Finite Element Methods

En el presente trabajo se estudia el proceso de friction stir spot welding de planchuelas de aleación de aluminio AA6082 utilizando dos métodos de cálculo sucesivos. En una primera etapa se modela la inserción del perno en el material a soldar como un problema unidimensional axisimétrico no estacionario.De este caso se extrae el campo de temperaturas que es utilizado como campo de condiciones térmicas iniciales al momento de modelar el proceso de permanencia en el paso siguiente. Esta segunda etapa del proceso se realiza mediante un modelo bidimensional axisimétrico considerando al material constitutivamenteviscoplástico y, consecuentemente, resolviendo un problema de flujo de Stokes con viscosidades no lineales. Como resultados de este caso se obtienen los campos de velocidades, temperaturas y tensiones para todo el continuo. Las estimaciones realizadas se comparan con resultados experimentales de soldaduras de punto por fricción agitación.In this work, the friction stir spot weldi...

La soldadura de punto por friccion agitacion o FSSW, es un metodo de union del tipo traslape (lap joint) de materiales, cada vez mas utilizado en la industria naval. Se utiliza para unir principalmente aleaciones de aluminio y aceros. Presenta ventajas frente a la soldadura de arco ya que permite soldar materiales disimiles, requiere menor energia y no produce radiacion ni gases toxicos. Actualmente, se encuentra insatisfecha para la industria la necesidad de soldar espesores de aleaciones de aluminio mayores a 3mm. En la literatura sobre el tema se hallo una variedad de tecnicas y de modelos constitutivos para representar el comportamiento de los materiales, asi como tambien para el modelado de las condiciones de friccion, sin encontrarse aun lo mas adecuado para su estudio. Se determinaron como las dos variables mas importantes a la relacion diametro del hombro de la herramienta y las condiciones de contacto entre herramienta y material. En esta direccion, y buscando determinar la...

El proceso de soldadura de punto por friccion consiste en una herramienta giratoria que, a traves de la presion y el calor generado por el trabajado mecanico, logra la union de las piezas. En este trabajo se modelo dicho proceso utilizando la tecnica de elementos finitos. Se implemento un modelo termomecanico axisimetrico de elementos finitos con el fin de reducir el costo computacional. Se implemento una malla adaptativa para poder simular el proceso de insercion de la herramienta en el material. Los resultados de simulaciones con distintos parametros de proceso nos permitieron reconocer los efectos sobre la zona termomecanicamente afectada, la cual esta relacionada con la resistencia de la soldadura.

In this work, the friction stir spot welding process of AA6082 aluminium allow slabs is studied by means of two different methods of calculation. Firstly, the pin insertion is modelled as an axisymmetric one dimensional non stationary problem. The resulting temperatures field is used in the second phase of calculus as initial thermal conditions at the moment of modelling the following tool dwelling process. This second phase the welding process is modelled using an axysimmetric continuum, assuming a viscoplastic material, therefore solving a Stokes’ flow problem with non linear viscosity. The velocity, temperatures and stress fields are obtained for the whole domain. The obtained results are compared to experimental results in friction stir spot weldments. Mecánica Computacional Vol XXXVI, págs. 511-520 (artículo completo) José G. Etse, Bibiana M. Luccioni, Martín A. Pucheta, Mario A. Storti (Eds.) San Miguel de Tucumán, 6-9 Noviembre 2018 Copyright © 2018 Asociación Argentina de Me...

The paper presents an application of the Galerkin triangular mesh finite element method using linear approximation, in axisymmetrical and plane geometry, to the design of liquid metal annular induction pumps. a casing around the stator chanelling the ventilation air flow.

Corrosion in concrete prevents in-situ observation, necessitating models to provide insight into the local reaction currents. We present a computational method for predicting corrosion rates of reinforcements within concrete under natural conditions, i.e. requiring the corrosion current to be supported by equal cathodic currents. In contrast to typical corrosion models, where these two counteracting currents are required to be co-located, we allow these currents to be separated such that pitting corrosion can be supported by cathodic reactions over a much larger area. Pitting corrosion is investigated, elucidating the effects of the concrete porosity and water saturation, the presence of dissolved oxygen, and chlorine concentration within the pore solution. The presented model is capable of capturing the dynamic growth of acidic regions around corrosion pits, showing the limited region over which the hydrogen evolution reaction occurs and how this region evolves over time. The ability of oxygen to diffuse towards the metal surface due to increased porosity is seen to have a major effect on the corrosion rate, whereas changes in the chlorine concentration (and thus changes in the conductivity of the pore solution) play a secondary role. Furthermore, external oxygen is seen to enhance corrosion but is not required to initialise and sustain acidic corrosion pits.

