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Dissertations / Theses on the topic 'Materials Welded joints Finite element method'
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Grove, Alewyn Petrus. "Development of a finite element based nominal stress extraction procedure for fatigue analysis of welded structures." Diss., University of Pretoria, 2006. http://upetd.up.ac.za/thesis/available/etd-12182007-125836/.
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RABELLO, EMERSON G. "Uma nova proposta para inclusão dos efeitos da perda de restrição à plasticidade na caracterização do comportamento à fratura de aços ferríticos." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11266.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Doering, Kenneth Thomas Nathaniel. "Fatigue of friction stir welded lap joints with sealants." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Doering_09007dcc80627994.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 9, 2009) Includes bibliographical references (p. 118-127).
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Mahdavi, Shahri Meysam. "Fatigue Assessment of Friction Stir Welded Joints in Aluminium Profiles." Doctoral thesis, KTH, Materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92157.
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Friction stir welding (FSW) is a low heat input solid state welding technology. It is often used for fabrication of aluminium alloys in transportation applications including railway, shipbuilding, bridge structures and automotive components. In these applications the material is frequently subject to varying load conditions and fatigue failure is a critical issue. In most cases standard codes and fatigue guidelines for aluminium welded joints address only welded structures with conventional welding methods but not those with FSW procedure. In the scope of this thesis fatigue life assessment of friction stir welded components was performed using theoretical approaches along with finite element method (FEM). The further aim of this study was to generate a basis for standardization of fatigue assessment of friction stir welded joints. Friction stir welded hollow aluminium panels of alloy 6005A are investigated. The panels are used for train wall sides, train floors, deck and bridges. Each panel is made of several profiles that are joined with the friction stir welding method. Fatigue bending tests were performed for profiles in these panels. Fatigue cracks and failure appeared at notches in the profiles. With FEM simulations critical positions for crack initiation and failure were identified. The method of critical distance was used to analyse and estimate the fatigue life. It was shown that the failure location and fatigue limit could be predicted for both base metal and weld location. Choice of welding procedure (clamping condition) can significantly influence the fatigue life. It was shown that for some panels the critical distance method was not able to explain the failure in the weld. In this case fracture mechanics together with residual stress analysis were used successfully to predict the failure. Assuming homogeneous material properties throughout the weld and the base material, FEM analysis for T and overlap joints as well can provide a reasonable fatigue prediction. This suggests that the same assumption can be extended to complex components for failure analysis of the friction stir welded joints when using the critical distance method. Fatigue assessment of friction stir welded joints was also performed using standard codes Eurocode 9 and IIW. Fatigue curves of traditional fusion welded joints were used. The results are in reasonable agreement with experimental data and FEM predictions.QC 20120330
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Long, Xin. "Finite element analysis of residual stress generation during spot welding and its affect on fatigue behavior of spot welded joints." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4171.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 13, 2006) Vita. Includes bibliographical references.
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Romo, Arango Sebastian A. "Low-Cycle Fatigue of Low-Alloy Steel Welded Joints." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1573054310351145.
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Srinivasan, Shiva. "Characterization of stresses induced in doweled joints due to thermal and impact loads." Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2186.
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Thesis (M.S.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains x, 114 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 108-113).
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Nyström, Martin, and Tainan Pantano Tomaz. "Fatigue analysis of welded joints in a forestry machine : Utilizing the notch stress concept." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-45003.
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Welding is one of the most applied technics in the world for joining steel. Welds are liable to the phenomenon of fatigue, which is, primarily, the formation of a crack and consequently reduction of strength due to the action of time varying loads. Fatigue is one of the main causes of failure in steel structures. The aim of this thesis is to do static and dynamic analyses of a forestry crane with the purpose of using the analyses to determine the lifetime due to fatigue of welded components. Two methods for fatigue assessment are used in this work, the Hot-Spot Method and the Notch Stress Method. The first boom, which is a key component for the crane, is analyzed in a Finite Element Method (FEM) software. The found principal stress in accordance with the notch stress method in the first boom is ±165 MPa for the analyzed load case, rendering in a stress range of 330 MPa. The fatigue strength class FAT-225 (m=3), leads to an expected number of 633000 cycles, with a probability of survival of 97,7% for this case.Svetsning är en av de vanligaste teknikerna för sammanfogning av stål. Svetsar är känsliga för utmattning. Utmattningsfenomenet består primärt av en initial dislokation som genom tidsvarierande belastning formar en spricka som växer och därmed reducerar styrkan i konstruktionen. Utmattning är en av de vanligaste orsakerna till skador i stålkonstruktioner. Målet med detta arbete är att genomföra både statiska och dynamiska analyser av en skogsmaskins kran i avseende att bestämma utmattningslivslängden för dess svetsade konstruktioner. Två metoder för utvärdering används i detta arbete, hot-spot-metoden och notch-stress-metoden. Kranens första bom (lyftarmen) som är en huvudkomponent i kranen analyseras med hjälp av ett Finita Element program i enlighet med notch-metoden. Högsta funna spänningsvariationen i första huvudspänningsriktningen var ±165 MPa för ett av de analyserade lastfallen. Utmattningsklass FAT 225 (m=3) ger en uppskattning om utmattningslivslängd på 633000 cykler med en sannolikhet för överlevnad på 97.7% i detta fall.
