Dissertations / Theses: 'Elastic materials'

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Paine, A. C. "Elastic properties of granular materials." Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245957.

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Schenck, David Robert. "Some Formation Problems for Linear Elastic Materials." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28608.

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Some equations of linear elasticity are developed, including those specific to certain actuator structures considered in formation theory. The invariance of the strain-energy under the transformation from rectangular to spherical coordinates is then established for use in two specific formation problems. The first problem, involving an elastic structure with a cylindrical equilibrium configuration, is formulated in two dimensions using polar coordinates. It is shown that $L^2$ controls suffice to obtain boundary displacements in $H^{1/2}$. The second problem has a spherical equilibrium configuration and utilizes the elastic equations in spherical coordinates. Results similar to those obtained in the two dimensional case are indicated for the three dimensional problem.
Ph. D.

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3

Rodrigues, Ferreira Elizabete. "Finite-amplitude waves in deformed elastic materials." Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210464.

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Le contexte de cette thèse est la théorie de l'élasticité non linéaire, appelée également "élasticité finie". On y présente des résultats concernant la propagation d'ondes d'amplitude finie dans des matériaux élastiques non linéaires soumis à une grande déformation statique homogène. Bien que les matériaux considérés soient isotropes, lors de la propagation d'ondes un comportement anisotrope dû à la déformation statique se manifeste.

Après un rappel des équations de base de l'élasticité non linéaire (Chapitre 1), on considère tout d'abord la classe générale des matériaux incompressibles. Pour ces matériaux, on montre que la propagation d'ondes transversales polarisées linéairement est possible pour des choix appropriés des directions de polarisation et de propagation. De plus, on propose des généralisations des modèles classiques de "Mooney-Rivlin" et "néo-Hookéen" qui conduisent à de nouvelles solutions. Bien que le contexte soit tri-dimensionnel, il s'avère que toutes ces ondes sont régies par des équations d'ondes scalaires non linéaires uni-dimensionelles. Dans le cas de solutions du type ondes simples, on met en évidence une propriété remarquable du flux et de la densité d'énergie.

Dans les Chapitres 3 et 4, on se limite à un modèle particulier de matériaux compressibles appelé "modèle restreint de Blatz-Ko", qui est une version compressible du modèle néo-Hookéen.

En milieu infini (Chapitre 3), on montre que des ondes transversales polarisées linéairement, faisant intervenir deux variables spatiales, peuvent se propager. Bien que la théorie soit non linéaire, le champ de déplacement de ces ondes est régi par une version anisotrope de l'équation d'onde bi-dimensionnelle classique. En particulier, on présente des solutions à symétrie "cylindrique elliptique" analogues aux ondes cylindriques. Comme cas particulier, on obtient aussi des ondes planes inhomogènes atténuées à la fois dans l'espace et dans le temps. De plus, on montre que diverses superpositions appropriées de solutions sont possibles. Dans chaque cas, on étudie les propriétés du flux et de la densité d'énergie. En particulier, dans le cas de superpositions il s'avère que des termes d'interactions interviennent dans les expressions de la densité et du flux d'énergie.

Finalement (Chapitre 4), on présente une solution exacte qui constitue une généralisation non linéaire de l'onde de Love classique. On considère ici un espace semi-infini, appelé "substrat" recouvert par une couche. Le substrat et la couche sont constitués de deux matériaux restreints de Blatz-Ko pré-déformés. L'onde non linéaire de Love est constituée d'un mouvement non atténué dans la couche et d'une onde plane inhomogène dans le substrat, choisies de manière à satisfaire aux conditions aux limites. La relation de dispersion qui en résulte est analysée en détail. On présente de plus des propriétés générales du flux et de la densité d'énergie dans le substrat et dans la couche.

The context of this thesis is the non linear elasticity theory, also called "finite elasticity".

Results are obtained for finite-amplitude waves in non linear elastic materials which are first subjected to a large homogeneous static deformation. Although the materials are assumed to be isotropic, anisotropic behaviour for wave propagation is induced by the static deformation.

After recalling the basic equations of the non linear elasticity theory (Chapter 1), we first consider general incompressible materials. For such materials, linearly polarized transverse plane waves solutions are obtained for adequate choices of the polarization and propagation directions (Chapter 2). Also, extensions of the classical Mooney-Rivlin and neo-Hookean models are introduced, for which more solutions are obtained. Although we use the full three dimensional elasticity theory, it turns out that all these waves are governed by scalar one-dimensional non linear wave equations. In the case of simple wave solutions of these equations, a remarkable property of the energy flux and energy density is exhibited.

In Chapter 3 and 4, a special model of compressible material is considered: the special Blatz-Ko model, which is a compressible counterpart of the incompressible neo-Hookean model.

In unbounded media (Chapter 3), linearly polarized two-dimensional transverse waves are obtained. Although the theory is non linear, the displacement field of these waves is governed by a linear equation which may be seen as an anisotropic version of the classical two-dimensional wave equation. In particular, solutions analogous to cylindrical waves, but with an "elliptic cylindrical symmetry" are presented. Special solutions representing "damped inhomogeneous plane waves" are also derived: such waves are attenuated both in space and time. Moreover, various appropriate superpositions of solutions are shown to be possible. In each case, the properties of the energy density and the energy flux are investigated. In particular, in the case of superpositions, it is seen that interaction terms enter the expressions for the energy density and the energy flux.

Finally (Chapter 4), an exact finite-amplitude Love wave solution is presented. Here, an half-space, called "substrate", is assumed to be covered by a layer, both made of different prestrained special Blatz-Ko materials. The Love surface wave solution consists of an unattenuated wave motion in the layer and an inhomogeneous plane wave in the substrate, which are combined to satisfy the exact boundary conditions. A dispersion relation is obtained and analysed. General properties of the energy flux and the energy density in the substrate and the layer are exhibited.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Muscat-Fenech, Claire. "Tearing of sheet materials." Thesis, University of Reading, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317039.