The joining techniques of lightweight and strong materials in the transport industry (e.g. automotive, aerospace, shipbuilding industries) are very important for the safety of the entire structure. In these industries, when compared with other joining methods, the use of adhesively bonded joints presents unique properties such as greater strength, design flexibility, and reduction in fuel consumption, all thanks to low weight. The aim of this study was the analysis of the tensile fatigue behavior of adhesively bonded glass fiber/epoxy laminated composite single-lap joints with three different specimen types including 30, 40 and 50 mm overlap lengths. In this study, composite adherents were manufactured via vacuum-assisted resin transfer molding and were bonded using Loctite 9461 A&B toughened epoxy adhesive. The effect of a surface treatment method on the bonding strength was considered and it led to an increment of about 40%. A numerical analysis based on a finite element model was...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

For many reasons Finite Element Method is very useful especially in biomechanical researches .One of them is difficulty of gaining real specimens for in vitro tests. The second one is that FEM provides relatively easy way to check how changing some parameters of spine geometry or materials, influences on spine segment behavior. Consider it, many research centers in whole world in last years started to prepare FEM models of spine. Some of them are quite simple, some are very advanced. This paper is a review of three chosen FEM lumbar spine models, made in different scientific centers in last years. Authors present their opinions about possibilities of using material coefficients of particular structures of spine in own model. It could be useful for anybody who wants to build proprietary spine model. Authors met many problems trying to obtain material coefficients from literature which may be adopted to own spine model. Models reviewed in this paper could be important assistance for creating own spine models.

Implementation of new spine stabilisation systems should be preceded by the analysis of the behaviour of healthy and damaged spine under laboratory conditions. Research was performed on two-part and three-part segments without damage and with disc damage in the two-part segment, and with a wedge cut in the vertebra in the three-part segment. In the two-part segment, a relative power necessary for inducing extension-compression in the damaged segment is twice as high as in the damaged three-part segment. In the damaged two-part segment, the motion in the sagittal plane needs a relative power being more than twice as high as in the damaged three-part segment. Yet absolute average values of powers examined in the two-part and three-part segment systems in the undamaged spine for all types of motion were similar, with slight advantage of the two-part segment system. Basic two-part segment of the spine motion system is its most stable functional part.

A series of tests and also numerical analyses were conducted to explore the mechanical behaviour of a mixture of coarse gravel-size particles floating in a matrix of clay. The research is a step forward in an on-going investigation on behaviour of composite clay, which is used as the core material of some large embankment dams all over the world. This paper focuses on a predominant feature of the composite soil behaviour: increase of non-deformable solid inclusions in a mixture leads to formation of heterogeneity of stress field, excess pore water pressure and strain distribution along the specimens. By the aid of numerical analyses, it is clarified through the paper that in addition to loading details, position of inclusions relative to loading direction also affects heterogeneity of stress/strain and excess pore water pressure distribution through the mixture. Despite the former, the latter redistributes with a rate proportional to material hydraulic conductivity, based on the analyses results described in the paper.

As a step forward in an ongoing investigation on behaviour of composite clay, which is used as the core material of some large embankment dams all over the world, a series of experiments were conducted to explore the distribution of excess pore water pressure along saturated triaxial clay specimens during cyclic loading. As the predominant feature of the composite clay behaviour is increase of excess pore water pressure in both monotonic and cyclic loadings as a consequence of increase of inclusion content, this paper focuses on formation of such pressure distribution inside the specimen by utilizing a miniature inner pressure transducer inside triaxial specimens. Specimens of pure clay, mixed material containing 40% (volumetric) ceramic beads and 60% clay, and pure clay with the inner transducer surrounded by inclusions were tested. Under cycles of 1.5% strain amplitude the expected increase of excess pore water pressure was captured at both ends and also inside the mixed specimen, and also by the transducer surrounded by inclusions, compared with pure specimens, which is in agreement with previous findings in this regard. Comme un pas en avant dans une enquête en cours sur le comportement de l'argile composite, qui est utilisé comme matériau de base de certains grands barrages en remblai dans le monde entier, une série d'expériences ont été réalisées pour étudier la distribution de la pression interstitielle le long de l'excès d'eau saturée en argile triaxial échantillons durant le chargement cyclique. Comme la caractéristique prédominante du comportement d'argile composite est l'augmentation de la pression interstitielle de l'eau en excès dans les deux chargements monotones et cycliques comme une conséquence de l'augmentation de la teneur en inclusion, ce document met l'accent sur la formation de la distribution de telles pressions à l'intérieur de l'échantillon en utilisant un capteur de pression miniature intérieure l'intérieur des échantillons triaxiaux. Les échantillons d'argile pure, matériau mixte contenant 40% (volumétrique) billes de céramique et 60% d'argile et d'argile pure avec le transducteur intérieure entourée par des inclusions ont été testés. En vertu de cycles de 1.5% amplitude de la déformation l'augmentation prévue de la pression interstitielle excès d'eau a été capturé aux deux extrémités et aussi à l'intérieur du spécimen mixtes, et aussi par le transducteur entourée par des inclusions, par rapport aux échantillons pure, qui est en accord avec les conclusions antérieures dans ce égard.