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Roy, Samit. "A finite element analysis of adhesively bonded composite joints including geometric nonlinearity, nonlinear viscoelasticity, moisture diffusion and delayed failure." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/88624.
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A two-dimensional finite-element computational procedure is developed for the accurate analysis of the strains and stresses in adhesively bonded joints. The large displacements and rotations experienced by the adherends and the adhesive are taken into account by invoking the updated Lagrangian description of motion. The adhesive layer is modeled using Schapery's nonlinear single integral constitutive law for uniaxial and multiaxial states of stress. Effect of temperature and stress level on the viscoelastic response is taken into account by a nonlinear shift factor definition. Penetrant sorption is accounted for by a nonlinear Fickean diffusion model in which the diffusion coefficient is dependent on the penetrant concentration and the dilatational strain. A delayed failure criterion based on the Reiner-Weisenberg failure theory has also been implemented in the finite element code. The applicability of the proposed models is demonstrated by several numerical examples.Doctor of Philosophy
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Källgren, Therese. "Investigation and modelling of friction stir welded copper canisters." Doctoral thesis, KTH, Materialvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11999.
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This work has been focused on characterisation of FSW joints, and modelling of the process, both analytically and numerically. The Swedish model for final deposit of nuclear fuel waste is based on copper canisters as a corrosion barrier with an inner pressure holding insert of cast iron. Friction Stir Welding (FSW) is the method to seal the copper canister, a technique invented by The Welding Institute (TWI). The first simulations were based on Rosenthal’s analytical medium plate model. The model is simple to use, but has limitations. Finite element models (FEM) were developed, initially with a two-dimensional geometry. Due to the requirements of describing both the heat flow and the tool movement, three-dimensional models were developed. These models take into account heat transfer, material flow, and continuum mechanics. The geometries of the models are based on the simulation experiments carried out at TWI and at Swedish Nuclear Fuel Waste and Management Co (SKB). Temperature distribution, material flow and their effects on the thermal expansion were predicted for a full-scale canister and lid. The steady state solutions have been compared with temperature measurements, showing good agreement. In order to understand the material flow during welding a marker technique is used, which involves inserting dissimilar material into the weld zone before joining. Different materials are tested showing that brass rods are the most suitable material in these welds. After welding, the weld line is sliced, etched and examined by optical microscope. To understand the material flow further, and in the future predict the flow, a FEM is developed. This model and the etched samples are compared showing similar features. Furthermore, by using this model the area that is recrystallised can be predicted. The predicted area and the grain size and hardness profile agree well. Microstructure and hardness profiles have been investigated by optical microscopy, Scanning Electron Microscopy (SEM), Electron Back Scatter Diffraction (EBSD) and Rockwell hardness measurements. EBSD visualisation has been used to determine the grain size distribution and the appearance of twins and misorientation within grains. The orientation maps show a fine uniform equiaxed grain structure. The root of the weld exhibits the smallest grains and many annealing twins. The appearance of the nugget and the grain size depends on the position of the weld. A large difference can be seen both in hardness and grain size between the start of the weld and when the steady state is reached.QC20100719
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Vojtek, Jiří. "Statická analýza ocelových spojů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240122.
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Elaboration of design principles of steel joints. Creation of the finite element model in ANSYS program, the study of static behaviour near the bolt hole, deformation of the screw and the stress components of the welded joint. Comparison with the analytical formulas.
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Harman, Alex Bruce Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Optimisation and improvement of the design of scarf repairs to aircraft." Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2006. http://handle.unsw.edu.au/1959.4/26788.