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5

Si, Xiuhua. "Applications of the thermodynamics of elastic, crystalline materials." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4177.

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The thermodynamic behaviors of multicomponent, elastic, crystalline solids under stress and electro-magnetic fields are developed, including the extension of EulerÃ¢ÂÂs equation, Gibbs equation, Gibbs-Duhem equation, the conditions to be expected at equilibrium, and an extension of the Gibbs phase rule. The predictions of this new phase rule are compared with experimental observations. The stress deformation behaviors of the single martensitic crystal with and without magnetic fields were studied with the stress deformation equation derived by Slattery and Si (2005). One coherent interfacial condition between two martensitic variants was developed and used as one boundary condition of the problem. The dynamic magnetic actuation process of the single crystal actuator was analyzed. The extension velocity and the actuation time of the single crystal actuator are predicted. The relationship between the external stress and the extension velocity and the actuation time with the presence of a large external magnetic field was studied. The extended Gibbs-Duhem equation and Slattery-Lagoudas stress-deformation expression for crystalline solids was used. Interfacial constraints on the elastic portion of stress for crystalline-crystalline interfaces and crystalline-fluids or crystallineamorphous solids interfaces were derived and tested by the oxidation on the exterior of a circular cylinder, one-sided and two-sided oxidation of a plate. An experiment for measuring solid-solid interface surface energies was designed and the silicon-silicon dioxide surface energy was estimated. A new generalized Clausius-Clapeyron equation has been derived for elastic crystalline solids as well as fluids and amorphous solids. Special cases are pertinent to coherent interfaces as well as the latent heat of transformation.

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Guastavino, Rémi. "Elastic and acoustic characterisation of anisotropic porous materials." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4782.

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For an accurate prediction of the low and medium frequency surface vibration and sound radiation behaviour of porous materials, there is a need to improve the means of estimating their elastic and acoustic properties. The underlying reasons for this are many and of varying origin, one prominent being a poor knowledge of the geometric anisotropy of the cell microstructure in the manufactured porous materials. Another one being, the characteristic feature of such materials i.e. that their density, elasticity and dissipative properties are highly dependent upon the manufacturing process techniques and settings used. In the case of free form moulding, the geometry of the cells and the dimensions of the struts are influenced by the rise and injection flow directions and also by the effect of gravity, elongating the cells. In addition the influence of the boundaries of the mould also introduces variations in the properties of the foam block produced. Despite these complications, the need to predict and, in the end, optimise the acoustic performance of these materials, either as isolated components or as part of a multi-layer arrangement, is growing. It is driven by the increasing demands for an acoustic performance in balance with the costs, a focus which serves to increase the need for modelling their behaviour in general and the above mentioned, inherent, anisotropy in particular. The current work is focussing on the experimental part of the characterisation of the material properties which is needed in order to correctly represent the anisotropy in numerical simulation models. Then an hybrid approach based on a combination of experimental deformation, strain field mapping, flow resistivity measurement and physically based porous material acoustic Finite Element (FE) simulation modelling is described. This inverse estimation linked with high quality measurements is crucial for the determination of the anisotropic coefficients of the porous materials is illustrated here for soft foam and fibrous wool materials.
QC 20100729

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7

Ragauskas, Paulius. "Identification Of Elastic Properties Of Layered Composite Materials." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101119_134738-62490.

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In this thesis the problems of identification accuracy of elastic properties of materials are examined. The main object of study is samples of various materials and their elastic properties. This is an important subject of theoretical studies of various materials. The main thesis objective is to create an effective technology for precise identification of all the elastic characteristics of the sample. The de-veloped algorithms are to be applied in the material manufacturing industry. Thesis also aims at exploring accuracy and sensitivity of the identification of elastic properties of materials. The paper deals with a number of objectives: 1) to optimize the geometric parameters of the sample striving for more accurate identification results of elas-tic properties; 2) to identify mode shapes of sample and regulate their place in spectrum of eigenvalues in order to minimize the distortion of the objective function; 3) to create the implementation algorithms of proposed technologies and verify their capabilities experimentally. The first task is formulated taking into account the relatively high level of identification error of elastic properties of composite materials. The second objective relates to distortion of the objec-tive function in the process of updating the mathematical model with the pre-sumed elastic characteristics of material. The thesis is composed of four chapters, the summary of results, the list of literature and the list of author’s publications on the topic... [to full text]
Disertacijoje nagrinėjamos medžiagų tamprumo rodiklių identifikavimo tikslumo problemos. Pagrindinis tyrimo objektas yra įvairių medžiagų bandiniai, jų tamprumo rodikliai. Šis objektas yra svarbus įvairių medžiagų teoriniams tyrimams. Pagrindinis disertacijos tikslas yra sukurti efektyvią technologiją, leidžiančią pakankamu tikslumu surasti visus bandinio tamprumo rodiklius. Sukurtų algoritmų taikymo sritis yra medžiagų gamybos pramonė. Disertacijoje tiriamas siūlomos technologijos tikslumas ieškant įvairių medžiagų tamprumo rodiklių. Darbe sprendžiami keli pagrindiniai uždaviniai: optimizuojami bandinio geometriniai parametrai siekiant tikslesnių tamprumo rodiklių identifikavimo rezultatų; atpažįstamos bandinio modų formos ir reguliuojama jų vieta tikrinių reikšmių spektre siekiant sumažinti tikslo funkcijos iškraipymus; sukuriami pasiūlytų technologijų įgyvendinimo algoritmai ir bandymais patikrinamos jų galimybės. Pirmasis uždavinys suformuluotas atsižvelgiant į palyginti didelę kompozitinių medžiagų tamprumo rodiklių identifikavimo paklaidą. Antrasis siejasi su tikslo funkcijos iškraipymu atnaujinant matematinį medžiagos modelį spėjamais tamprumo rodikliais. Disertaciją sudaro keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariamas problemos aktualumas, tyrimo objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų... [toliau žr. visą tekstą]

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Guastavino, Rémi. "Elastic and acoustic characterisation of anisotropic porous materials /." Stockholm : Department of Aeronautical and Vehicle Engineering, Royal Institute of Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4782.