We present new serial and parallel algorithms for multilevel graph partitioning. Our algorithm has coarsening, partitioning and uncoarsening phases like other multilevel partitioning methods. However, we choose fixed nodes which are at least a specified distance away from each other and coarsen them with their neighbor nodes in the coarsening phase using various heuristics. Using this algorithm, it is possible to obtain theoretically and experimentally much more balanced partitions with substantially decreased total edge costs between the partitions than other algorithms. We also developed a parallel method for the fixed centered partitioning algorithm. It is shown that parallel fixed centered partitioning obtains significant speedups compared to the serial case. …

Realistic virtual models of leaf surfaces are important for several applications in the plant sciences, such as modelling agrichemical spray droplet movement and spreading on the surface. In this context, the virtual surfaces are required to be smooth enough to facilitate the use of the mathematical equations that govern the motion of the droplet. Although an effective approach is to apply discrete smoothing D2-spline algorithms to reconstruct the leaf surfaces from three-dimensional scanned data, difficulties arise when dealing with wheat (Triticum aestivum L.) leaves, which tend to twist and bend. To overcome this topological difficulty, we develop a parameterisation technique that rotates and translates the original data, allowing the surface to be fitted using the discrete smoothing D2-spline methods in the new parameter space. Our algorithm uses finite element methods to represent the surface as a linear combination of compactly supported shape functions. Numerical results conf...

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

CONTENT – General description of the course The course familiarizes the participant with: (a) Basic features of problem-driven and systematic (deductive) theory construction, model building, and explanation in social science, including macroand micro-features of explanatory models as well as macro-micro-macro transitions. This short first part of the course provides an introduction to the general approach to social science theory formation and research that underlies the topics discussed in the subsequent parts. (b) Social embeddedness and trust. The first application in which part (a) is brought into action focuses on network explanation for social dilemma problems such as cooperation problems and trust problems. Theoretical models as well as empirical tests of these models will be discussed. (c) Social capital. The second application in which part (a) is brought into action focuses on social capital. Again first some theoretical principles will be introduced. Thereafter different ...

Single point incremental forming (SPIF) is an emerging application in sheet metal prototyping and small batch production, which enables dieless production of sheet metal parts. This research area has grown in the last years, both experimentally and numerically. However, numerical investigations into SPIF process need further improvement to predict the formed shape correctly and faster than current approaches. The current work aims the use of an adaptive remeshing technique, originally developed for shell and later extended to 3D "brick" elements, leading to a Reduced Enhanced Solid-Shell formulation. The CPU time reduction is a demanded request to perform the numerical simulations. A two-slope pyramid shape is used to carry out the numerical simulation and modelling. Its geometric difficulty on the numerical shape prediction and the through thickness stress behaviour are the main analysis targets in the present work. This work confirmed a significant CPU time reduction and an acceptable shape prediction accuracy using an adaptive remeshing method combined with the selected solid-shell element. The stress distribution in thickness direction revealed the occurrence of bending/unbending plus stretching and plastic deformation in regions far from the local deformation in the tool vicinity.

