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1
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.
Testo completoAbstract (sommario):
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.
2
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.
Testo completoAbstract (sommario):
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.
3
Pratapa, Suminar. "Synthesis and character of a functionally-graded aluminium titanate/zirconia-alumina composite." Curtin University of Technology, Department of Applied Physics, 1997. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14696.
Testo completoAbstract (sommario):
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.<br>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.
4
Arman, Eyup Erhan. "Jk-integral Formulation And Implementation For Thermally Loaded Orthotropic Functionally Graded Materials." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610136/index.pdf.
Testo completoAbstract (sommario):
The main aim of this study is to utilize a Jk-integral based computational method in order to calculate crack tip parameters for orthotropic functionally graded materials (FGMs). The crack is subjected to mixed mode thermal loading. Mixed mode thermal fracture analysis requires the calculation of mode-I and mode-II stress intensity factors (KI ,KII ). In addition to stress intensity factors, energy release rate and T-stress are calculated by means of Jk-integral. Jk-integral is defined as a line integral over a vanishingly small curve. Since it is difficult to deal with a line integral on a vanishing curve , Jk-integral is converted to a domain independent form containing area and line integrals by the help of plane thermoelasticity constitutive relations. Steady-state temperature distribution profiles in FGMs and the components of the Jk-integral are computed by means of the finite element method.
In both thermal and structural analyses, finite element models that possess graded isoparametric elements are created in the general purpose finite element analysis software ANSYS. In the formulation of Jk-integral, all required engineering material properties are assumed to possess continuous spatial variations through the functionally graded medium. The numerical results are compared to the results obtained from Displacement Correlation Technique (DCT). The domain independence of Jk-integral is also demonstrated. The results obtained in this study show the effects of crack location and material property gradation profiles on stress intensity factors, energy release rate and T-stress.
5
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.
Testo completo
6
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.
Testo completo
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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.
Testo completoAbstract (sommario):
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&<br>#8211<br>aluminum&<br>#8211<br>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 &<br>#8211<br>node quarter &<br>#8211<br>point brick elements. Three &<br>#8211<br>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.
8
Hosseinzadeh, Delandar Arash. "Finite element analysis of thermally induced residual stresses in functionally graded materials." Thesis, KTH, Materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92519.
Testo completoAbstract (sommario):
Functionally graded materials (FGMs) are advanced materials and their main characteristic is microstructure and composition variation over the volume of the specimen. This variation of the composition results in changing of material properties in the component. In FGMs usually there are two different types of powder materials such as metal and ceramic powders which are mixed to build up the graded region. These grade layers are placed between the metal and ceramic layers and by this approach a smooth and gradual transient from metal to ceramic can be achieved.Sintering is the main technique to manufacture these types of materials. During the sintering process, cooling of the specimen from sintering temperature to room temperature results in generation of thermal residual stresses within the material. These thermal stresses may cause crack propagation and failure of the material.Distribution analysis of these thermally induced stresses within the material has been carried out in this thesis work. Finite element package ABAQUS has been used in order to simulate the distribution of the thermal residual stresses in the materials. In order to achieve the optimal design for different geometries the parametric study also has been performed. For example influence of number of layers, mixing ratio and porosity has been investigated.Based on the finite element results for cylindrical and cuboid models, non-linear composition variation for both geometries has no improving effect in terms of induced thermal residual stresses. Porous material shows less thermal stress than non-porous material. As the amount of porosity for individual layer was considered in simulation process, this approach resulted in decreasing of thermal stresses within the material. Moreover, non-uniform thickness of graded layers was not beneficial for stress reduction. This variation of thickness results in increasing of thermal residual stresses within the material.
9
Mellachervu, Krishnaveni. "Study of the honeycomb structures and functionally graded materials using the BEM and FEM." Cincinnati, Ohio : University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1206460053.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Cincinnati, 2008.<br>Advisor: Yijun Liu. Title from electronic thesis title page (viewed Feb.25, 2009). Includes abstract. Keywords: Honeycomb; FGM; BEM; FEM. Includes bibliographical references.
10
Sivakumar, V. "Processing, Characterization And Evaluation Of A Functionally Graded Ai - 4.6% Cu Alloy." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/183.
Testo completoAbstract (sommario):
In some applications the stress across the entire cross-section of a component is not uniform but varies with position. For example, maximum shear stress is highest at the inner surface of a thick-walled cylinder subjected to uniform internal pressure and it decreases continuously towards the outer surface. In such applications it would be more appropriate for the component, too, to have varying strength across the cross-section matching with the stress profile it is subjected to. The present work deals with obtaining such a functionally graded material (FGM), characterizing it and testing its mechanical properties in compression.