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9

Jones, G. W. "Static Elastic Properties of Composite Materials Containing Microspheres." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487266.

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This thesis aims to model the uniaxial deformation of a class of materials consisting of microscopic spherical shells embedded in a rubber matrix. These shells are assumed to buckle as the stress on the material increases. To motivate the analysis we consider the paradigm problem of the debonding of a distribution of cylindrical inclusions in an elastic material undergoing antiplane shear, with bonded and debonded inclusions playing the role of unbuckled and buckled shells respectively. We begin the modelling of the microsphere-containing material by considering the buckling of an isolated embedded shell inclusion with a uniaxial stress field at infinity, using Koiter's theory of shallow shells. The resulting energy functional is solved as an eigenvalue problem by the Rayleigh-Ritz method. Subsequently, we analyse the buckling criterion asymptotically in the limit as the thickness ratio tends to zero by analogy with the WKB analysis of a beam on a variable-stiffness substrate. To model the shell after buckling we consider the simplified case of an embedded shell with a crack around its equator. The system is solved by expressing the displacements in the shell and matrix as series of Love stress functions, with the resulting infinite system of equations solved numerically with the aid of a convergence acceleration method. Finally we consider a composite material consisting of a homogenised dilute distribution of buckled and unbuckled shells, with the proportion of each type of shell dependent on the stress applied to the material, according to an asymptotic formula relating the size of the inclusions and the critical buckling stress that was obtained previously.

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10

Gregory, P. W. "Finite elastic-plastic deformations of highly anisotropic materials." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282601.

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11

Yan, Guowei. "Interactive Modeling of Elastic Materials and Splashing Liquids." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1593098802306904.

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12

Murugaiah, Anand Kalidindi Surya Barsoum Michel W. "Nanoindentations in kinking nonlinear elastic solids /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/316.

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13

Chang, Ting-Chieh. "Crack growth in an elastic-primary creeping material /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487259125219166.

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14

Sklar, Zenon. "Quantitative acoustic microscopy of coated materials." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308851.

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15

Josefsson, Gabriella. "Elasticity of Cellulose Nanofibril Materials." Doctoral thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-240250.

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The demand for renewable load-carrying materials is increasing with increasing environmental awareness. Alternative sources for materials manufacturing and design have to be investigated in order to replace the non-biodegradable materials. The work presented in this thesis investigates structure-property relations of such renewable materials based on cellulose nanofibrils. Cellulose is the most abundant polymer on earth and exists in both ordered and disordered phases, where the ordered crystalline cellulose shows excellent mechanical properties. The celluloses nanofibril is composed of partly crystalline cellulose where the stiff crystal regions, or crystallites, are orientated in the axial direction of the fibrils. The cellulose nanofibrils have a high aspect ratio, i.e. length to diameter ratio, with a diameter of less than 100 nm and a length of some micrometres. In the presented work, different properties of the cellulose nanofibril were studied, e.g. elastic properties, structure, and its potential as a reinforcement constituent. The properties and behaviour of the fibrils were studied with respect to different length scales, from the internal structure of the cellulose nanofibril, based on molecular dynamic simulations, to the macroscopic properties of cellulose nanofibril based materials. Films and composite materials with in-plane randomly oriented fibrils were produced. Properties of the cellulose nanofibril based materials, such as stiffness, thickness variation, and fibril orientation distribution, were investigated, from which the effective elastic properties of the fibrils were determined. The studies showed that a typical softwood based cellulose nanofibril has an axial stiffness of around 65 GPa. The properties of the cellulose nanofibril based materials are highly affected by the dispersion and orientation of the fibrils. To use the full potential of the stiff fibrils, well dispersed and oriented fibrils are essential. The orientation distribution of fibrils in hydrogels subjected to a strain was therefore investigated. The study showed that the cellulose nanofibrils have high ability to align, where the alignment increased with increased applied strain.

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Nurmela, Arto. "Non-Rutherford elastic scattering cross sections for materials analysis." Helsinki : University of Helsinki, 2001. http://ethesis.helsinki.fi/julkaisut/mat/fysii/vk/nurmela/.

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17

PACHECO, PEDRO MANUEL CALAS LOPES. "ANALYSIS OF THE THERMOMECHANICAL COUPLING IN ELASTIC-VISCOPLASTIC MATERIALS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1994. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33223@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A modelagem do acoplamento entre os fenômenos mecânicos e térmicos em sólidos inelásticos é considerada neste trabalho. O acoplamento termomecânico é importante em determinadas situações, como por exemplo, no estudo de problemas envolvendo deformações inelásticas cíclicas em estruturas metálicas. Um procedimento sistemático para obtenção de equações constitutivas termodinamicamente admissíveis é apresentado. Através deste procedimento, baseado na Termodinâmica dos Processos Irreversíveis, foi possível obter uma teoria constitutiva para modelar o comportamento anisotérmico de metais e ligas metálicas. Dois tipos de acoplamentos termomecânicos foram identificados: o acoplamento interno, associado à dissipação interna do processo mecânico, e o térmico, associado à dependência dos parâmetros das equações constitutivas com a temperatura. A teoria foi particularizada para materiais elasto-viscoplásticos. Simulações com barras foram realizadas para estudar fenômenos como o aquecimento de metais provocado por solicitações mecânicas complexas e o comportamento de metais submetidos a grandes gradientes de temperatura. Uma variável de dano foi incorporada ao modelo, permitindo estudar a influência do acoplamento termodinâmico em processos de degradação do material como fadiga de baixo ciclo.
The present work is concerned with the modeling of the coupling between mechanical and termal phenomena. The thermomechanical coupling is important in some problems like those involving inelastic cyclic deformation in metallic structures. A systematic procedure to obtain thermodynamically admissible constitutive equations is presented. Such procedure has a strong thermodynamic basis and is used to obtain a constant theory to model the anisothermal behavior of metals and alloys. Two kinds of thermomechanical couplings can be identified: the internal coupling, related with the internal dissipation in the mechanical process and the thermal coupling, related with the dependence of the material parameters in the constitutive equations on temperature. The theory is particularized to elasto-viscoplastic materials. Uniaxial simulations were performed to study the heating of metals due to complex mechanical loadings and the behavior of metals subjected to high temperature gradients. A damage variable is introduced in the model to study the influence of the thermomechanical coupling in processes involving the degradation of the material like in low-cycle fatigue.