The laser hot-wire (LHW) process has the potential to deposit material at high rates using low laser power. An LHW experiment was designed to be able to deposit material at the rate of 3.46 kg per hour with less than 10 kW of laser power. Four thermocouples were built into the substrate to record the temperature variation during the deposition. The results show that temperature fluctuates in a periodic manner with the deposition layer by layer. Simultaneously, the distortion of the substrate was measured. The substrate is distorted, and the maximum distortion increases gradually during deposition. The equivalent heat conduction coefficient for heat convection in the molten pool is discussed. It becomes apparent that the heat convection of flowing molten metal is 3-5 times that of molten metal at rest. The absorptivity of laser power was determined by comparison between the simulation and a one-pass cladding experiment. The absorptivity of laser power is approximately 15% in this experiment. Numerical simulation of LHW additive manufacturing was conducted to obtain the temperature, stress and strain fields, and the distortion. The outstanding features for numerical simulation are additive geometry and numerous analysis steps. The INP files of ABAQUS are compiled in a Matlab program because of the considerable number of steps and element definitions. Temperature variation and substrate distortion are both measured to validate the FEA model. The verification result indicates that the LHW model is feasible and accurate. The maximum residual stress is located in the junction between the deposit and substrate when the deposition is finished. This junction area becomes the most likely crack position. Deposited material undergoes complicated thermal cycles during the LHW process. Temperature variation determines the phase transformation. The microstructure change of the heat affected zone was analyzed on the basis of computational temperature variation. Such interpretation can effectively explain softened area in the heat affected zone of the substrate. A numerical computation method is used to map the processing window of stable hot-wire deposition. It is shown that the stable deposition has top and bottom limitations under a certain current intensity and wire feed speed.

This report presents the development, characterization, and arc-jet testing of Phenolic Impregnated Carbon Ablators (PICA), a member of the Lightweight Ceramic Ablators (LCA) family developed at Ames Research Center. LCAs consist of a low density fibrous substrate impregnated with an organic resin. PICA uses a preformed fibrous carbon tile manufactured by Fiber Materials, Inc. as the substrate, and phenolic as the organic infiltrant. Innovative infiltration techniques were developed to produce PICA with densities ranging from 14 to 65 lbm/ft3; however, only the low density PICA samples were used to evaluate the material's thermal performance. Arc-jet testing of low density PICA showed that these materials can withstand very high heating rates and surface pressures and are more mass efficient than most traditional ablative materials (ref. 1). The manufacturing process of PICA has since been refined to give repeatable performance among batches, and its thermal performance is being further evaluated. Surface densification was also recently developed to improve the ablation characteristics in high heating and surface pressure environments. The thermal performance and ablation characteristics of PICA were evaluated in an oxidizing environment in the Ames Research Center 60 megawatt (MW) Interaction Heating Facility (IHF). Samples of PICA with and without surface densification, the carbon preform, and Avcoat-5026 (the Apollo heat shield), were tested at cold wall heat fluxes of 375 to 2960 Btu/ft2-s and surface pressures from 0.1 to 0.43 atm. Resulting heat loads during these tests ranged from 5500 to 29,600 Btu/ft 2. Surface and in-depth temperatures were measured using optical pyrometers and thermocouples, respectively. Mass loss was measured for each sample and surface recession was measured using a height gage. Various material characterization tests were also performed on virgin (pre-test) and charred (post-test) PICA samples.

Linear induction motor modeling and the equivalence with the asymmetrical rotary induction motor. ... Euler Bueno dos Santos, MSc Luciano Martins Neto, Dr José Roberto Camacho, PhD ... Universidade Federal de Goiás Universidade Federal de Uberlândia, School of ...

In the present work three-dimensional Finite Element (FE) transient thermal analysis of friction stir welding have been presented. It was observed that most of the research on thermal history analysis of Friction Stir Welding (FSW) considered only frictional heat generation. In this present work the source of heat generation have been assumed to be both friction between the tool and work piece interface and shear deformation of material. A comparative study has been done between thermal history prediction by heat generation due to friction and heat generation due to both friction and shear deformation of material. The numerically predicted thermal profiles compared well with those of the experimental results with less error thus validating the various assumptions made in the work.