Differential aging heat treatment was used to produce the functionally graded material in a precipitation hardenable Al-4.6%Cu alloy by changing the microstructure. Temperature gradient furnace was used to achieve the gradation in microstructure from one end of the sample to the other end by differential aging of the solution treated sample. Mechanical properties can be varied in any precipitation hardenable alloy by means of producing various precipitates, which will form during the aging sequence. In Al-4.6%Cu alloy one end of the solution treated sample was aged for 38 hours at 170°C and the other end at 70°C by means of a temperature gradient furnace in which the coil density varies along the axis of the furnace. Thus we achieved a difference in mechanical properties from 70°C side to 170°C side as the precipitation during differential aging varied from GP zones at one end to θ' precipitate at the other end.
Characterization was done on isothermally aged samples and in FGM using XRD (X-ray diffraction) and TEM (Transmission Electron Microscopy). XRD result showed that the final equilibrium precipitate θ was not formed in any of the heat-treated samples. TEM result showed the various precipitation sequences from GP zones to θ' in the isothermally aged samples and the same was confirmed in the gradient sample by cutting the samples form 70°C side towards the 170°C side and doing TEM on each sample.
The properties of FGM in compression were studied using a 9mmx9mmxl8mm-compression sample using DARTEC machine and it was compared with those of isothermally aged samples. For 70°C the 0.2% proof stress was 141MPa and for 170°C it was 226MPa. The corresponding ductility values at the point of inflection on the engineering stress-strain curve for 70°C sample was higher (33%) than the 170°C (22%) sample. For the gradient sample it gave a proof stress of 163MPa and a ductility value of 30%.
11
Sivakumar, V. "Processing, Characterization And Evaluation Of A Functionally Graded Ai - 4.6% Cu Alloy." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/183.
Testo completoAbstract (sommario):
In some applications the stress across the entire cross-section of a component is not uniform but varies with position. For example, maximum shear stress is highest at the inner surface of a thick-walled cylinder subjected to uniform internal pressure and it decreases continuously towards the outer surface. In such applications it would be more appropriate for the component, too, to have varying strength across the cross-section matching with the stress profile it is subjected to. The present work deals with obtaining such a functionally graded material (FGM), characterizing it and testing its mechanical properties in compression.
Differential aging heat treatment was used to produce the functionally graded material in a precipitation hardenable Al-4.6%Cu alloy by changing the microstructure. Temperature gradient furnace was used to achieve the gradation in microstructure from one end of the sample to the other end by differential aging of the solution treated sample. Mechanical properties can be varied in any precipitation hardenable alloy by means of producing various precipitates, which will form during the aging sequence. In Al-4.6%Cu alloy one end of the solution treated sample was aged for 38 hours at 170°C and the other end at 70°C by means of a temperature gradient furnace in which the coil density varies along the axis of the furnace. Thus we achieved a difference in mechanical properties from 70°C side to 170°C side as the precipitation during differential aging varied from GP zones at one end to θ' precipitate at the other end.
Characterization was done on isothermally aged samples and in FGM using XRD (X-ray diffraction) and TEM (Transmission Electron Microscopy). XRD result showed that the final equilibrium precipitate θ was not formed in any of the heat-treated samples. TEM result showed the various precipitation sequences from GP zones to θ' in the isothermally aged samples and the same was confirmed in the gradient sample by cutting the samples form 70°C side towards the 170°C side and doing TEM on each sample.
The properties of FGM in compression were studied using a 9mmx9mmxl8mm-compression sample using DARTEC machine and it was compared with those of isothermally aged samples. For 70°C the 0.2% proof stress was 141MPa and for 170°C it was 226MPa. The corresponding ductility values at the point of inflection on the engineering stress-strain curve for 70°C sample was higher (33%) than the 170°C (22%) sample. For the gradient sample it gave a proof stress of 163MPa and a ductility value of 30%.
12
Thomas, Gareth James. "Advanced materials for plasma facing components in fusion devices." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:f8ba1ae1-f303-4c32-877e-dca421a3cb5c.
Testo completoAbstract (sommario):
This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.
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Odorczyk, Marcos Fernando. "Uma estratégia numérica para análise termoelástica de sólidos recobertos com filmes de material funcionalmente gradado (FGM)." Universidade do Estado de Santa Catarina, 2011. http://tede.udesc.br/handle/handle/1796.