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18

Arnold, Nazmiye Ertan. "Void initiation in a class of compressible elastic materials." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14918.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 40-41.
by Nazmiye Ertan Arnold.
M.S.

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19

Tsarouchas, Dimitris. "Fibre network materials : architecture and effective linear elastic properties." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610878.

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Tudela, Mark A. "Impact response of a laminated beam on an elastic foundation." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17880.

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Zhou, Aiguo Barsoum M. W. Barsoum M. W. Kalidindi Surya. "Kinking nonlinear elastic solids : theory and experiments /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2804.

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Akarapu, Sreekanth. "Numerical analysis of plane cracks in strain-gradient elastic materials." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/S%5FAkarapu%5F082205.pdf.

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Kusuma, Jeffry. "On some mathematical aspects of deformations of inhomogeneous elastic materials /." Title page, contents and summary only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phk97.pdf.

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Idjimarene, Sonia. "Power laws behavior and nonlinearity mechanisms in mesoscopic elastic materials." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-01037944.

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Nonlinear mesoscopic elastic (NME) materials present ananomalous nonlinear elastic behavior, which could not beexplained by classical theories. New physical mechanismsshould be individuated to explain NMEs response.Dislocations in damaged metals, fluids in rocks andadhesion (in composites) could be plausible. In this thesisI have searched for differences in the macroscopic elasticresponse of materials which could be ascribed to differentphysical processes. I have found that the nonlinearindicators follow a power law behavior as a function of theexcitation energy, with exponent ranging from 1 to 3 (thisis not completely new). This allowed to classify materialsinto well-defined classes, each characterized by a value ofthe exponent and specific microstructural properties. Tolink the measured power law exponent to plausiblephysical mechanisms, I have extended thePreisach-Mayergoyz formalism for hysteresis to multi-statemodels. Specific multi-state discrete models have beenderived from continuous microscopic physical processes,such as adhesion-clapping, adhesion-capillary forces,dislocations motion and hysteresis. In each model, themicroscopic behavior is described by a multistate equationof state, with parameters which are statisticallydistributed. Averaging over many microscopic elements theso-called mesoscopic equation of state is derived and, fromwave propagation simulations in a sample composed bymany mesoscopic elements, the experimental results couldbe reproduced. In the work of the thesis, I have shownthat model predictions of the exponent b ( the exponent bhas not been introduced before) are linked in a 'a priori'predictable way to the number of states and the propertiesof the statistical distribution adopted. We have classifiedmodels into classes defined by a different exponent b andcomparing with experimental results we have suggestedplausible mechanisms for the nonlinearity generation.

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DOMINGUES, STELLA MARIS PIRES. "ANALYSIS OF BRITTLE ELASTIC MATERIALS THROUGH A CONTINUOUS DAMAGE MODEL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1996. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33202@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho lida com uma teoria de dano contínuo, desenvolvida em um contexto termodinâmico, capaz de realizar uma descrição macroscópica da degradação de um material induzida pela deformação em estruturas elásticas frágeis (isto é, falha ocorre sem deformações permanentes). Na modelagem, supõe-se que a energia livre de Helmholtz não depende apenas da deformação e da temperatura absoluta, mas também da variável dano e de seu gradiente. Além disso, para levar em conta os efeitos microscópicos, a potência dos esforços internos não depende apenas da velocidade e de seu gradiente, mas também da taxa de evolução do dano e de seu gradiente. Apesar da sofisticação mecânica da teoria, uma técnica numérica simples, baseada no método dos elementos finitos, é proposta para aproximar a solução dos problemas matemáticos não lineares resultantes. Nestes problemas o acoplamento entre as variáveis dano e deformação é contornado por meio da técnica de partição dos operadores. Para validar o modelo e investigar as características principais do método numérico, diversos exemplos são apresentados para mostrar que os algoritmos utilizados não são sensíveis à malha (mesh dependent).
The present work deals with a continuum damage theory, developed within a thennodynamical framework, able to perform a macroscopic description of material degradation induced by deformation in brittle elastic structures (i.e. failure occurs without permanent deformations). In the modeling, the Helmholtz free energy is supposed to depend not only on the strain and on the absolute temperature but on a damage variable and its gradient as well. Besides, to account for microscopic effects, the power of internal forces depends not only on the velocity and its gradient, but also on the damage velocity and its gradient. Despite the mechanical sophistication of the theory, a simple numerical technique, based on the únite element method, is proposed to approximate the solution of the resulting non linear mathematical problems. The coupling between damage and strain variables in these problems is circumvented by means of a splitting technique. In order to analyse the physical coherence of the model and to access the main features of the numerical method, a number of examples is presented showing that the numerical computations are not mesh dependent.