Temperatura crítica, Resistência ao fogo, Elementos mistos aço betão Resumo. Neste trabalho são apresentados resultados de ensaios realizados sob acção do fogo em elementos mistos de aço e betão, constituídos por perfis laminados, parcialmente revestidos com betão armado. Os ensaios foram realizados de acordo com a norma europeia de ensaios de resistência ao fogo EN1363 parte 1. Os elementos foram ensaiados à flexão sob acção da curva de incêndio padrão ISO834. A temperatura crítica e a resistência ao fogo foram determinadas para o estado limite último de doze elementos, para três graus de utilização (40, 60 e 80%) e para diferentes configurações dos estribos (soldados e não soldados). Foi utilizado um modelo de elementos finitos para validar a temperatura medida nos diferentes materiais (aço do perfil, betão e reforço) e o deslocamento sofrido pelo elemento. O modelo termo-mecânico foi comparado com os ensaios realizados, utilizando elementos tridimensionais e elementos de interface para simular a transferência de calor e a adesão entre os blocos de betão armado e o perfil metálico. Os resultados numéricos confirmam as medições experimentais em todas as vertentes, quando comparados deslocamentos e temperaturas.

O aço inoxidável tem reconhecidamente uma resistência ao fogo superior ao aço carbono pelo que é de prever uma crescente utilização deste tipo de aço para fins estruturais. De facto, embora mais caro que o aço carbono, o aço inoxidável pode conduzir a estruturas competitivas em virtude de necessitarem de uma menor quantidade de material de protecção térmica ou mesmo, em alguns casos, não ser necessária protecção contra incêndio, como sucede na estrutura apresentada neste artigo. Com o objectivo de modelar pelo Método dos Elementos Finitos o comportamento de uma estrutura porticada de um edifício em aço inoxidável em situação de incêndio, introduziu-se a sua lei constitutiva no programa SAFIR, um programa de elementos finitos para análise não-linear geométrica e material, especialmente desenvolvido na Universidade de Liège para estudo de estruturas sujeitas à acção do fogo. Neste programa as propriedades térmicas e mecânicas do aço são função da temperatura, de acordo com o Eurocódigo 3. Compara-se o comportamento da estrutura em aço inoxidável 1.4301 (também conhecido como 304) com o comportamento que teria se a estrutura fosse em aço carbono S235 e realçam-se os benefícios da utilização do aço inoxidável resultantes da sua maior resistência ao fogo. A utilização do aço inoxidável para fins estruturais tem estado reservada a projectos de elevado valor arquitectónico em que o carácter inovador das soluções adoptadas constitui

Foi utilizado um forno de resistência ao fogo, com a prescrição da curva ISO834. Neste trabalho são apresentados os resultados da evolução da temperatura nos painéis perfurados, nas vigas, conetores, superfície não exposta e apresentados resultados da taxa de carbonização de cada célula.

As lajes em madeira são estruturas leves, de fácil montagem, com excelentes características arquitetónicas, térmicas e acústicas. No entanto, a sua elevada vulnerabilidade ao fogo, obriga a que se determine e avalie o seu comportamento com rigor. Com base em ensaios experimentais, realizados para a determinação da resistência ao fogo, será possível validar um modelo de laje numérico desenvolvido com a utilização de um programa de elementos finitos, ANSYS. O modelo numérico é transiente térmico, não linear e utiliza elementos hexaédricos. Considerou-se a não linearidade das propriedades a temperaturas elevadas. As condições de fronteira, admitidas no problema, são de convecção e radiação, sendo consideradas curvas típicas para a evolução da temperatura. Estas curvas foram registadas durante os ensaios experimentais e permitiram simular o efeito da ação do fogo na superfície exposta, interior das cavidades celulares e nas aberturas ou perfurações da laje. O comportamento físico da laje é também condicionado pela formação da carbonização, sendo este fenómeno considerado no modelo numérico.

This paper presents a three-dimensional computational model for nonlinear microwave heating problems. In order to reduce the computational costs, a new finite element method adaptive time-stepping scheme is proposed. Numerical results are compared with experimental measurements on a problem of dielectric heating of water.

Transformer saturation is an area of major concern as the transformers are designed to run near peak magnetizing flux value and if voltage/frequency (V/f) ratio increases, it may cause the transformer to reach into saturation, which can affect normal operation of the transformer and even cause mal-operation of the protective equipments. This paper explains different techniques of transformer saturation detection and current waveform improvement.