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Flush repairs to military aircraft are expected to become more prevalent as more thick skin composites are used, particularly on the surface of the fuselage, wings and other external surfaces. The use of these repairs, whilst difficult to manufacture provide an aerodynamic, ???stealthy??? finish that is also more structurally efficient than overlap repairs. This research was undertaken to improve the design methodology of scarf repairs with reduced material removal and to investigate the damage tolerance of scarf repair to low velocity impact damage. Scarf repairs involve shallow bevel angles to ensure the shear stress in the adhesive does not exceed allowable strength. This is important when repairing structures that need to withstand hot and humid conditions, when the adhesive properties degrade. Therefore, considerable amounts of parent material must be machined away prior to repair. The tips of the repair patch and the parent laminate are very sharp, thus a scarf repair is susceptible to accidental damage. The original contributions include: ??? Developed analytic means of predicting the stresses within optimised scarf joints with dissimilar materials. New equations were developed and solved using numerical algorithms. ??? Verified using finite element modelling that a scarfed insert with dissimilar modulus subjected to uniaxial loading attracted the same amount of load as an insert without a scarf. As such, the simple analytic formula used to predict load attraction/diversion through a plate with an insert may be used to predict the load attraction/diversion into a scarf repair that contains a dissimilar adherend patch. ??? Developed a more efficient flush joint with a doubler insert placed near the mid line of the parent structure material. This joint configuration has a lower load eccentricity than external doubler joint. ??? Investigated the damage tolerance of scarf joints, with and without the external doubler. The results showed that scarf joints without external doublers exhibited a considerable strength reduction following low velocity impact. Based on the observations, the major damage mechanics in the scarf joint region following impact have been identified. These results demonstrated that it is important to incorporate damage tolerance in the design of scarf repairs.
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Vautier, Isabelle. "Influence du contact unilatéral sur le comportement vibratoire de coques soudées par points." Châtenay-Malabry, Ecole centrale de Paris, 1994. http://www.theses.fr/1994ECAP0363.
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Nous présentons dans cette thèse une modélisation du contact unilatéral entre coques soudées en dynamique et donnons des informations qualitatives sur l'influence de ces phénomènes sur la réponse en fréquence des structures. Notre objectif est une meilleure compréhension des mécanismes de transmission des vibrations et des bruits dans les voitures. Le modèle de coques minces utilise est celui de Koiter, traité par une formulation mixte proposée par Ph. Destuynder et M. Salaun. Les soudures sont représentées comme des corps rigides. Le contact unilatéral, suppose sans frottement, est pris en compte par une méthode de dualité permettant d'éviter l'interpénétration des sous-structures nœud à nœud, le multiplicateur de Lagrange représentant l'effort de contact normal. Comme le phénomène est non linéaire, nous effectuons une résolution des équations dans le domaine temporel, suivie d'une analyse de Fourier. Les équations du contact sont résolues par un algorithme de points intérieurs très efficace du AJ. Herskovits, dans le cadre d'une intégration en temps par la méthode de Neuwmark. On présente également différentes formes d'excitations large bande permettant d'obtenir la réponse de la structure dans une gamme de fréquences donnée, et en particulier la technique du MLS. Divers outils de traitement du signal sont également adaptés ou construits en vue de l'interprétation quantitative des résultats ; un panorama rapide de quelques éléments de psycho-acoustique permet, quant à lui, d'obtenir des conclusions qualitatives en termes de gène auditive. L'implémentation des modèles est faite dans le code éléments finis Héraclès, qui est valide en statique et en dynamique sur des cas simples et sur des pièces industrielles. Nous observons alors que le contact unilatéral modifie de façon importante le spectre de réponse: renforcement de certaines composantes fréquentielles, création de nouvelles fréquences, apparition de bruit large bande, et modulations d'amplitudes de certaines fréquences, ce qui est gênant pour l'oreille
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Štěrba, Martin. "Analýza svarů s využitím metody konečných prvků." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372183.
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This diploma thesis is concerned with the numerical analysis of welded aluminim structures. In these structures, there are significant decreases in the mechanical properties at the area of the weld and in the heat affected zone as a result of welding. Within this thesis, simulations of quasi-statically loaded welded joints made from EN AW-6082 T6 alloy were performed to investigate the load capacity and ductility of these joints. Computations were performed using a programme system based on an explicit finite element method. To describe material anisotrophy, a nonlinear material model called the Weak texture model was chosen. Material properties of the weld and the heat affected zone were considered to be different from base material. The required material parameters were adopted from available literature, however, material tests and indetification procedure of these parameters were described. In comparison with the experimental data, the results of the numerical simulations showed a relatively good ability of models to capture load capacity of studied welded joints. Nevertheless, due to mesh sensitivity of models caused by localization of deformation, it was not possible to determine ductility of these joints.
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Alam, Md Rabiul. "Crack identification in an offshore structural frame through static substructuring and finite element method /." 2001.
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