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CHIMISSO, FULVIO ENRICO GIACOMO. "A CONTINUOUS DAMAGE MODEL FOR MATERIALS WITH ELASTIC-PLASTIC BEHAVIOR." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1994. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33238@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A Mecânica do Dano Contínuo é uma ferramenta promissora para a análise de vida residual em componentes de máquinas e de estruturas. Todavia, não é uma tarefa simples a de se obter uma descrição fisica realística, associada a uma descrição matemática correta, do acoplamento entre a deformação e o amolecimento causado pela degradação da microestrutura. No caso de barras metálicas, a deformação plástica cíclica causa um endurecimento junto com uma degradação na estrutura (dano de fadiga). Por outro lado, a degradação da estrutura induz o amolecimento observado na curva tensão de engenharia vs. deformação. Logo, torna-se importante a modelagem do acoplamento entre plasticidade e dano para que se possa prever de maneira adequada o tempo de vida (ciclos), de um componente estrutural. Muitas tentativas feitas para descrever este tipo de comportamento mostraram-se insatisfatórias. O problema matemático é, em geral, mal posto e uma aproximação numérica da solução é incorreta do ponto de vista fisico. Nestes casos, o fenômeno de localização da deformação é malha-dependente. No presente trabalho, propõe-se uma nova teoria de dano para materiais elasto-plásticos que supera este problema. A teoria tem uma forte base termodinâmica e leva em conta o fenômeno de amolecimento. Uma diferença básica em relação a outros modelos consiste no fato de que a variável escalar D, associada ao dano, é considerada não apenas uma variável de estado mas também uma variável cinemática independente, com abordagem semelhante à apresentada nas teorias de contínuo com microestrutura. As possibilidades de utilização da teoria apresentada são verificadas através da comparação de simulações numéricas com resultados experimentais, para solicitações cíclicas uniaxiais, em barras de almnínioestrutural e em barras de aço austenitico AISI 316 L.
Continuum Damage Mechanics is a promising tool for the failure prediction of structural components. Nevertheless, it is not a simple task to do a mathematically correct and physically realistic description of the strain-softcning behavior due to the degradation of the microstructure. In the case of metallic bars, the cyclic plastic deformation induces a strain-hardening and also a degradation of the structure (fatigue damage). In the other hand, the degradation of the structure induces a softening behavior in the engineering stress-strain curve. Hence, it is very important to model the coupling between plasticity and damage in order to perform an adequate lifetime prevision. Many attempts to describe this type of behavior have been unsatisfatory. The mathematical problem is, in general, ill posed and a numerical approximation of the solution is incorrect from the physical point of view. In this cases the phenomenon of strain localization due to strain-soflzening is mesh dependent. In the present work a new Damage theory for elasto-plastic materials that overcome this problem is proposed. The theory has a strong thermodynarnic basis and take into account the softening behavior. One basic difference from the others models is that the scalar variable D related with damage is taken as an independent kinematic variable, similarly as in the theories of continua with microstructure. The effectiveness and usefulness of the theory is checked by comparing numerical simulations of cyclic uniaxial tests in Aluminiun bars and 316L stainless steel bars with experimental results.

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27

Lacis, Ugis. "Models of porous, elastic and rigid materials in moving fluids." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195679.

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Tails, fins, scales, and surface coatings are used by organisms for various tasks, including locomotion. Since millions of years of evolution have passed, we expect that the design of surface structures is optimal for the tasks of the organism. These structures serve as an inspiration in this thesis to identify new mechanisms for flow control. There are two general categories of fluid-structure-interaction mechanisms. The first is active interaction, where an organism actively moves parts of the body or its entire body in order to modify the surrounding flow field (e.g., birds flapping their wings). The second is passive interaction, where appendages or surface textures are not actively controlled by the organism and hence no energy is spent (e.g., feathers passively moving in the surrounding flow). Our aim is to find new passive mechanisms that interact with surrounding fluids in favourable ways; for example, to increase lift and to decrease drag. In the first part of this work, we investigate a simple model of an appendage (splitter plate) behind a bluff body (circular cylinder or sphere). If the plate is sufficiently short and there is a recirculation region behind the body, the straight position of the appendage becomes unstable, similar to how a straight vertical position of an inverted pendulum is unstable under gravity. We explain and characterize this instability using computations, experiments and a reduced-order model. The consequences of this instability are reorientation (turn) of the body and passive dispersion (drift with respect to the directionof the gravity). The observed mechanism could serve as a means to enhance locomotion and dispersion for various motile animals and non-motile seeds. In the second part of this thesis, we look into effective models of porous and poroelastic materials. We use the method of homogenization via multi-scale expansion to model a poroelastic medium with a continuum field. In particular, we derive boundary conditions for the velocity and the pressure at the interface between the free fluid and the porous or poroelastic material. The results obtained using the derived boundary conditions are then validated with respect to direct numerical simulations (DNS) in both two-dimensional and three-dimensional settings. The continuum model – coupled with the necessary boundary conditions – gives accurate predictions for both the flow field and the displacement field when compared to DNS.
Många djur använder sig av fjäll, päls, hår eller fjädrar för att öka sin förmåga att förflytta sig i luft eller vatten. Eftersom djuren har genomgått miljontals år av evolution, kan man förvänta sig att ytstrukturernas form är optimala för organismens uppgifter. Dessa strukturer tjänar som inspiration i denna avhandling för att identifiera nya mekanismer för manipulering av strömning. Samverkan mellan fluider och strukturer (så kallad fluid-struktur-interaktion) kan delas upp i två kategorier. Den första typen av samverkan är aktiv, vilket innebär att en organism aktivt rör hela eller delar av sin kropp för att manipulera det omgivande strömningsfältet (till exempel fåglar som flaxar sina vingar). Den andra typen är passiv samverkan, där organismer har utväxter (svansar, fjärdar, etc.) eller ytbeläggningar som de inte aktivt har kontroll över och som således inte förbrukar någon energi. Ett exempel är fjädrar som passivt rör sig i det omgivande flödet. Vårt mål är att hitta nya passiva mekanismer som växelverkar med den omgivande fluiden på ett fördelaktigt sätt, exempelvis genom att öka lyftkraften eller minska luftmotståndet. I den första delen av detta arbete undersöker vi en enkel modell för en utväxt (i form av en platta) bakom en cirkulär cylinder eller sfär. Om plattan är tillräckligt kort och om det finns ett vak bakom kroppen kommer det upprätta läget av plattan att vara instabilt. Denna instabilitet är i princip samma som uppstår då man försöker balansera en penna på fingret. Vi förklarar den bakomliggande mekanismen av denna instabilitet genom numeriska beräkningar, experiment och en enkel modell med tre frihetsgrader. Konsekvenserna av denna instabilitet är en omorientering (rotation) av kroppen och en sidledsförflyttning av kroppen i förhållande till tyngdkraftens riktning. Denna mekanism kan användas djur och frön för att öka deras förmåga att förflytta eller sprida sig i vatten eller luft. I den andra delen av avhandlingen studerar vi modeller av porösa och elastiska material. Vi använder en mångskalig metod för att modellera det poroelastiska materialet som ett kontinuum. Vi härleder randvillkor för både hastighetsfältet och trycket på gränssnittet mellan den fria fluiden och det poroelastiska materialet. Resultaten som erhållits med de härledda randvillkoren valideras sedan genom direkta numeriska simuleringar (DNS) för både två- och tredimensionella fall. Kontinuumsmodellen av materialet kopplad genom randvillkoren till den fria strömmande fluiden predikterar strömnings- och förskjutningsfält noggrant i jämförelse med DNS.

