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1
Rashid, Asim. "Finite Element Modeling of Contact Problems." Doctoral thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-124572.
Повний текст джерелаАнотація:
Contact is the principal way load is transferred to a body. The study of stresses and deformations arising due to contact interaction of solid bodies is thus of paramount importance in many engineering applications. In this work, problems involving contact interactions are investigated using finite element modeling. In the first part, a new augmented Lagrangian multiplier method is implemented for the finite element solution of contact problems. In this method, a stabilizing term is added to avoid the instability associated with overconstraining the non-penetration condition. Numerical examples are presented to show the influence of stabilization term. Furthermore, dependence of error on different parameters is investigated. In the second part, a disc brake is investigated by modeling the disc in an Eulerian framework which requires significantly lower computational time than the more common Lagrangian framework. Thermal stresses in the brake disc are simulated for a single braking operation as well as for repeated braking. The results predict the presence of residual tensile stresses in the circumferential direction which may cause initiation of radial cracks on the disc surface after a few braking cycles. It is also shown that convex bending of the pad is the major cause of the contact pressure concentration in middle of the pad which results in the appearance of a hot band on the disc surface. A multi-objective optimization study is also performed, where the mass of the back plate, the brake energy and the maximum temperature generated on the disc surface during hard braking are optimized. The results indicate that a brake pad with lowest possible stiffness will result in an optimized solution with regards to all three objectives. Finally, an overview of disc brakes and related phenomena is presented in a literature review. In the third part, a lower limb donned in a prosthetic socket is investigated. The contact problem is solved between the socket and the limb while taking friction into consideration to determine the contact pressure and resultant internal stress-strain in the soft tissues. Internal mechanical conditions and interface stresses for three different socket designs are compared. Skin, fat, fascia, muscles, large blood vessels and bones are represented separately, which is novel in this work.
2
Bodur, Mehmet Ata. "Finite Element Analysis Of Discontinuous Contact Problems." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12606964/index.pdf.
Повний текст джерелаАнотація:
Contact is a phenomenon faced in every day life, which is actually a complex problem to tackle for engineers. Most of the times, may be impossible to get analytic or exact results for the interaction of bodies in contact.
In this thesis work, solution of the frictionless contact of an elastic body, touching to a rigid planar surface for two-dimensional elasticitynamely plane stress, plane strain and axi-symmetric formulations is aimed. The problem is solved numerically, with Finite Element Method, and an Object Oriented computer program in C++ for this purpose is written, and the results are verified with some basic analytic solutions and ABAQUS package program. It is not aimed in this thesis work to give a new solution in the area of solution of contact problems, but instead, it is aimed to form a strong basis, and computational library, which is extendible for further development of the subject to include friction, plasticity, and different material modeling in this advanced field of mechanics.
3
Liu, Shubin Carleton University Dissertation Engineering Aerospace. "Boundary element analysis in contact fracture mechanics." Ottawa, 1994.
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4
KATRAGADDA, SRIRAMAPRASAD. "FINITE ELEMENT ANALYSIS OF 3D CONTACT PROBLEMS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123812018.
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5
Im, Moon Hyuk. "Finite element analysis of frictional contact problems /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487598748017846.
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6
Nesemann, Leo [Verfasser]. "Finite element and boundary element methods for contact with adhesion / Leo Nesemann." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1013365542/34.
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7
Neto, Dorival Piedade. "Sobre estratégias de resolução numérica de problemas de contato." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14072009-165646/.
Повний текст джерелаАнотація:
Os problemas de contato representam uma classe de problemas da mecânica dos sólidos para a qual a não-linearidade é introduzida pela alteração das condições de contorno, as quais só podem ser determinadas no decorrer do processo de resolução. O presente trabalho trata dos problemas de contato abordando aspectos de sua formulação e implementação numérica. Apresentam-se, em particular, as formulações de dois diferentes tipos de elemento de contato revendo-se, mais detalhadamente, o tratamento numérico das restrições decorrentes de contato. Algumas estratégias para resolução computacional desta classe de problemas, consistindo em técnicas de otimização, foram implementadas num programa computacional de elementos finitos e avaliadas comparativamente por meio de exemplos numéricos com diferentes graus de complexidade.Contact problems represent a class of solid mechanics problems for which the nonlinear behavior is caused by the change of the boundary conditions during the solution process. The present work treats contact problems observing aspects of its formulation and numerical implementation. Specifically, the formulation for two different contact elements is presented, analyzing, in details, the numerical formulation that results from the contact. Some strategies for the computational solution of this class of problems, given by optimization techniques, were implemented in a finite element computational program and were compared and evaluated by numerical examples with different levels of complexity.
8
Pascoe, Steven Keith. "Contact stress analysis using the finite element method." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240266.
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9
Man, Kim Wai. "Boundary element analysis of contact in fracture mechanics." Thesis, University of Portsmouth, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317864.
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10
Eterovic, Adrian Luis. "Finite element analysis of large deformation contact problems." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13063.
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11
Motamedian, Hamid Reza. "Robust Formulations for Beam-to-Beam Contact." Licentiate thesis, KTH, Hållfasthetslära (Avd.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183980.
