooth Reissner-type elements.
There were two types of non-linearity considered in the modelling of the composite
structures, which include finite strain and material degradation. The composite
structures considered in this paper are functionally graded in a single direction only, but
the FE code developed is capable of analysing composite structures with multidirectional
functional gradation. This study was able to show that the structural
integrity enhancement and strength maximisation of composite structures are achievable
through functional gradation of material properties over the composite structures.
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Okubo, Hitoshi, Hideki Shumiya, Masahiro Ito, and Katsumi Kato. "Insulation Performance of Permittivity Graded FGM (Functionally Graded Materials) in SF6 Gas under Lightning Impulse Conditions." IEEE, 2006. http://hdl.handle.net/2237/9496.
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Goupee, Andrew. "Methodology for the Thermomechanical Simulation and Optimization of Functionally Graded Materials." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/GoupeeA2005.pdf.
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Pratapa, Suminar. "Synthesis and character of a functionally-graded aluminium titanate/zirconia-alumina composite." Thesis, Curtin University, 1997. http://hdl.handle.net/20.500.11937/988.
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A functionally-graded Al(subscript)2TiO(subscript)5/ZrO(subscript)2-Al(subscript)2O(subscript)3 (AT/zirconia-alumina) composite has been successfully synthesized by an infiltration process involving an alpha-Al(subscript)2O(subscript)3-ZrO(subscript)2 (90:10 by weight) green body and a solution containing titanium chloride. The mass gain after infiltration has been used to estimate the amount of new phase introduced into the system. The phase composition character of the functionally-graded material (FGM) has been determined by x-ray diffraction. The Rietveld "whole pattern" refinement method was applied to diffraction patterns of the sample which were collected from the surface and at several depths which were made by polishing away the material. Absolute weight fraction determination using the Rietveld external standard method showed that the concentration of AT reduces linearly from the surface to the core. In contrast, the alpha-alumina content increases with depth in a complementary manner. Low level amorphous phase was also observed. Other functionally-graded microstructural profiles examined were x-ray characteristic line intensity of Ti, Ti dot-mapping, and alpha-alumina grain size. The FGM also exhibits graded character in both thermal and mechanical properties, i.e. thermal expansion, microhardness, and Young's modulus. The thermal expansion coefficient (TEC) of the FGM increased with polishing-depth and approached that of the zirconia-alumina reference sample at a depth of 0.5 mm.Relatively lower thermal expansion and softer surface layer in comparison to those of the core (TEC value of 5.9 x 10(subscript)-6 degrees celsius(subscript)-1 and microhardness of 6 GPa compared to 7.4 x 10(subscript)-6 degrees celsius(subscript)-1 and 12 GPa, respectively) render possibilities to implement the material to which thermal shock resistance surface but hard core, such as a metal melting crucible, are required. Load-dependent microhardness was obviously observed on the surface of the material but only slight dependence was observed in the core. This observation indicated that the material exhibit "quasi-ductile" surface but brittle core. In comparison to the reference specimen, the FGM displayed damage-tolerance and remarkable machinability.
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Gao, Xiong. "Two-dimensional exact analysis of functionally graded piezoelectric cantilevers under electric and mechanical loadings." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3950671.
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Janković, Ilić Dragana. "Self formed Cu-W functionally graded material created via powder segregation." Aachen Shaker, 2008. http://d-nb.info/999932683/34.
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Bell, Bryan Frederick Jr. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7962.
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Coco, Suzanne Kemp. "A mechanical and histological study of functionally graded hydroxyapatite implant coatings." View the abstract Download the full-text PDF version, 2008. http://etd.utmem.edu/ABSTRACTS/2008-009-Coco-index.html.
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Thesis (M.S.)--University of Tennessee Health Science Center, 2008.Title from title page screen (viewed on June 10, 2008). Research advisor: Joo Leng Ong, Ph.D. Document formatted into pages (vi, 34 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 31-34).
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Janković, Ilić Dragana. "Self formed Cu-W functionally graded material created via powder segregation." Aachen Shaker, 2007. http://d-nb.info/987900730/04.