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28

Ayub, Muhammad Azmi. "Automated two-dimensional patterned shape cutting of elastic web materials." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/35242.

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The objective of this thesis is to automate the manual 2D-patterned cutting of lace with high a accuracy and quality of the cutting edges. Four main problems for automating the cutting method were addressed; feature recognition technique for cutting path extraction, material handling system, laser beam manipulation and trajectory planning generation. An integrated mechatronic approach for designing the automated laser cutting system was outlined. The features of the 2D-patterned lace fabrics are not exactly identical and easily distorted nonlinearly due to handling operations. An active template matching technique was developed and implemented to recognise the distorted features of the 2D-patterned shape cuttings. To accommodate the geometrical pattern variations, the cutting paths of the 2D-patterned shapes were extracted using either the chain-coding technique or the binary morphological techniques.

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29

Deni, Mohd Salleh Mohd. "Vibrational anharmonicity and the elastic behaviour of some antiferromagnetic materials." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380942.

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30

Son, Seyul. "Nonlinear Electromechanical Deformation of Isotropic and Anisotropic Electro-Elastic Materials." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28587.

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Electro-active polymers (EAPs) have emerged as a new class of active materials, which produce large deformations in response to an electric stimulus. EAPs have attractive characteristics of being lightweight, inexpensive, stretchable, and flexible. Additionally, EAPs are conformable, and their properties can be tailored to satisfy a broad range of requirements. These advantages have enabled many target applications in actuation and sensing. A general constitutive formulation for isotropic and anisotropic electro-active materials is developed using continuum mechanics framework and invariant theory. Based on the constitutive law, electromechanical stability of the electro-elastic materials is investigated using convexity and polyconvexity conditions. Implementation of the electro-active material model into a commercial finite element software (ABAQUS 6.9.1, PAWTUCKET, RI, USA) is presented. Several boundary and initial value problems are solved to investigate the actuation and sensing response of isotropic and anisotropic dielectric elastomers (DEs) subject to combined mechanical and electrical loads. The numerical response is compared with experimental results to validate the theoretical model. For the constitutive formulation of the electro-elastic materials, invariants for the coupling between two families of electro-active fibers (or particles) and the applied electric field are introduced. The effect of the orientation of the electro-active fibers and the electric field on the electromechanical coupling is investigated under equibiaxial extension. Advantage of the constitutive formulation derived in this research is that the electromechanical coupling can be illustrated easily by choosing invariants for the deformation gradient tensor, the electro-active fibers, and the electric field. For the electromechanical stability, it is shown that the stability can be controlled by tuning the material properties and the orientation of the electro-active fibers. The electromechanical stability condition is useful to build a stable free energy function and prevent the instabilities (wrinkling and electric breakdown) for the electro-elastic materials. The invariant-based constitutive formulation for the electro-elastic materials including the isotropic and anisotropic DEs is implemented into a user subroutine (UMAT in ABAQUS: user defined material) by using multiplicative decomposition of the deformation gradient and the applicability of the UMAT is shown by simulating a complicated electromechanical coupling problem in ABAQUS/CAE. Additionally, the static and dynamic sensing and actuation response of tubular DE transducers (silicone and polyacrylate materials) with respect to combined electrical and mechanical stimuli is obtained experimentally. It is shown that the silicone samples have better dynamic and static sensing characteristics than the polyacrylate. The theoretical modeling accords well with the experimental results.
Ph. D.

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31

Mitchell, Kelsey Ryan. "Broadband Acoustic Liner Optimization Study Using Novel Poro-elastic Materials." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52947.

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With the continual challenges associated with reducing aircraft engine noise, there is need for acoustic liner configurations that target broadband performance. This thesis experimentally and analytically investigates passive noise control methods to improve broadband frequency attenuation through various acoustic liner designs. The inclusion of acoustic metamaterials within these liners is examined and optimized. The metamaterials studied consist of resonant and non-resonant materials which include porous foams, microperforated plates (MPP), and embedded aluminum masses. Through finite element analysis, the understanding of the physics behind acoustics as well as aeroacoustics inspire their design. Sensitivity studies on the overall liner shape, facesheet properties, poro-elastic material properties, MPP's, as well as size and placement of embedded masses assist in successfully achieving broadband attenuation. Within the finite element study, an optimization tool will provide additional assistance in quantifying critical system parameters within the designs by minimizing the sum of the transmitted sound intensity over the design frequency bandwidth and hence maximizing attenuation. Broadband frequency absorption and attenuation is successfully achieved within the frequency range of 400-2600 Hz through the design of a varying depth optimized acoustic liner as well as a metamaterial-inspired liner.
Master of Science

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32

Hsü, I.-Min. "Crack problems for elastic-plastic materials under antiplane shear loadings /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487598748017683.