Повний текст джерелаАнотація:
Contact between beam elements is a specific category of contact problems which was introduced by Wriggers and Zavarise in 1997 for normal contact and later extended by Zavarise and Wriggers to include tangential and frictional contact. In these works, beam elements are assumed to have rigid circular cross-sections and each pair of elements cannot have more than one contact point. The method proposed in the early papers is based on introducing a gap function and calculating the incremental change of that gap function and its variation in terms of incremental change of the nodal displacement vector and its variation. Due to complexity of derivations, specially for tangential contact, it is assumed that beam elements have linear shape functions. Furthermore, moments at the contact point are ignored. In the work presented in this licentiate thesis, we mostly adress the questions of simplicity and robustness of implementations, which become critical once the number of contact is large. In the first paper, we have proposed a robust formulation for normal and tangential contact of beams in 3D space to be used with a penalty stiffness method. This formulation is based on the assumption that contact normal, tangents, and location are constant (independent of displacements) in each iteration, while they are updated between iterations. On the other hand, we have no restrictions on the shape functions of the underlying beam elements. This leads to a mathematically simpler derivation and equations, as the linearization of the variation of the gap function vanishes. The results from this formulation are verified and benchmarked through comparison with the results from the previous algorithms. The proposed method shows better convergence rates allowing for selecting larger loadsteps or broader ranges for penalty stiffness. The performance and robustness of the formulation is demonstrated through numerical examples. In the second paper, we have suggested two alternative methods to handle in-plane rotational contact between beam elements. The first method follows the method of linearizing the variation of gap function, originally proposed by Wriggers and Zavarise. To be able to do the calculations, we have assumed a linear shape function for the underlying beam elements. This method can be used with both penalty stiffness and Lagrange multiplier methods. In the second method, we have followed the same method that we used in our first paper, that is, using the assumption that the contact normal is independent of nodal displacements at each iteration, while it is updated between iterations. This method yields simpler equations and it has no limitations on the shape functions to be used for the beam elements, however, it is limited to penalty stiffness methods. Both methods show comparable convergence rates, performance and stability which is demonstrated through numerical examples.Kontakt mellan balkelement är en speciell typ av kontaktproblem som först analyserades 1997 av Wriggers och Zavarise med avseende på kontakt i normalriktningen. Teorin utvecklades senare av Zavarise och Wriggers och inkluderade då även kontakt i tangentiella riktningar. I dessa arbeten antas balkelementen ha ett styvt cirkulärt tvärsnitt och varje elementpar kan inte ha mer än en kontaktpunkt. Metodiken i dessa artiklar bygger på att en glipfunktion införs och därefter beräknas den inkrementella förändringen av glipfunktionen, och också dess variation, som funktion av den inkrementella förändringen av förskjutningsvektorn och dess variation. På grund av de komplicerade härledningar som resulterar, speciellt för den tangentiella kontakten, antas det att balkelementen har linjära formfunktioner. Dessutom tas ingen hänsyn till de moment som uppstår vid kontaktpunkten. I de arbeten som presenteras i denna licentiatavhandling har vi valt att inrikta oss mot frågeställningar kring enkla och robusta implementeringar, något som blir viktigt först när problemet innefattar ett stort antal kontakter. I den första artikeln i avhandlingen föreslår vi en robust formulering för normal och tangentiell kontakt mellan balkar i en 3D-rymd.Formuleringen bygger på en kostnadsmetod och på antagandet att kontaktens normal- och tangentriktning samt dess läge förblir detsamma (oberoende av förskjutning) under varje iteration. Dock uppdateras dessa storheter mellan varje iteration. Å andra sidan har inga begränsningar införts för formfunktionerna hos de underliggande balkelementen. Detta leder till en matematiskt enklare härledning samt enklare ekvationer, eftersom variationen hos glipfunktionen försvinner. Resultat framtagna med hjälp av denna formulering har verifierats och jämförts med motsvarande resultat givna av andra metoder. Den föreslagna metoden ger snabbare konvergens vilket ger möjlighet att använda större laststeg eller större omfång hos styvheten i kontaktpunkten (s.k. kostnadsstyrhet). Genom att lösa numeriska exempel påvisas prestanda och robusthet hos den föreslagna formuleringen. I den andra artikeln föreslår vi två alternativa metoder för att hantera rotationer i kontaktplanet hos balkelementen. I den första metoden linjäriseras glipfunktionen. Denna metod presenterades först av Wriggers och Zavarise. För att kunna genomföra beräkningarna ansattes linjära formfunktioner för balkelementen. Den här metoden kan användas både med kostnadsmetoder och metoder baserade på Lagrangemultiplikatorer. I den andra föreslagna metoden har vi valt att följa samma tillvägagångsätt som i vår första artikel. Detta betyder att vi antar att kontaktens normalriktning är oberoende av förskjutningarna under en iteration men uppdateras sedan mellan iterationerna. Detta tillvägagångsätt ger enklare ekvationer och har inga begränsningar vad gäller de formfunktioner som används i balkelementen. Dock är metoden begränsad till att utnyttja kostnadsmetoder. Båda de föreslagna metoderna i denna artikel ger jämförbar konvergens, prestanda och stabilitet vilket påvisas genom att lösningar till olika numeriska exempel presenteras.
QC 20160408
12
Duan, FangFang. "Numerical tribology of the wheel-rail contact : Application to corrugation defect." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0019/document.
Повний текст джерелаАнотація:
Depuis plus d'un siècle, l’usure ondulatoire représente un des problèmes de maintenance les plus important pour les réseaux ferroviaires. Celle-ci est à l’origine d’émissions sonores incommodantes pour le voisinage et de vibrations structurelles pouvant réduire la durée de vie des infrastructures et matériels ferroviaires. Ce phénomène périodique présent à la surface des rails est intimement lié à la dynamique du contact roue-rail qui résulte des paramètres régissant le frottement, la dynamique du train et de la voie… Afin de mieux appréhender les conditions menant à l’apparition de l’usure ondulation, un modèle numérique a été proposé pour compenser l’impossibilité d’instrumenter localement et de façon fiable un contact roue-rail dynamiquement. Tout d'abord, un outil approprié a été choisi pour modéliser la dynamique du contact roue-rail afin de reproduire numérique de l’usure ondulatoire des voies rectilignes. Le code d'éléments finis dynamique implicite Abaqus a été choisi pour instrumenter numériquement localement le contact roue-rail. Ainsi, tant l'origine que l'évolution de l’usure ondulatoire dans des phases transitoires (accélération / décélération) sont étudiées. Une étude de sensibilité a été menée pour mettre en évidence la sensibilité de l’usure ondulatoire apparaissant dans des conditions transitoires au passage d’une ou plusieurs roues ainsi que d’un défaut géométrique présent à la surface du rail. Des conditions dynamiques locales d’adhérence-glissement (stick-slip), liées à la dynamique de la roue et du rail couplés par le contact, est identifié comme origine de l’usure ondulatoire des voies rectilignes dans des conditions transitoires. Deuxièmement, les résultats obtenues avec le modèles précédent ont mis en évidence une décroissance de l’amplitude de l’usure ondulatoire reproduire numérique en fonction du nombre de roue passant sur le rail. Ce résultat semble être en contradiction avec les observations de rails réels. Ce problème est lié à la difficulté