Testo completoAbstract (sommario):
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Previous issue date: 2011-07-29<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The finite element method has been traditionally applied in solving problems of elasticity and heat transfer, being widely used in cases with homogeneous isotropic materials. With the advent of new technologies, it has been more frequent to use components with more than one material, aiming to get the most out of each phase. A common example is the application of coating films, with optimal properties, on a substrate. These coating films may be homogeneous or functionally graded (FGM). The latter presents a continuous variation of properties through the geometry, allowing to reduce differences at the interface with the substrate. It is important to analyze the behavior of stresses along the interface between film and substrate, a region prone for the occurrence of failure. As current commercial finite element programs have limitations to handle FGM's, especially at the interfaces, one of the motivations of this dissertation is to develop a method for stress and flux nodal recovery, adequate to work with this type of material. The work presents the analysis of a component made of steel or aluminum coated with a titanium nitride film (homogeneous or FGM) under thermo-mechanical loading. The thermal part of the problem is set in an Eulerian description, leading to heat transfer by conduction and convection in the solid. The mechanical (elasticity) part is set in the usual Lagrangean description. A staggered thermo-mechanical approach is implemented and promising results are obtained.<br>O método de elementos finitos tem sido tradicionalmente aplicado na solução de problemas de elasticidade e transferência de calor, sendo amplamente utilizado em casos com materiais homogêneos e isotrópicos. Com o advento de novas tecnologias tem sido mais freqüente a utilização de componentes com mais de um material, onde se procura obter o máximo proveito de cada fase. Um exemplo comum é a aplicação de filmes de revestimento com propriedades ótimas sobre um substrato. Estes filmes de revestimento podem ser homogêneos ou funcionalmente gradados (FGM), sendo que o último tem variação continua de propriedades ao longo da geometria, permitindo atenuar diferenças na interface com o substrato. A análise do comportamento das tensões ao longo da interface entre filme e substrato é de suma importância, pois esta é uma região potencial para ocorrência de falhas. Dado que programas comerciais de elementos finitos atuais apresentam limitações para lidar com FGM s, principalmente na região de interface, uma das motivações desta dissertação é desenvolver um método de pós-processamento de tensões e fluxos capaz de trabalhar adequadamente com este tipo de material. O trabalho apresenta a análise de um componente de aço ou alumínio revestido com filme de nitreto de titânio (homogêneo ou funcionalmente gradado), sob carregamento termomecânico. A parte térmica do problema é descrita usando uma abordagem Euleriana, que resulta em condução de calor por convecção e condução no sólido. A parte mecânica (elasticidade) é descrita pela tradicional abordagem Lagrangeana. Um procedimento de solução termomecânica aninhada (staggered) é implementado e resultados promissores são obtidos.
14
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.
Testo completoAbstract (sommario):
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.<br>Godkänd; 1999; 20070320 (ysko)
15
Hauber, Brett Kenneth. "Fatigue Crack Propagation in Functionally Graded Materials." University of Dayton / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1259881312.
Testo completo
16
Heidari, Maryam. "3D modelling of functionally graded coatings." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=215382.
Testo completoAbstract (sommario):
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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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.
Testo completoAbstract (sommario):
In today'<br>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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Boidot, Mathieu. "Élaboration de revêtements γ-γ' et de systèmes barrière thermique par Spark Plasma Sintering : tenue au cyclage thermique et propriétés d’usage". Phd thesis, Toulouse, INPT, 2010. http://oatao.univ-toulouse.fr/11972/1/boidot.pdf.
Testo completoAbstract (sommario):
Les procédés existant pour la fabrication de sous-couches et de systèmes barrière thermique pour les aubes mobiles des turbomachines sont complexes, onéreux, et, de leur reproductibilité dépend la durée de vie de ces systèmes. Cette étude montre la faisabilité d'obtention de sous-couches γ-Ni + γ'-Ni3Al enrichies en platine et de systèmes barrière thermique complets, par l'utilisation du procédé de Spark Plasma Sintering (SPS). Les paramètres du procédé SPS (pression, durée, température et nombre de paliers) ont été ajustés afin de fabriquer les différents types de systèmes. Des améliorations ont été apportées à l'outillage, en vue notamment de mieux appréhender la température de la pièce lors du cycle thermique et, d'empêcher la formation de carbures. Les propriétés microstructurales des revêtements obtenus sont caractérisées et mises en relation avec les paramètres d'élaboration. De plus, les propriétés d'usage (cinétique d'oxydation, résistance au cyclage thermique et à la corrosion par les aluminosilicates fondus, CMAS, conductivité thermique) ont été évaluées. Un large domaine de composition de sous-couches a pu être exploré, notamment par l'addition, par pulvérisation cathodique, d'éléments réactifs (Hf, Y, Si) et d'autres éléments (Ag, Au, Cu) ayant un effet sur le domaine de stabilité de la phase γ'. La possibilité de réaliser des systèmes barrière thermique mono et bi-couches céramiques en une seule étape par le procédé SPS est également démontrée. Un mode d'endommagement spécifique des systèmes barrière thermique élaborés par SPS a été mis en évidence lors d'essais de cyclage thermique et interprété avec l'aide de simulations numériques par éléments finis. Les nombreuses compositions et architectures réalisées au cours de cette étude, sont un encouragement à poursuivre les améliorations apportées au procédé pour l'obtention de systèmes plus complexes et plus fiables.