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33

Kuninaka, Hiroto. "Theoretical and Numerical Studies of Inelastic Impacts of Elastic Materials." Kyoto University, 2004. http://hdl.handle.net/2433/147714.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第10955号
人博第242号
15||197(吉田南総合図書館)
新制||人||60(附属図書館)
UT51-2004-G802
京都大学大学院人間・環境学研究科人間・環境学専攻
(主査)教授冨田博之, 教授宮本嘉久, 助教授早川尚男, 助教授阪上雅昭
学位規則第4条第1項該当

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34

Zhen, Tiejun. "Compressive behavior of kinking nonlinear elastic solids - Ti3SiC2, graphite, mica and BN /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/312.

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35

Chen, Kwo-Shyong. "Hygrothermomechanical response investigations associated with elastic porous media /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487265555441632.

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36

Hegg, Meredith Michelle. "Exact Relations and Links for Fiber-Reinforced Elastic Composites." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/164322.

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Mathematics
Ph.D.
Predicting the effective elastic properties of a composite material based on the elastic properties of the constituent materials is extremely difficult, even when the microstructure is known. However, there are cases where certain properties in constituents always carry over to a composite, regardless of the microstructure of the composite. We call such instances exact relations. The general theory of exact relations allows us to find all of these instances in a wide variety of contexts including elasticity, conductivity, and piezoelectricity. We combine this theory with ideas from representation theory to find all exact relations for fiber-reinforced polycrystalline composites. We further extend these ideas to the concept of links. When two composites have the same microstructure but different constituent materials, their effective tensors may be related. We use the theory of exact relations to find such relations, which we call links. In this work we describe a special set of links between elasticity tensors of fiber-reinforced polycrystalline composites. These links allow us to generalize certain results from specific examples to generate new information about this widely-used class of composites. In particular, we apply the link to obtain information about composites made from two transversely isotropic materials and polycrystals made from one orthotropic material.
Temple University--Theses

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37

Hasegawa, Y., M. Shikida, and K. Sato. "Impact Resilience Measurement of Elastic Materials by using Active Tactile Sensor." IEEE, 2006. http://hdl.handle.net/2237/9542.

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38

Lee, Jae Sang. "Effective properties of three-phase electro-magneto-elastic multifunctional composite materials." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1448.

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Coupling between the electric field, magnetic field, and strain of composite materials is achieved when electro-elastic (piezoelectric) and magneto-elastic (piezomagnetic) particles are joined by an elastic matrix. Although the matrix is neither piezoelectric nor piezomagnetic, the strain field in the matrix couples the E field of the piezoelectric phase to the B field of the piezomagnetic phase. This three-phase electro-magneto-elastic composite should have greater ductility and formability than a two-phase composite in which E and B are coupled by directly bonding two ceramic materials with no compliant matrix. A finite element analysis and homogenization of a representative volume element is performed to determine the effective electric, magnetic, mechanical, and coupled-field properties of an elastic (epoxy) matrix reinforced with piezoelectric and piezomagnetic fibers as functions of the phase volume fractions, the fiber (or particle) shapes, the fiber arrangements in the unit cell, and the fiber material properties with special emphasis on the symmetry properties of the fibers and the poling directions of the piezoelectric and piezomagnetic fibers. The effective magnetoelectric moduli of this three-phase composite are, however, less than the effective magnetoelectric coefficients of a two-phase piezoelectric/piezomagnetic composite, because the epoxy matrix is not stiff enough to transfer significant strains between the piezomagnetic and piezoelectric fibers.

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39

Sun, Miao. "Optimal Recovery of Elastic Properties for Anisotropic Materials through Ultrasonic Measurements." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/SunM2002.pdf.

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40

Dowaikh, Mohammad Abdulghani. "Surface and interfacial waves and deformations in pre-stressed elastic materials." Thesis, Connect to e-thesis, 1990. http://theses.gla.ac.uk/709/.

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41

Harutyunyan, Satenik. "Magnetic and Elastic Interactions at Cracks and Interfaces in Ferromagnetic Materials." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29209.

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In addition to being useful for some nondestructive evaluation techniques, interactions between magnetic fields and defects in solids may also alter material properties. To explore this possibility, Maxwellâ s equations were coupled with a continuum mechanics model for elastic strain to formulate analytical expressions for the interaction of a magnetic field with several crack geometries. The influence of crack velocity and a realistic (nonlinear) magnetic susceptibility were included into a model of this type for the first time and shown to introduce unexpected trends in the magneto-elastic stress intensity. Singularities magneto-elastic stresses appear at different combinations of magnetic field strength and crack velocity, and the stresses at the crack tip switch sign. In a related study, the interaction of an alternating magnetic field with elastic stress through was explored through a coupling effect known as magneto-acoustic resonance. A model for the phenomena, in which magnetic waves excite elastic waves and vice versa, was formulated and used to explore the spin (magnon) and anti-plane elastic (phonon) interactions in piecewise homogeneous ferromagnetic spaces with two different sets of properties. The model suggests some combinations of magnetic field and frequency can produce a new kind of wave to appear. These new waves, which we call Accompanying Surface Magnetoelastic (ASM) waves, are localized at the interface between the two ferromagnetic media and they accompany reflection and transmission waves. It is shown that the amplitudes of the reflected, transmitted, and ASM waves depend strongly on magnetic field strength, frequency, and the angle of the incident wave, as well as on the physical properties of ferromagnetic media.
Ph. D.

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42

Jasim, Mahdi H. "Elastic and inelastic scattering of fast neutrons in fusion reactor materials." Thesis, Aston University, 1985. http://publications.aston.ac.uk/10594/.