Structural health monitoring (SHM) is crucial for monitoring structures performance, detecting the initiation of flaws and damages, and predicting structural life span. The dissertation emphasizes on developing analytical and numerical models for ultrasonics transduction between piezoelectric wafer active sensors (PWAS), and metallic and composite structures. The first objective of this research is studying the power and energy transduction between PWAS and structure for the aim of optimizing guided waves mode tuning and PWAS electromechanical (E/M) impedance for power-efficient SHM systems. Analytical models for power and energy were developed based on exact Lamb wave solution with application on multimodal Lamb wave situations that exist at high excitation frequencies and/or relatively thick structures. Experimental validation was conducted using Scanning Laser Doppler Vibrometer. The second objective of this work focuses on shear horizontal (SH) PWAS which are poled in the thickness-shear direction (d 35 mode). Analytical and finite element predictive models of the E/M impedance of the free and bonded SH-PWAS were developed. Next, the wave propagation method has been considered for isotropic materials. Finally, the power and energy of SH waves were analytically modeled and a MATLAB graphical user interface (GUI) was developed for determining the phase and group velocities, modeshapes, and the energy of SH waves. vi The third objective focuses on guided wave propagation in composites. The transfer matrix method (TMM) has been used to calculate dispersion curves of guided waves in composites. TMM suffers numerical instability at high frequency-thickness values, especially in multilayered composites. A method of using stiffness matrix method was investigated to overcome instability. A procedure of using combined stiffness transfer matrix method (STMM) was presented and coded in MATLAB. This was followed by a comparative study between commonly used methods for the calculation of ultrasonic guided waves in composites, e.g. global matrix method (GMM), semianalytical finite element (SAFE).

In the construction of Roller compacted Concrete Dams (RCD), two types of internal and external concrete are used; thermal cracks are occurred due to hydration of various cements in this type of dams. Ignorance of this issue can lead to crack formation in the susceptible points of the dams. In this research, the behavior of the thermal cracks existed in the RCD body, is investigated through translational and rotational components of the earthquake. Three-dimensional Finite Element (FE) model of the concrete dam is built in Abacus software, and the model was subjected to 7 earthquake records. After validation of the model, the propagation of the crack existed in the dam body is evaluated using fracture mechanics criterion. The results of the FE analysis show that the existence of the cracks in the susceptible points of the dam, leads to propagation of these cracks during an earthquake. Especially, with considering the rotational component of the earthquake which has the significant contribution in the obtained values of the crack propagation criterion; this contribution is related to the frequency content of the earthquake, which can lead to an increase of the crack propagation energy up to 50 percent in some earthquake records.

Reinforced concrete (RC) columns of skewed and curved bridges and bridges with unequal spans and column heights can be subjected to combined loadings including axial, flexure, shear and torsion during an earthquake. Multi-directional earthquake motions with significant ...

SUMMARY The aiin of this paper is the solution of the shape optimization problem for simply and multiply-connected orthotropic sections under Saint-Venant torsion by using the Boundary Element Method. The objective function is the area of the section, while the only constraint corresponds to a given torsional stiffness. The nonlinear optimization algorithm is also discussed, so they are the different

The soil is a heterogeneous and anisotropic medium. Hydraulic conductivity, an intrinsic property of natural alluvial deposits varies both deterministically and randomly in space and has different values in various directions. In the present study, the permeability of natural deposits and its influence on the seepage flow through a natural alluvial deposit is studied. The 2D Finite Difference code, FLAC 5.0, is used for modeling permeability as a random variable with lognormal distribution and correlated structure. Effect of spatially varying permeability on the seepage flow through deposit is investigated for both isotropic and anisotropic conditions. Results show that in isotropic condition, the mean discharge flow rate calculated from stochastic analyses is less than the equivalent deterministic value and this reduction depends on the coefficient of variation, COV of permeability and the correlation length. The directionality of permeability introduced as mechanical anisotropy was also studied along with the heterogeneity. It was found that increasing the anisotropy ratio of permeability leads to the formation of horizontal flow canals and increasing the seepage flow consequently at a constant vertical permeability. Variation of permeability coefficient was found to have almost no impact on mean discharge flow rate for anisotropic fields in comparison to the isotropic condition.

Hole-flanging is a crucial operation in sheet metal forming technology, where the material around a prefabricated hole is deformed by a spherical, conical, or cylindrical punch to create a flanged hole wall. This study aims to determine the limiting hole-flanging coefficient of AA1050-O aluminum alloy sheet using the Cockroft-Latham ductile fracture criterion. Numerical simulations of the hole-flanging process using the Cockroft-Latham ductile fracture criterion were conducted to identify the limiting hole-flanging coefficient of AA1050-O aluminum alloy sheet. The limiting hole-flanging coefficient of the material was found to be 0.61 and was further verified through experiments. Additionally, the effects of the hole-flanging coefficient on the Cockroft-Latham damage value, minimum thickness, and height of the flanged hole wall were evaluated within the formability region of the material when the coefficient exceeded the limiting value. The findings from this study provide valuable insights for designing hole-flanging operations for AA1050-O aluminum alloy sheet.