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Wu, Kangjian [Verfasser]. "Process development for ZrO2-ZrSiO4/NiCr functionally graded materials / Kangjian Wu." Aachen : Shaker, 2013. http://d-nb.info/1050344340/34.
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Caraballo, Simon. "Thermo-Mechanical Beam Element for Analyzing Stresses in Functionally Graded Materials." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3024.
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Modeling at the structural scale most often requires the use of beam and shell elements. This simplification reduces modeling complexity and computation requirements but sacrifices the accuracy of through-the-thickness information. Several studies have reported various design approaches for analyzing functionally graded material structures. One of these studies proposed a two-node beam element for functionally graded materials (FGMs) based on first order shear deformable (FOSD) theory. The derivation of governing equations included spatial temperature variation. However, only the constant temperature case was carried through in the element formulation. This investigation explore the effects of spatial temperature variation in the axial and through-the-thickness direction of this proposed element and present a new standard three-node beam finite element modified for structure constructed of FGMs. Also, the influence of the temperature dependency of the thermo-elastic material properties on the thermal stresses distribution was studied. In addition, variations in the layer thicknesses within multilayer beam models were studied to determine the effect on stresses and factor of safety. Finally, based on the specific factor of safety, which combines together the strength and mass of the beam, the best layer thicknesses for the beam models were established.
The key contributions expected from this research are:
1. development and implementation of a three-node beam element as a finite element code into the commercial computational tool MATLAB® to analyze thermo-mechanical stresses in structures constructed of functionally graded materials;
2. a strategy to simulate different load cases in structures constructed of functionally graded materials;
3. an analysis of the influence of the FGM interlayer thickness on the factor of safety/specific gravity ratio in structures constructed of functionally graded materials under thermo-mechanical loads;
4. and an analysis/comparison of the advantages/benefits of using structures constructed of functionally graded materials with respect to those constructed with homogenous materials.
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(UPC), Universidad Peruana de Ciencias Aplicadas, J. Yarasca, J. L. Mantari, and R. A. Arciniega. "Hermite–Lagrangian finite element formulation to study functionally graded sandwich beams." Elsevier B.V, 2016. http://hdl.handle.net/10757/607194.
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This paper presents a static analysis of functionally graded single and sandwich beams by using an efficient 7DOFs quasi-3D hybrid type theory. The governing equations are derived by employing the principle of virtual works in a weak form and solved by means of the Finite Element Method (FEM). A C1 cubic Hermite interpolation is used for the vertical deflection variables while C0 linear interpolation is employed for the other kinematics variables. Convergence rates are studied in order to validate the finite element technique. Numerical results of the present formulation are compared with analytical and FEM solutions available in the literature.Revisión por pares
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Vallejos, Augusto, Shammely Ayala, and Roman Arciniega. "Improved First Order Formulation for Buckling Analysis of Functionally Graded Beams." Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656419.
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El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.In this research, an improved first order formulation is presented to study the critical buckling load in functionally graded beams. The formulation has five independent variables in comparison with the Timoshenko theory that has three. The Trefftz criterion is utilized with incremental and fundamental states to define the stability analysis. Virtual work statements are derived for the finite element model where the field variables are interpolated by Lagrange polynomials. The numerical results are compared and verified with other formulations found in literature. Parametric studies are also carried out for buckling behavior due to different slenderness ratios, power-law indices and boundary conditions. Applications of the model to functionally graded materials show the validity of the present approach.
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Lee, Seon-Jae. "Micromechanical model for predicting the fracture toughess of functionally graded foams." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013705.
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Lyon, Mark Edward. "Incorporating Functionally Graded Materials and Precipitation Hardening into Microstructure Sensitive Design." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd260.pdf.
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Bell, Bryan Frederick. "Functionally graded, multilayer diamondlike carbon-hydroxyapatite nanocomposite coatings for orthopedic implants." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-06072004-131058/unrestricted/bell%5Fbryan%5Ff%5F200405%5Fms.pdf.
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