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In this 'WOrk , the angular distributions for eTastic ·and. iBela:~ii.tc scattering of fast neutrons in fusion .reactor materials l'ia:~te<~ studied Lithium and wad material are- -likely' ';;i;"be ~n CCIUfX)nents of fusion reactor wall con£igut'atiQn qesign .. .We m=asurements were perfonnedusing an associated part;icl~,~~-; flight technique • The 14 and 14 .. 44 Mev neutrons were p~u¢ed 1;Jy. ;tli.$ T(d,n} 4He reaction with deut.erons Peinga<;eelerated in a 150kev SAME..S type Jaccelerator at ASTON and in.the 3. Mev ~~ at the Jo.i;nt Radiation. Centre I Birmingham I. res~vely; .. The q,ss.Qcj.a.~~ alpha-particles and fast. neu.tJ;qri$ Were; deteeteCl!. ~;¥.'~l :o£'·~·:p~a;§~¢; scintillator rrpunted on. a fa:st£GC1.Jsed photoroillmplj;er

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43

Wang, Yi. "Finite deformations of a generalized Blatz-Ko material." Thesis, University of Plymouth, 1996. http://hdl.handle.net/10026.1/2832.

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In this dissertation, the finite deformations of a certain class of compressible, isotropic elastic materials are investigated. The class is characterized by a two-parameter family of strain energy functions which includes the well-known Blatz-Ko material model for foam rubbers. The Blatz-Ko material, which has been arrived at by experiment and whose deformations have been studied previously, is obtained from the considered class of materials by specifying one of the two parameters involved in the definition of the class. On employing the semi-inverse method, according to which the form of the solution is given at the outset in terms of functions which are then determined from the equilibrium equations and boundary conditions, closed-form solutions to the equilibrium equations are obtained for the non-homogeneous deformations describing the straightening of a sector of a circular tube, the bending of a rectangular block into a sector of a circular tube, the eversion of cylindrical and spherical shells, and the cylindrical and spherical expansions, and a number of associated boundary value problems are investigated using both analytical and numerical methods. Certain situations in which solutions of the pre-assigned form cannot exist are identified and cases of non-uniqueness are dealt with by discriminating between the different solutions on physical grounds. The homogeneous deformations of the materials in this class are also examined and, throughout, comparison is being made with the behaviour of the Blatz-Ko material. For the whole range of deformations examined, it is found that the materials for which one of the parameters is greater than, or equal to, two (the case when this parameter equals to two corresponds to the Blatz-Ko material) become harder as this parameter increases, but that otherwise they all behave in a similar manner. Consequently, it is concluded that the materials in this particular subclass will also represent foam rubbers of the type described by the Blatz-Ko material. In order to describe the situations in which the solutions become unstable, the conditions for the strong ellipticity of the equilibrium equations for non-linearly elastic materials are reformulated so as to be expressible in terms of the derivatives of the strain-energy function regarded as a function of the principal stretches. Use of these conditions reveals that the solutions to the considered boundary value problems become unstable at certain critical values of the applied loads.

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44

Moore, Robert Hunter. "Elastic and time dependent matrix cracking in cross-ply composite laminates." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/63971.

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The effects of time and stress level were investigated in cross-ply laminates to gain more understanding on the damage events in composites. Analytical predictions of the effect of stress level were performed for the case of linear elastic materials. The predictions were based on energy methods and linear elastic fracture mechanics. Damage was simulated with a Monte Carlo numerical scheme. The predicted results corresponded well with experimental data in the literature. Experimental testing was performed on cross-ply laminates to gain a better understanding of the effect of time and rate on matrix cracking. The tests were performed on Kevlar/epoxy and graphite/epoxy [0/90₃]₈ laminates. The results indicate that the stress levels required for matrix cracking are a function of how fast the specimens were loaded. Also, significant time dependent damage was observed in cross-ply laminates which were subjected to sustained loads.
Master of Science

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45

Larsson, Ashley Ian. "Mathematical aspects of wave theory for inhomogeneous materials /." Title page, table of contents and summary only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phl334.pdf.

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46

Soediono, Andy H. "Near tip stress and strain fields for short elastic cracks." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19557.

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47

Evans, Benjamin Scott. "Model based techniques for use by automated systems handling non-rigid materials." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261355.

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48

Logan, Kathryn Vance. "Elastic-plastic behavior of hot pressed composite titanium diboride/alumina powders produced using self-propagating high temperature synthesis." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15853.

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49

KURAPATI, SIVA NAGA VENKATA RAVI KIRAN. "ELASTIC-PLASTIC INDENTATION DEFORMATION IN HOMOGENEOUS AND LAYERED MATERIALS: FINITE ELEMENT ANALYSIS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/576.

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The complex phenomenon of indentation deformation is studied using finite element analysis for both homogeneous and layered materials. For the homogeneous materials, the elastic-plastic deformation at large indentation depth is studied. The variation of the load-displacement curves as well as the variation of the energy ratio with the applied indentation depth for different strain hardening indices is presented. The power law relation between the indentation load and depth for shallow indentation becomes invalid for deep indentation. The ratio of plastic energy to total mechanical work is a linear function of the ratio of residual indentation depth and maximum indentation depth. For the layered materials (film-substrate systems), the elastic deformation under an indenter is studied. Various material parameters are investigated, including film thickness and modulus. A generalized power law equation is presented for characterizing the indentation load-displacement responses of film-substrate structures.

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50

Kurapati, Siva Naga Venkata Ravi Kiran. "Elastic-plastic indentation deformation in homogeneous and layered materials finite element analysis /." Lexington, Ky. : [University of Kentucky Libraries], 2009. http://hdl.handle.net/10225/992.

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Thesis (M.S.)--University of Kentucky, 2009.
Title from document title page (viewed on July 23, 2009). Document formatted into pages; contains: x, 114 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 102-113).

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Dissertations / Theses on the topic 'Elastic materials'

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