de gérer la dynamique de contact, et tout particulièrement dans le cas où il y a des impacts locaux, dans les modèles éléments finis classiques tels que ceux implémentés dans Abaqus. Pour palier ce problème, une méthode de masser redistribuée a été implémentée dans Abaqus et utilisée sur le cas précédent. Les résultats montrent un accroissement plus réaliste de l’usure ondulatoire en fonction du nombre de rouesFor more than a century, rail corrugation has been exposed as one of the most serious problems experienced in railway networks. It also comes with a series of problems for maintenance, such as rolling noises and structural vibrations that can reduce lifetime of both train and track. This periodical phenomenon on rail surface is closely linked to wheel-rail contact dynamic, which depends on friction, train dynamics… To better understand corrugation birth conditions, a numerical model is suggested to complement the experimental limitations and to instrument a wheel-rail contact both locally and dynamically. At first, an appropriate tool was chosen to create the dynamic wheel-rail contact model to reproduce straight-track corrugation, also called “short-pitch” corrugation. The implicit dynamic finite element code Abaqus was chosen to investigate the dynamic local contact conditions. Both the origin and the evolution of straight-track corrugation under transient conditions (acceleration / deceleration) are studied. The parametrical sensibility of corrugation is thus investigated both with single/multiple wheel passing(s) and with geometric defect. A stick-slip phenomenon, linked to both wheel and rail dynamics coupled through the contact, is identified as the root of straight-track corrugation under transient conditions. Secondly, results obtained with the previous model have highlighted a quick decrease of corrugation amplitude with the increase of wheel passings over the rail. This last result seems to be in contradiction with reality. This problem comes from the difficulty to reliably manage contact dynamics, and particularly with local impacts, with the use of classical finite element models such as the one implemented in Abaqus. To compensate for this lack, a mass redistribution method is implemented in Abaqus and used with the previous case. The results show a more realistic corrugation growth according to the number of wheel passings
13
Tvedt, Kristofer Eugene 1963. "Determination of contact stress using gap finite element method." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278152.
Повний текст джерелаАнотація:
The gap finite element uses the Richard equation to account for the nonlinearity in the boundary condition changes during deformation. This is accomplished by replacing the boundary nonlinearity with an equivalent material nonlinearity within the finite element program and using an incremental solution method. The gap element is developed as a special element with easily obtainable input parameters. The gap element is used to predict high stresses in local areas related to the contact of structural bodies. The major advantage to using a finite element solution with a gap element over a classical solution is in the ease of combining the contact stress with other stresses in a structural body.
14
Jinn, Jong-Tae. "Finite element analysis of elastic contact problems with friction /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487668215807717.
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15
Leahy, John C. "Three-dimensional frictional contact analysis using the Boundary Element Method." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263491.
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16
KEUM, BANGYONG. "ANALYSIS OF 3-D CONTACT MECHANICS PROBLEMS BY THE FINITE ELEMENT AND BOUNDARY ELEMENT METHODS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1054815631.
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17
Zhang, Jiaqi. "Finite-element simulations of interfacial flows with moving contact lines." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99058.
Повний текст джерелаАнотація:
In this work, we develop an interface-preserving level-set method in the finite-element framework for interfacial flows with moving contact lines. In our method, the contact line is
advected naturally by the flow field. Contact angle hysteresis can be easily implemented
without explicit calculation of the contact angle or the contact line velocity, and meshindependent results can be obtained following a simple computational strategy. We have
implemented the method in three dimensions and provide numerical studies that compare
well with analytical solutions to verify our algorithm.
We first develop a high-order numerical method for interface-preserving level-set reinitialization. Within the interface cells, the gradient of the level set function is determined by a
weighted local projection scheme and the missing additive constant is determined such that
the position of the zero level set is preserved. For the non-interface cells, we compute the
gradient of the level set function by solving a Hamilton-Jacobi equation as a conservation
law system using the discontinuous Galerkin method. This follows the work by Hu and Shu
[SIAM J. Sci. Comput. 21 (1999) 660-690]. The missing constant for these cells is recovered
using the continuity of the level set function while taking into account the characteristics. To
treat highly distorted initial conditions, we develop a hybrid numerical flux that combines
the Lax-Friedrichs flux and a penalty flux. Our method is accurate for non-trivial test cases
and handles singularities away from the interface very well. When derivative singularitiesare present on the interface, a second-derivative limiter is designed to suppress the oscillations. At least (N + 1)th order accuracy in the interface cells and Nth order accuracy in
the whole domain are observed for smooth solutions when Nth degree polynomials are used.
Two dimensional test cases are presented to demonstrate superior properties such as accuracy, long-term stability, interface-preserving capability, and easy treatment of contact lines.
We then develop a level-set method in the finite-element framework. The contact line singularity is removed by the slip boundary condition proposed by Ren and E [Phys. Fluids, vol.
19, p. 022101, 2007], which has two friction coefficients: βN that controls the slip between
the bulk fluids and the solid wall and βCL that controls the deviation of the microscopic
dynamic contact angle from the static one. The predicted contact line dynamics from our
method matches the Cox theory very well. We further find that the same slip length in
the Cox theory can be reproduced by different combinations of (βN; βCL). This combination leads to a computational strategy for mesh-independent results that can match the
experiments. There is no need to impose the contact angle condition geometrically, and the
dynamic contact angle automatically emerges as part of the numerical solution. With a little
modification, our method can also be used to compute contact angle hysteresis, where the
tendency of contact line motion is readily available from the level-set function. Different test
cases, including code validation and mesh-convergence study, are provided to demonstrate
the efficiency and capability of our method.
Lastly, we extend our method to three-dimensional simulations, where an extension equation
is solved on the wall boundary to obtain the boundary condition for level-set reinitializaiton
with contact lines. Reinitialization of ellipsoidal interfaces is presented to show the accuracy and stability of our method. In addition, simulations of a drop on an inclined wall are
presented that are in agreement with theoretical results.Doctor of Philosophy
When a liquid droplet is sliding along a solid surface, a moving contact line is formed at the intersection of the three phases: liquid, air and solid. This work develops a numerical method to study problems with moving contact lines. The partial differential equations describing the problem are solved by finite element methods. Our numerical method is validated against experiments and theories. Furthermore, we have implemented our method in three-dimensional problems.