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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.
Testo completoAbstract (sommario):
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.
20
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.
Testo completoAbstract (sommario):
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&rsquo<br>influence for a certain number of cyclic loading.
21
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.
Testo completo
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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.
Testo completoAbstract (sommario):
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.<br>Revisión por pares
23
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.
Testo completoAbstract (sommario):
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.
24
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.
Testo completo
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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.
Testo completo
26
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.
Testo completoAbstract (sommario):
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.
27
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.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Neste 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.<br>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.
28
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.
Testo completo
29
Oyekoya, Oyedele O. "Structural integrity of engineering components made of functionally graded materials." Thesis, Cranfield University, 2008. http://hdl.handle.net/1826/3802.
Testo completoAbstract (sommario):
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.
30
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.
Testo completo
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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.
Testo completo
32
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.
Testo completo
33
Wu, Kangjian [Verfasser]. "Process development for ZrO2-ZrSiO4/NiCr functionally graded materials / Kangjian Wu." Aachen : Shaker, 2013. http://d-nb.info/1050344340/34.
Testo completo
34
Caraballo, Simon. "Thermo-Mechanical Beam Element for Analyzing Stresses in Functionally Graded Materials." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3024.
Testo completoAbstract (sommario):
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.
35
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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Limmahakhun, Sakkadech. "Development of functionally graded materials for innovation in bone-replacement applications." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/108053/2/Sakkadech_Limmahakhun_Thesis.pdf.
Testo completoAbstract (sommario):
This project aims to develop bone-mimic structures for bone-replacement applications. To mimic the complex structures observed in bones, various internal architectures and graded cellular microstructures were created using additive manufacturing approaches to tailor the mechanical performance of polymer and metal based scaffolds. The structure-property relation, stress shielding effect and cell response were investigated using experimental and numerical methods, at different material length scales. The optimized architectures and graded microstructures were applied to femoral implants whose performance was also investigated via mechanical testing and numerical simulations. The findings of this thesis will help develop new strategies for bone replacement.
37
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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Cantergiani, Elisa. "Mechanical Properties of Functionally Graded Materials: Carbon Gradient inside Interstitial Free Steel." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34314.
Testo completoAbstract (sommario):
In the last decade aluminium started to be considered as an alternative to steel to produce car body panels, especially considering the strict demands to decrease fuel consumption which require vehicle weight reduction. In order to keep their leading role, steel companies have to produce stronger materials to reduce the thickness of steel sheets used in cars and are now considering non-conventional steel making processes.
The purpose of this PhD research was to investigate the possibility of strengthening thin sheets of interstitial free steel (IF steel) by using carbon rich films deposited on the steel surface using Physical Vapour Deposition (PVD). These films then act as a carbon reservoir which upon heat treatment release carbon in the IF steel and strengthen it.
Coated tensile coupons 200 μm thick were annealed at different temperatures under high vacuum. Tensile tests show that a 100 MPa increase in yield stress can be obtained after annealing at 430 ˚C for 1h in high vacuum. The effects of annealing environment, film thickness and prestrain on carbon diffusion were also investigated. It was shown that carbon diffusion from the film to the IF steel substrate is limited by the film transformation into cementite at temperatures equal or higher than 530 ˚C.
All tensile curves showed a plastic instability known as Lüders plateau, which is undesirable as it results in surface markings on the deformed part. FEM analyses were performed to find ways to suppress the Lüders plateau, proving that increasing strain-hardening or having a graded instead of uniform carbon content through thickness can suppress or limit Lüdering.