Les choix technologiques sont naturellement orientés vers l'utilisation des pièces légères dont au moins une des dimensions est beaucoup plus petite que les autres, tels que des profils ou des plaques, mais le comportement des pièces souples présente des défis particuliers pour les ingénieurs lors de la spécification géométrique, la raison est que les pièces souples peuvent prendre à l'état libre une forme substantiellement différente de leur géométrie nominale. Avec le développement de la conception des systèmes mécaniques, les méthodes traditionnelles d'analyse des tolérances, tels que la méthode pire des cas et la simulation de Monte Carlo, ne sont pas applicables à des assemblages flexibles en raison de la déformation possible de la pièce pendant le processus d'assemblage. Cette communication porte sur la présentation du tolérancement des mécanismes déformables à travers l'illustration de la problématique générale afin d'aborder dans un deuxième temps une étude des mécanismes déformables (flexibles) en utilisant la méthode des coefficients d'influence et enfin la modélisation d'un mécanisme de ce type à travers un exemple en vue d'une analyse des tolérances dimensionnelles et géométriques. Mots clefs -tolérancement, analyse des tolérances; mécanismes déformables ; méthode de Monte Carlo ; méthode des coefficients d'influence.

A numerical investigation has been adopted to study chemical reaction effect on free convective flow past an accelerated moving vertical plate with ramped temperature. The governing equations of flow, heat and mass transfer are solved by employing finite element method. Numerical results for the velocity, temperature and concentration distributions for various parametric values are reported graphically and discussed. The influence of various important parameters on primary skin-friction coefficient, secondary skin-friction coefficient and the Nusselt number are shown in a tabular form. The accuracy of the numerical method is validated by a direct comparison with previously published work and found that there is an excellent agreement between the results exists.

I detta examensarbete har en studie genomförts av hur väl 3D-skrivning kan tillämpas i Volvo Cars i Skövdes produktion. En litteraturstudie har genomförts för att åskådliggöra de olika 3Dskrivningsteknikerna och deras användningsområde. För att på ett överskådligt sätt jämföra de olika teknikernas duglighet har en bedömningsskala utvecklad av Nasa använts. Denna skala benämns som Technology Readiness Level (TRL). Den teknik som bedöms som mest lämplig med avseende på fullskalig produktion samt prototyptillverkning är Selective laser melting (SLM). För att åskådliggöra fördelar med 3D-skrivare har en förenklad 3D-modell av Volvos cylinderblock I5D modellerats. Denna förenklade modell har sedan modifierats för att åstadkomma en temperatursänkning som kan möjliggöra ett högre effektuttag. Två varianter av topologiska modifieringar presenteras. För dessa modifieringar har sedan värmelaster och kylning applicerats för att analysera värmespridningen i cylinderblocket. Jämförande mellan originaldesignen och de topologiska modifieringarna har sedan utförts. Målet med detta var att sänka den kritiska temperaturen i cylinderväggarna med åtminstone 35°C. Beräkningar har utförts med PTC/Creo. Med hjälp av TRL-skalan bedöms Selective laser melting vara den teknik som är mest lämplig för Volvo Cars i Skövde att tillämpa med avseende på prototyptillverkning. Med avseende på fullskalig produktion anses ingen av de teknikern som benämns i arbetet vara lämpliga. Resultatet visar att genom topologiska modifieringar kan temperaturen i det kritiska området sänkas med upp till 51 °C. En enkel kostnadsberäkning har utförts för att uppskatta hur mycket ett cylinderblock skulle kosta om den traditionella tillverkningen ersattes med 3D-skrivare. Detta visar att ett cylinderblock av typen I5D skulle kosta cirka 10 853 kr att tillverka med 3D-skrivaren X line 1000 R. I det priset är inte inköp av 3D-skrivaren inräknat. Rapporten diskuteras också följderna av resultatet. Vilka de potentiella felkällorna kan vara och vad som kan ha gjorts annorlunda. Det diskuteras också hur framtiden ser ut för 3D-skrivning och vad som skulle kunna göras som en naturlig fortsättning på detta examensarbete.

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