18
Oysu, Cuneyt. "Coupled finite and boundary element analysis of elastoplastic contact problems." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391437.
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19
Liu, Ming. "FINITE ELEMENT ANALYSIS OF THE CONTACT DEFORMATION OF PIEZOELECTRIC MATERIALS." UKnowledge, 2012. http://uknowledge.uky.edu/cme_etds/15.
Повний текст джерелаАнотація:
Piezoelectric materials in the forms of both bulk and thin-film have been widely used as actuators and sensors due to their electromechanical coupling. The characterization of piezoelectric materials plays an important role in determining device performance and reliability. Instrumented indentation is a promising method for probing mechanical as well as electrical properties of piezoelectric materials.
The use of instrumented indentation to characterize the properties of piezoelectric materials requires analytical relations. Finite element methods are used to analyze the indentation of piezoelectric materials under different mechanical and electrical boundary conditions.
For indentation of a piezoelectric half space, a three-dimensional finite element model is used due to the anisotropy and geometric nonlinearity. The analysis is focused on the effect of angle between poling direction and indentation-loading direction on indentation responses.
For the indentation by a flat-ended cylindrical indenter, both insulating indenter and conducting indenter without a prescribed electric potential are considered. The results reveal that both the indentation load and the magnitude of the indentation-induced potential at the contact center increase linearly with the indentation depth.
For the indentation by an insulating Berkovich indenter, both frictionless and frictional contact between the indenter and indented surface are considered. The results show the indentation load is proportional to the square of the indentation depth, while the indentation-induced potential at the contact center is proportional to the indentation depth.
Spherical indentation of piezoelectric thin films is analyzed in an axisymmetric finite element model, in which the poling direction is anti-parallel to the indentation-loading direction.
Six different combinations of electrical boundary conditions are considered for a thin film perfectly bonded to a rigid substrate under the condition of the contact radius being much larger than the film thickness. The indentation load is found to be proportional to the square of the indentation depth.
To analyze the decohesion problem between a piezoelectric film and an elastic substrate, a traction-separation law is used to control the interfacial behavior between a thin film and an electrically grounded elastic substrate. The discontinuous responses at the initiation of interfacial decohesion are found to depend on interface and substrate properties.
20
Pierce, Timothy G. "A parallel algorithm for contact in a finite element hydrocode /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
Повний текст джерела
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Lawson, A. R. "Finite element modelling of blunt or non-contact head injuries." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/10749.
Повний текст джерелаАнотація:
Safety is an increasingly important aspect of vehicle design. Legislation
requires minimum levels of safety through full scale tests. Customers are provided with
information regarding the safety performance of vehicles so that they can make an
informed buying decision. Vehicle crashes were responsible for 40000 fatalities and 5.2
million non fatally injured patients in the US during 1994. The direct and direct cost of
head injuries in the US is estimated at $25 billion per year. Injury criteria that can
predict the severity of head injuries are important engineering tools for improving
vehicle safety.
At present the injury that the human head is subjected to is predicted by the
Head Injury Criterion (HIC). This criterion is inadequate as it is not based upon a
thorough understanding of the underlying head injury mechanisms.
The important blunt or non-contact head injury mechanisms are diffuse axonal
injury, bridging vein disruption and surface contact contusions. The severity of these
injury mechanisms is hypothesised to be related to the level of motion of the brain with
respect to the skull.
Finite element modelling is used to analyse these head injury mechanisms.
Models are developed which include all the relevant anatomical entities and detail.
Accurate material property information and boundary conditions are used in the
modelling to ensure that the head injury mechanisms can be accurately simulated.
Tissue failure criteria are developed to link the various field parameters
monitored during the simulations with injury severity. The models are then
comprehensively validated with information obtained from pathological observations,
cadaver experiments, accident reconstructions and volunteer data.
These models are then used to determine the biomechanics of head injury and
to develop improved head injury tolerance curves. The simulations demonstrate that
head injury severity is dependent upon the magnitude, pulse duration and direction of
the applied translational and rotational acceleration pulses.
22
Lawson, Anthony Richard. "Finite element modelling of blunt or non-contact head injuries." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/10749.
Повний текст джерелаАнотація:
Safety is an increasingly important aspect of vehicle design. Legislation requires minimum levels of safety through full scale tests. Customers are provided with information regarding the safety performance of vehicles so that they can make an informed buying decision. Vehicle crashes were responsible for 40000 fatalities and 5.2 million non fatally injured patients in the US during 1994. The direct and direct cost of head injuries in the US is estimated at $25 billion per year. Injury criteria that can predict the severity of head injuries are important engineering tools for improving vehicle safety. At present the injury that the human head is subjected to is predicted by the Head Injury Criterion (HIC). This criterion is inadequate as it is not based upon a thorough understanding of the underlying head injury mechanisms. The important blunt or non-contact head injury mechanisms are diffuse axonal injury, bridging vein disruption and surface contact contusions. The severity of these injury mechanisms is hypothesised to be related to the level of motion of the brain with respect to the skull. Finite element modelling is used to analyse these head injury mechanisms. Models are developed which include all the relevant anatomical entities and detail. Accurate material property information and boundary conditions are used in the modelling to ensure that the head injury mechanisms can be accurately simulated. Tissue failure criteria are developed to link the various field parameters monitored during the simulations with injury severity. The models are then comprehensively validated with information obtained from pathological observations, cadaver experiments, accident reconstructions and volunteer data. These models are then used to determine the biomechanics of head injury and to develop improved head injury tolerance curves. The simulations demonstrate that head injury severity is dependent upon the magnitude, pulse duration and direction of the applied translational and rotational acceleration pulses.
23
Navarro, Jiménez José Manuel. "Contact problem modelling using the Cartesian grid Finite Element Method." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/124348.