The possibility of creating a through thickness gradient of microstructure was investigated as it could suppress Lüdering and result in higher strength. For these tests, FeC coated coupons were induction heated to 820 ˚C followed by water quenching. After only 2 minutes of heat treatment the yield stress was increased by 250 MPa and the ultimate tensile strength reached 400 MPa. With an annealing of 4 minutes, the Lüders plateau was fully suppressed and the microstructure consisted in ferrite grains and TiC nanocarbides. This work demonstrates that FeC films can be effectively used to diffuse carbon into steel and that a significant increase in mechanical properties can be obtained after a heat treatment of only a few minutes.
39
Grigoriadis, Kostas. "Computational and conceptual blends : the epistemology of designing with functionally graded materials." Thesis, Royal College of Art, 2018. http://researchonline.rca.ac.uk/3401/.
Testo completoAbstract (sommario):
Operating within the landscape of new materialism and considering recent advances in the field of additive manufacturing, the thesis is proposing a novel method of designing with a new type of material that is known as functionally graded. Two of the additive manufacturing advances that are considered of radical importance and at the same time are central to the research have to do with the progressively increasing scales of the output of 3D printing, as well as with the expanding palette of materials that can now be utilised in the process. Regarding the latter, there are already various industrial research initiatives underway that explore ways that various materials can be combined in order to allow for the additive manufacturing of multi-material (otherwise known as functionally graded material) parts or whole volumes that are continuously fused together. In light of this and pre-empting this architectural-level integration and fusing of materials within one volume, the research initially outlines the anticipated impacts of the new way of building that this technology heralds. Of a total of six main anticipated changes, it then focuses on the impact that functionally graded materiality will have on how design is practiced. In this attempt to deal with the uncertainty of a material realm that is unruly and wilful, an initial criticism posed of the scant existing methods for designing with multi-materials in the computer is that they do not consider the intrinsic behaviour of materials and their natural propensity to structure themselves in space. Additionally, these models essentially follow a similarly arbitrary assignment of sub-materiality within larger multi-materials, to the hylomorphic imposition of form on matter. What is effectively proposed as a counter design technique is to computationally ‘predict’ the way materials will fuse and self-structure, with this self-arrangement being partially instigated by their physical properties. Correspondingly, this approach instigates two main objectives that will be pursued in the thesis: – The first goal, is to formulate an appropriate epistemology (also known as the epistemology of computer simulations-EOCS), which is directly linked to the use of computer simulations to design with (computational blending). This is effectively the creation of a methodological framework for the way to set out, run, and evaluate the results of the simulations. – The second goal, concerns the new design methodology proposed, in which the conventional material-less computer aided design methods are replaced by a process of constructing b-rep moulds and allowing digital materials to fuse with one another within these virtual frameworks. Drawing from a specific strand of materialist and cognitive theory (conceptual blending), the theoretical objective in effect is to demonstrate that form and material are not separate at any instance of the proposed process. The resulting original contribution of the design research is a process model that is created in an existing simulation software that can be used in a standard laptop computer in order to design with functionally graded materials. The various ‘stages’ of this model are mapped as a diagrammatic design work ow in the concluding end of the PhD, while its main parts are expanded upon extensively in corresponding chapters in the thesis.
40
Kidane, Addis Asmelash. "An experimental and analytical study of graded materials under thermo-mechanical dynamic loading /." View online ; access limited to URI, 2009. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3380532.
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Morton, Sean (Sean C. ). "Diffusional stability studies of a T91/12Cr-2Si-Fe functionally graded composite." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/106724.
Testo completoAbstract (sommario):
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.<br>MIT Institute Archives copy: incomplete; ends at page 7.<br>Includes bibliographical references (leaf 16 ).<br>by Sean Morton.<br>S.B.
42
Handra. "Application and economic feasibility of functionally graded composite for lead-bismuth service." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45390.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.<br>Includes bibliographical references (p. 57-60).<br>Use of materials in liquid Pb/Pb-Bi systems in the higher temperature (550°C-700°C) in advanced liquid metal cooled advanced reactor systems is limited by their corrosion resistance. To address this issue, an Fe-12Cr-2.55Si alloy system is being developed and researched, and when used along with T91 (9Cr-lMo) as base material, it will be applicable in tubes production mainly for advanced LBE (Lead-Bismuth Eutectic) reactor systems. An analysis was carried out on this new technology's benefits and its commercialization to evaluate whether or not the technology has economic feasibility if it then is used and commercialized in LBE nuclear industry. The results indicate that this new material has potential to be favored. Before coming to this conclusion, factors such as examination of IP landscape & competing technologies, current and potential of competitiveness of the LBE reactors and the new materials, and a simple business strategic & entry market analysis have been conducted.<br>by Handra.<br>M.Eng.