Повний текст джерелаАнотація:
[ES] La interacción de contacto entre sólidos deformables es uno de los fenómenos más complejos en el ámbito de la mecánica computacional. La resolución de este problema requiere de algoritmos robustos para el tratamiento de no linealidades geométricas. El Método de Elementos Finitos (MEF) es uno de los más utilizados para el diseño de componentes mecánicos, incluyendo la solución de problemas de contacto. En este método el coste asociado al proceso de discretización (generación de malla) está directamente vinculado a la definición del contorno a modelar, lo cual dificulta la introducción en la simulación de superficies complejas, como las superficies NURBS, cada vez más utilizadas en el diseño de componentes.
Esta tesis está basada en el "Cartesian grid Finite Element Method" (cgFEM). En esta metodología, encuadrada en la categoría de métodos "Immersed Boundary", se extiende el problema a un dominio de aproximación (cuyo mallado es sencillo de generar) que contiene al dominio de análisis completamente en su interior. Al desvincular la discretización de la definición del contorno del problema se reduce drásticamente el coste de generación de malla. Es por ello que el método cgFEM es una herramienta adecuada para la resolución de problemas en los que es necesario modificar la geometría múltiples veces, como el problema de optimización de forma o la simulación de desgaste.
El método cgFEM permite también crear de manera automática y eficiente modelos de Elementos Finitos a partir de imágenes médicas. La introducción de restricciones de contacto habilitaría la posibilidad de considerar los diferentes estados de integración implante-tejido en procesos de optimización personalizada de implantes.
Así, en esta tesis se desarrolla una formulación para resolver problemas de contacto 3D con el método cgFEM, considerando tanto modelos de contacto sin fricción como problemas con rozamiento de Coulomb. La ausencia de nodos en el contorno en cgFEM impide la aplicación de métodos tradicionales para imponer las restricciones de contacto, por lo que se ha desarrollado una formulación estabilizada que hace uso de un campo de tensiones recuperado para asegurar la estabilidad del método. Para una mayor precisión de la solución, se ha introducido la definición analítica de las superficies en contacto en la formulación propuesta.
Además, se propone la mejora de la robustez de la metodología cgFEM en dos aspectos: el control del mal condicionamiento del problema numérico mediante un método estabilizado, y la mejora del campo de tensiones recuperado, utilizado en el proceso de estimación de error.
La metodología propuesta se ha validado a través de diversos ejemplos numéricos presentados en la tesis, mostrando el gran potencial de cgFEM en este tipo de problemas.[CAT] La interacció de contacte entre sòlids deformables és un dels fenòmens més complexos en l'àmbit de la mecànica computacional. La resolució d'este problema requerix d'algoritmes robustos per al tractament de no linealitats geomètriques. El Mètode dels Elements Finits (MEF) és un dels més utilitzats per al disseny de components mecànics, incloent la solució de problemes de contacte. En este mètode el cost associat al procés de discretització (generació de malla) està directament vinculat a la definició del contorn a modelar, la qual cosa dificulta la introducció en la simulació de superfícies complexes, com les superfícies NURBS, cada vegada més utilitzades en el disseny de components. Esta tesi està basada en el "Cartesian grid Finite Element Method" (cgFEM). En esta metodologia, enquadrada en la categoria de mètodes "Immersed Boundary", s'estén el problema a un domini d'aproximació (el mallat del qual és senzill de generar) que conté al domini d'anàlisi completament en el seu interior. Al desvincular la discretització de la definició del contorn del problema es reduïx dràsticament el cost de generació de malla. És per això que el mètode cgFEM és una ferramenta adequada per a la resolució de problemes en què és necessari modificar la geometria múltiples vegades, com el problema d'optimització de forma o la simulació de desgast. El mètode cgFEM permet també crear de manera automàtica i eficient models d'Elements Finits a partir d'imatges mèdiques. La introducció de restriccions de contacte habilitaria la possibilitat de considerar els diferents estats d'integració implant-teixit en processos d'optimització personalitzada d'implants. Així, en esta tesi es desenvolupa una formulació per a resoldre problemes de contacte 3D amb el mètode cgFEM, considerant tant models de contacte sense fricció com a problemes amb fregament de Coulomb. L'absència de nodes en el contorn en cgFEM impedix l'aplicació de mètodes tradicionals per a imposar les restriccions de contacte, per la qual cosa s'ha desenvolupat una formulació estabilitzada que fa ús d'un camp de tensions recuperat per a assegurar l'estabilitat del mètode. Per a una millor precisió de la solució, s'ha introduït la definició analítica de les superfícies en contacte en la formulació proposada. A més, es proposa la millora de la robustesa de la metodologia cgFEM en dos aspectes: el control del mal condicionament del problema numèric per mitjà d'un mètode estabilitzat, i la millora del camp de tensions recuperat, utilitzat en el procés d'estimació d'error. La metodologia proposada s'ha validat a través de diversos exemples numèrics presentats en la tesi, mostrant el gran potencial de cgFEM en este tipus de problemes.
[EN] The contact interaction between elastic solids is one of the most complex phenomena in the computational mechanics research field. The solution of such problem requires robust algorithms to treat the geometrical non-linearities characteristic of the contact constrains. The Finite Element Method (FE) has become one of the most popular options for the mechanical components design, including the solution of contact problems. In this method the computational cost of the generation of the discretization (mesh generation) is directly related to the complexity of the analysis domain, namely its boundary. This complicates the introduction in the numerical simulations of complex surfaces (for example NURBS), which are being increasingly used in the CAD industry. This thesis is grounded on the Cartesian grid Finite Element Method (cgFEM). In this methodology, which belongs to the family of Immersed Boundary methods, the problem at hand is extended to an approximation domain which completely embeds the analysis domain, and its meshing is straightforward. The decoupling of the boundary definition and the discretization mesh results in a great reduction of the mesh generation's computational cost. Is for this reason that the cgFEM is a suitable tool for the solution of problems that require multiple geometry modifications, such as shape optimization problems or wear simulations. The cgFEM is also capable of automatically generating FE models from medical images without the intermediate step of generating CAD entities. The introduction of the contact interaction would open the possibility to consider different states of the union between implant and living tissue for the design of optimized implants, even in a patient-specific process. Hence, in this thesis a formulation for solving 3D contact problems with the cgFEM is presented, considering both frictionless and Coulomb's friction problems. The absence of nodes along the boundary in cgFEM prevents the enforcement of the contact constrains using the standard procedures. Thus, we develop a stabilized formulation that makes use of a recovered stress field, which ensures the stability of the method. The analytical definition of the contact surfaces (by means of NURBS) has been included in the proposed formulation in order to increase the accuracy of the solution. In addition, the robustness of the cgFEM methodology is increased in this thesis in two different aspects: the control of the numerical problem's ill-conditioning by means of a stabilized method, and the enhancement of the stress recovered field, which is used in the error estimation procedure. The proposed methodology has been validated through several numerical examples, showing the great potential of the cgFEM in these type of problems.
Navarro Jiménez, JM. (2019). Contact problem modelling using the Cartesian grid Finite Element Method [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124348
TESIS
24
Peng, Bo. "Discrete Element Method (DEM) Contact Models Applied to Pavement Simulation." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50399.
Повний текст джерелаАнотація:
Pavement is usually composed of aggregate, asphalt binder, and air voids; rigid pavement is built with hydraulic cement concrete; reinforced pavement contains steel. With these wide ranges of materials, different mechanical behaviors need to be defined in the pavement simulation. But so far, there is no research providing a comprehensive introduction and comparison between various contact models. This paper will give a detail exploration on the contact models that can be potentially used in DEM pavement simulation; in the analysis, it includes both a theoretical part, simulation results and computational time cost, which can reveal the fundamental mechanical behaviors for the models, and that can be a reference for researchers to choose a proper contact model. A new contact model—the power law viscoelastic contact model is implemented into software PFC 3D and is numerically verified. Unlike existing linear viscoelastic contact models, the approach presented in this thesis provides a detailed exploration of the contact model for thin film power-law creeping materials based on C.Y Chueng's work. This model is aimed at simulating the thin film asphalt layer between two aggregates, which is a common structure in asphalt mixtures. Experiments with specimens containing a thin film asphalt between two aggregates are employed to validate the new contact model.Master of Science
25
Masouros, Spyridon. "Articular contact in the knee joint : a finite element study." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/11484.
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26
Li, Yawei. "Dynamic prognostics of rolling element bearing condition." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15847.
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Liu, Gavin Chunye. "Vibration analysis of a thin moving web and its finite element implementation /." Online version of thesis, 1992. http://hdl.handle.net/1850/10698.
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Williams, Tracy Denise. "Remote condition monitoring of rolling element bearings with natural crack development." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17243.
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Zhuang, Shoubing. "Enhancing Implicit Finite Element Sheet Forming Simulation." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1206124132.
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30
English, Russell Gary. "Lagrange multiplier method for contact and friction : implementation and theory." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357426.
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Takahashi, S. "Stress analysis of elastic contact problems by the boundary element method." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233460.
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Lee, Kisu. "Numerical solution of elastic contact problems including friction /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487260531957279.
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GIRAUDON, GUILLOTEAU ISABELLE. "Modelisation du contact en dynamique : construction d'un element simplifie de contact et application a l'interaction rotor/stator." Nantes, 1999. http://www.theses.fr/1999NANT2076.
Повний текст джерелаАнотація:
La modelisation de l'interaction entre un rotor et un stator dans un moteur d'avion est tres delicate. Elle fait intervenir de nombreuses notions, comme le phenomene non-lineaire de contact, la dynamique, les grandes rotations notre etude a consiste a elaborer un element de contact et a l'integrer dans le module dynamique mecano du logiciel samcef, a l'aide de l'element utilisateur. Le schema d'integration temporelle du module transitoire mecano est le schema implicite de newmark. L'element simplifie de contact consiste en un ressort bilineaire dont la raideur est deduite d'une analyse en dynamique de la methode des multiplicateurs de lagrange. Cette raideur, associee a une methode classique des penalites, est tout d'abord utilisee pour modeliser le contact entre deux corps dans differents cas d'impact (masses ponctuelles, barres elastiques). Cette premiere serie de calculs, associee a une etude de compatibilite des vitesses et accelerations, a permis de degager des regles de choix des parametres de newmark. Puis, une seconde serie de calculs a ete realisee pour modeliser l'interaction entre un rotor et un stator apparue a la suite d'une perte d'aube de soufflante, dans la partie basse pression d'un moteur d'avion. Le phenomene etudie est le comportement de la structure sous l'effet du balourd cree par cette perte d'aube. Les modelisations sont realisees a l'aide de matrices gyroscopiques, evitant ainsi la gestion des grandes rotations. L'utilisation de la condensation dynamique pour les differentes parties du stator diminue le nombre de degres de liberte du modele et contribue a accelerer les calculs. Les resultats issus de mecano sont ensuite compares a ceux obtenus a l'aide d'un code commercial dedie a la simulation en dynamique rapide, ls-dyna3d, et possedant un puissant algorithme de recherche et de traitement du contact. Le nouvel element de contact s'avere etre un bon compromis entre precision et temps de calcul.
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Har, Jason. "A new scalable parallel finite element approach for contact-impact problems." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17080.
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Golan, Lawrence P. "Thermal analysis of sliding contact systems using the boundary element method." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-11242009-020117/.
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Maslan, Mohamad Haidir. "Development of predictive finite element models for complete contact fretting fatigue." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/development-of-predictive-finite-element-models-for-complete-contact-fretting-fatigue(a4652a74-7429-4f2c-b022-578111608651).html.
Повний текст джерелаАнотація:
Nucleation and propagation of cracks under fretting conditions has been a subject of study for many years. An extensive experimental investigation to study these cracks was undertaken by Royal Aerospace Establishment (RAE Farnborough). Of particular interest to RAE was an Aluminium alloy (L65) developed for aerospace applications. Many researchers have studied fretting damage and fatigue cracks. Some have examined damage development due to wear, whilst others have analysed cracks under linear elastic fracture mechanics (LEFM) domain. To date, no attempt has been made to develop an integrated numerical model which incorporates all aspects of fretting fatigue i.e. nucleation, initial (or early) crack growth, and long crack propagation. The development of such a model is the principal aim of this work. It is expected that the integrated approach will provide the basis for a standard fretting fatigue analysis of other materials, components, and structures using the finite element method (FEM).This study uses the earlier experimental results with RAE as the reference for comparison. The approach followed is to implement the various stages of fretting in a commercial finite element code, ABAQUS. Unlike previously used simple FE models, both specimen (Aluminium alloy) and the fretting pad (steel) are modelled to simulate the real contact conditions including slip. Various predictive models for crack nucleation (based on damage) and propagation (based on fracture mechanics) are developed, tested, and implemented in ABAQUS. Results clearly show that these models together provide a good estimation tool for predicting total life in complete contact fretting fatigue. It is envisaged that the integrated model will be easily utilised for other materials, components, and structures subjected to fretting fatigue conditions with minimum experimental testing required.