43
Nandakumar, Nagarajan Nicholson P. S. "Nickel-alumina composites and graded materials by electrophoretic deposition /." *McMaster only, 2005.
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44
Yıldırım, Uygar Güden Mustafa. "Investigation of quasi-static dynamic mechanical properties of functionally graded Sic-particulate reinforced aluminium metal matrix composites/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/makinamuh/T000470.doc.
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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.
Testo completoAbstract (sommario):
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.
46
Uzun, Huseyin. "Fabrication and mechanical properties of SiCâ†(â†pâ†) /Al-2124 functionally graded materials." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341935.
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Gandra, João Pedro Machado da. "Preliminary study on the production of functionally graded materials by friction stir processing." Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4889.
Testo completoAbstract (sommario):
Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Mecânica<br>An investigation was carried out to evaluate the potential application of Friction Stir Processing (FSP) to produce Functionally Graded Materials (FGM‟s).
Friction stir processed materials can be considered as FGM‟s since the localized microstructural modification results in a gradual property modification. Therefore, to enhance hardness and ductility at specific superficial levels, surface layers of processed material were produced by multiple-pass FSP with an overlap ratio of 0.5. Overlapping was done on the advancing (AS) and retreating sides (RS) to study potential differences on the resulting mechanical properties. It was observed that processing in these two conditions led to different surface topography, since overlapping by the advancing side resulted in a wave-like surface profile.
The mechanisms involved in FSP also led to its exploitation for the production of particle-reinforced Metal Matrix Composite (MMC) materials, as the severe plastic deformation produced during the process promotes the dispersion of the particles within the matrix. An investigation was conducted in order to produce aluminium based functionally graded MMCs reinforced by SiC ceramic particles with median size of 118.8, 37.4 and 12.3 micron. AA5083 aluminium alloy plates in the H111 and partially annealed conditions were processed. Several strategies for reinforcement were investigated and its influence on the particle distribution and homogeneity. The most promising results were achieved when the pin fully overlapped the groove. SiC fraction area analysis revealed two orthogonal gradients. Since FSP was used as a surface processing technique, the magnitude of the microstructural effects generated by the tool gradually decreases along the depth of the processed material. A second gradient was generated parallel to the bead surface due to the asymmetric nature of material flow around the tool. The use of smaller sized particles led to more homogeneous composite layers and smother gradients. Tool wear was very significant, proving that SiC reinforcement is not the most suitable method to produce FGM‟s.
48
Jain, Nitesh. "Experiment and analytical evaluation of dynamic fracture in graded multifunctional materials /." View online ; access limited to URI, 2005. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3188059.
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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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Shi, Chao. "Finite Block Method and applications in engineering with Functional Graded Materials." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/39764.
Testo completoAbstract (sommario):
Fracture mechanics plays an important role in understanding the performance of all types of materials including Functionally Graded Materials (FGMs). Recently, FGMs have attracted the attention of various scholars and engineers around the world since its specific material properties can smoothly vary along the geometries. In this thesis, the Finite Block Method (FBM), based on a 1D differential matrix derived from the Lagrangian Interpolation Method, has been presented for the evaluation of the mechanical properties of FGMs on both static and dynamic analysis. Additionally, the coefficient differential matrix can be determined by a normalized local domain, such as a square for 2D, a cubic for 3D. By introducing the mapping technique, a complex real domain can be divided into several blocks, and each block is possible to transform from Cartesian coordinate (xyz) to normalized coordinate (ξησ) with 8 seeds for two dimensions and 20 seeds for three dimensions. With the aid of coefficient differential matrix, the differential equation is possible to convert to a series of algebraic functions. The accuracy and convergence have been approved by comparison with other numerical methods or analytical results. Besides, the stress intensity factor and T-stresses are introduced to assess the fracture characteristics of FGMs. The Crack Opening displacement is applied for the calculation of the stress intensity factor with the FBM. In addition, a singular core is adopted to combine with the blocks for the simulation of T stresses. Numerical examples are introduced to verify the accuracy of the FBM, by comparing with Finite Element Methods or analytical results. Finally, the FBM is applied for wave propagation problems in two- and three-dimensional porous mediums considering their poroelasticities. To demonstrate the accuracy of the present method, a one-dimensional analytical solution has been derived for comparison.