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Du, Huifeng. "Finite element analysis of adhesive contact interface in continuous 3D printing." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127164.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 65-68).
Projection Micro-Stereolithography (P[mu]SLA) is one of the most high-throughput additive manufacturing methods, yet preserving the high-resolution characteristic of light-based polymerization techniques. However, further improvement of fabrication speed and precision is usually hindered by the undesired adhesive forces at the curing interface, which is an inevitable consequence of in situ liquid-to-solid phase transition. To overcome this limitation, a bio-inspired super low adhesive interface has been proposed based on the observation of a slippery water layer on the peristome surface of pitcher plant. This hydrophobic layer provides an effective shield to solid adhesion due to its low adhesive energy, and attracting force between fabricated part and UV curing interface is significantly reduced. The introduction of this new lubrication layer not only remarkably improves the fabrication speed, but also increases the refilling rate of liquid pre-polymer resin.
This ultra-low adhesive interface shows promises for pushing the boundaries of continuous 3D printing into a realm of high-throughput additive manufacturing methods ready for industrial applications. In this thesis, I sought to provide a more comprehensive understanding of the solid-solid interaction at the curing interface of 3D photo-polymerizing systems. The state-of- the-art review of current literature suggested that a surface-based cohesive contact theory from a continuum mechanics perspective was the most appropriate model to establish a connection between interfacial material properties and macroscopic measurement results from experiment. Based on that I analyzed the entire mechanical separation process using finite-element method, and provided a semi-quantitative explanation of the stability of such lubricant-infused nano-cavities against peeling forces.
This research lays the ground for elucidating the physical mechanism behind the general adhesion-separation problem, and framework has been constructed in a more general form to allow for analyzing a wide range of interdisciplinary problems involving the dynamics of anisotropic moving contact lines and the propagation of surface instabilities induced by adhesive contact.
by Huifeng Du.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Mathews, Vayalat Thomas. "Tire Contact Patch Characterization through Finite Element Modeling and Experimental Testing." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/82708.
Повний текст джерелаАнотація:
The objective of this research is to provide an in-depth analysis of the contact patch behavior of a specific passenger car tire. A Michelin P205/60R15 tire was used for this study. Understanding the way the tire interacts with the road at various loads, inflation pressures and driving conditions is essential to optimizing tire and vehicle performance. The footprint shape and stress distribution pattern are very important factors that go into assessing the tire's rate of wear, the vehicle's fuel economy and has a major effect on the vehicle stability and control, especially under severe maneuvers.
In order to study the contact patch phenomena and analyze these stresses more closely, a finite element (FE) tire model which includes detailed tread pattern geometry has been developed, using a novel reverse engineering process. In order to validate this model, an experimental process has been developed to obtain the footprint shape and contact pressure distribution. The differences between the experimental and the simulation results are discussed and compared. The validated finite element model is then used for predicting the 3D stress distribution fields at the contact patch. The predictive capabilities of the finite element tire model are also explored in order to predict the handling characteristics of the test tire under different maneuvers such as pure cornering and pure braking.Master of Science
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Dawkins, Jeremy James. "Influence of crystallographic orientation in normal and sliding contacts." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24713.
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Himebaugh, Anne Katherine. "Finite Element Analysis of Insulated Railroad Joints." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/36159.
Повний текст джерелаАнотація:
In recent years, the lifetime of an insulated railroad joint in the field has decreased due to increasing wheel loads. The goal of this research is to investigate possible changes in insulated rail joint design in order to improve the performance of the insulated joint. The finite element program ABAQUS is used to model the supported butt joint. In this model, the rail, joint bars, epoxy, and ties surrounding the joint are modeled using solid elements. The remaining ties are modeled as an elastic foundation. The rail is subjected to a tensile load, as well as a vertical wheel load that is applied to the rail using Hertz contact theory.
Parametric studies are performed by varying the tie width, joint bar length, and joint bar dimensions. Two different wheel load locations are also investigated: centered about the end post, and halfway between the tie under the end post and the tie just to the left of the end post.
The vertical displacement of the rail and insulated joint is one measure used to determine the effect of the parameters on the insulated joint. However, since the most common cause of failure in insulated rail joints is the debonding of the epoxy, this research also focuses on the stresses present in the epoxy when the joint is subjected to a static wheel load. The two out-of-plane shear stresses as well as the normal peel stress are used to compare the various designs of the joint.Master of Science
41
Wiedemann, Sebastian. "Adaptive finite elements for a contact problem in elastoplasticity with Lagrange techniques." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2013. http://dx.doi.org/10.18452/16695.
Повний текст джерелаАнотація:
Das Thema dieser Dissertation ist die Herleitung und numerische Analyse von finiten Elementen für ein Problem in der Elastoplastizität mit Kontaktbedingungen. Die hergeleiteten finite Elemente Verfahren basieren auf einer Formulierung als Sattelpunktproblem und der Nutzung von Polynomen höherer Ordnung. Die Analyse der vorgestellten Verfahren beginnt mit dem Zeigen der Wohldefiniertheit und der Konvergenz. Im nächsten Schritt werden a priori Abschätzungen der Konvergenzraten gezeigt. Weiterhin führt die Einführung von Lagrange Multiplikatoren zu einem einheitlichen Ansatz zur a posteriori Abschätzung des Diskretisierungfehlers unter der Verwendung von Elementen höherer Ordnung. Zusätzlich ermöglicht es der Zugang über Lagrange Multiplikatoren die Äquivalenz der Diskretisierungsfehler in den Spannungen und in den Energien für finite Elemente niederer Ordnung zu zeigen, was insbesondere neu für Viereckselemente ist. Diese Äquivalenz wiederum erlaubt nun den Beweis der Konvergenz von adaptiven finiten Elementen niederer Ordnung. Für Dreieckselemente wird sogar die optimale Konvergenz bewiesen. Die theoretischen Erkenntnisse werden durch numerische Experimente bestätigt.The topic of this thesis is the derivation and analysis of some finite element schemes for a contact problem in elastoplasticity. These schemes are based on the formulation of the models as saddle point problems and use finite element spaces of arbitrary polynomial degrees. In this thesis, these new approaches with higher-order finite elements are shown to be well defined and convergent. Moreover, some a~priori estimates on the rates of convergences are proven. The use of Lagrange multipliers in the saddle point formulation yields a coherent approach to reliable a~posteriori error estimates for the proposed higher-order schemes. Additionally, the Lagrange multipliers are used to show the equivalence of the errors of the stresses and the energies, for low order finite elements using triangular or quadrilateral cells. For the first time, this allows for a proof of convergence for quadrilateral-based adaptive finite elements. Furthermore, the approach based on triangular cells is shown to be of optimal convergence. The theoretical findings are confirmed by numerical experiments.
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Hack, Roy Stuart. "The boundary element method applied to practical two-dimensional frictional contact problems." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287189.
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Nishiyama, Kenta. "Analysis of Soil-Tire Interaction Using a Two-Dimensional Finite Element-Discrete Element Method." Kyoto University, 2019. http://hdl.handle.net/2433/245298.
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Guzelbey, Ibrahim H. "Finite and boundary element analysis of elasto-plastic finite strain contact problems." Thesis, Cranfield University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335006.
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Aygunes, Haluk. "Finite element modeling of partially delaminated composite beams with contact-impact conditions." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA283726.
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Czekanski, Aleksander. "Novel nonlinear finite element analysis of dynamic contact problems using variational inequalities." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59014.pdf.
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Joshi, Prasad R. "An elastic contact theory for modeling vibration transmissibility through rolling element bearings." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1092882073.
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LI, JUNSHAN. "The Development of Semi-Analytical Solutions for 3-D Contact Problems." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1092069082.
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Uribe, Juan Camilo Mantilla. "Modelagem numérica e análise de modos de falha de conexões entre tubulares de revestimento de poços." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-07062017-103000/.
Повний текст джерелаАнотація:
Dependendo da magnitude, falhas na coluna de revestimento podem gerar grandes perdas econômicas e ambientais. Dada a complicada revisão e manutenção do revestimento durante a operação do poço, este deve ser projetado com robustez suficiente para suportar as solicitações em sua vida útil. As conexões de revestimento têm sido consideradas na literatura como os componentes mais propensos à falha. Testes são geralmente utilizados para qualificar a capacidade última das conexões no projeto de revestimento; porém, tendem a ser caros e demandam tempo considerável. Com o objetivo de diminuir os custos dos testes, modelos em elementos finitos são amplamente usados como alternativa e em complemento aos testes para avaliar o comportamento das conexões. Este trabalho apresenta um estudo de conexões de revestimento com base em modelos em elementos finitos, considerando a aplicação de torque de aperto, tração e pressão interna, tomando como caso de estudo uma conexão API 8 Round LTC 9 5/8 47 lb/ft L80. Na modelagem numérica adota-se axissimetría, a inclusão da elastoplasticidade com endurecimento isotrópico controlado pela superfície de falha de Von Mises, não linearidade geométrica e modelagem de contato para grandes deslizamentos com inclusão de fricção tangencial às superfícies de contato. Com uso de critérios mencionados na literatura e hipóteses de falha - principalmente dadas em função das pressões nos filetes, afastamento entre filetes e excessiva plasticidade - o modelo em elementos finitos desenvolvido foi utilizado para avaliar a capacidade da conexão ante os modos de falha por desacoplamento e vazamento. Os resultados da análise são satisfatórios quando comparados às resistências calculadas pela normativa API, e dados e observações experimentais presentes nas referências. Do estudo obtém-se um método para modelagem, que permite reproduzir os fenômenos observados em conexões de revestimento e estimar os modos de falha, podendo ser estendida a análise para conexões com diferentes geometrias. Este estudo é a base para pesquisas futuras sobre modelagem em elementos finitos de testes de conexões, definição de estados limites e de estudos de confiabilidade estrutural em conexões de revestimento de poço.Casing failures can potentially generate large economic losses and environmental damages, depending on their magnitude. Opportunities for casing evaluation and repair during operation are limited; hence, casing has to be designed with sufficient robustness to bear the loads applied during service life. Casing connections have been considered in the literature as the weak points of the casing column, following observed failures. Testing is generally used to qualify connections; however, they are expensive and demand a lot of time. Aiming to diminish the costs of testing, finite element models are widely used as an alternative and complement to tests to evaluate the behavior of casing connections. This work proposes to study casing connections using finite element models, considering the application of loads of make-up, traction, and internal pressure, taking for study case an API 8 Round LTC 9 5/8 casing connection. The finite element modeling assumed axisymmetry, elastoplastic material with isotropic hardening controlled by the Von Mises yielding surface, geometrical non linearity and inclusion of contact formulation for large slides and tangential frictional behavior between the casing connection mating surfaces. Using criteria mentioned in the literature - mainly in function of flank contact pressures, opening between flanks and effects of excessive plasticity - the developed finite element model was used to evaluate the capacity of the connection for jump-out and leakage failure modes. The results of the analyses were satisfactory when compared to the capacity calculated by the API standards, and experimental observations presented in the literature. From the study, a methodology is obtained for finite element modeling of casing connections, allowing study of the behavior and analysis of failure modes in casing connections, which can be extended for connections with different geometries. This study is the base for future investigations on finite element modeling of connection testing, on limit state definition for various failure modes, and for the study of structural reliability of casing connections.
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Krithivasan, Vijaykumar Jackson Robert Lloyd. "Finite element analysis of three-dimensional elasto-plastic sinusoidal contact and inclusion in a multi-scale rough surface contact model." Auburn, Ala., 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Mechanical_Engineering/Thesis/Krithivasan_Vijaykumar_55.pdf.
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