A technology for optimization of potential parameters from condensed phase simulations (POP) is discussed and illustrated. It is based on direct calculations of the derivatives of macroscopic observables with respect to the potential parameters. The derivatives are used in a local minimization scheme, comparing simulated and experimental data. In particular, we show that the Newton Trust-Region protocol allows for accurate and robust optimization. POP is illustrated for a toy problem of alanine dipeptide and is applied to folding of the peptide WAAAH. The helix fraction is highly sensitive to the potential parameters while the slope of the melting curve is not. The sensitivity variations make it difficult to satisfy both observations simultaneously. We conjecture that there is no set of parameters that reproduces experimental melting curves of short peptides that are modeled with the usual functional form of a force field. We then apply the newly developed technology to study the liquid mixture of tert-butanol and water. We are able to obtain, after 4 iterations, the correct phase behavior and accurately predict the value of the Kirkwood Buff (KB) integrals. We further illustrate that a potential that is determined solely by KB information, or the pair correlation function, is not necessarily unique. / text

Deformation and partial melting have long been recognized to occur together, but differentiating which actually occurred first has remained enigmatic. Prevailing theories suggest that partial melting typically occurs first, and deformation is localized into melt-rich areas because they are rheologically weak. However, evidence from three different areas, suggests the role of strain has been underestimated in localizing partial melting. The Wet Mountains of central Colorado provide evidence for synchronous partial melting and deformation, with each process enhancing the other. Throughout the Wet Mountains, deformation is concentrated in areas where melt producing reactions occurred, and melt appears to be localized along deformation-related features. Melt microstructures present within the Wet Mountains correlate well with crustal-scale plutons and magmatic bodies and provide a proxy for crustal-scale melt flow. Granitic gneisses from the Llano Uplift, central Texas, provide evidence for partial melting occurring within small-scale shear zones and surrounding country rocks, synchronously. In the field, shear zones appear to contain former melt, whereas the country rock does not provide macroscopic evidence for partial melting. However, detailed microstructural investigation of shear zones and country rocks indicates the same density of melt microstructures, in both rock types. Melt microstructures are important for understanding the full melting history of a rock and without detailed structural and petrographic analysis, erroneous conclusions may be reached. Granulite-facies migmatites of the Albany-Fraser Orogen, southwestern Australia, have undergone partial melting, synchronous with three phases of bidirectional extension. Four major groups of leucosomes, including: foliation-parallel, cross-cutting, boudin neck and jumbled channelway leucosomes and late pegmatites were analyzed via whole-rock geochemistry, and there is evidence for fluid-saturated and -undersaturated biotite- and amphibole-dehydration melting. Migmatites from these three locations contain pseudomorphs of melt along subgrain and grain boundaries, areas of high dislocation density, in quartz and plagioclase. For these rocks that involve multicomponent systems, the primary cause for preferential melting in high strain locations is enhanced diffusion rates along the subgrain boundary because of pipe diffusion or water associated with dislocations. / text

Composition and texture of the Middle and Late Eocene volcanic, volcaniclastic, and volcanic-sedimentary rocks in the Bijgerd-Kuh e Kharchin area, in the Uromieh-Dokhtar zone northwest of Saveh, Iran, suggest the complexity of the magmatic system that involved multiple eruptions from one or more sources. Hydrated volcanic fragments in hyaloclastic rocks, and the presence of a sequence of shallow and intermediate-depth marine microfossils, suggest that the Middle Eocene units were erupted in a marine basin. The bimodal volcanism of the Late Eocene is distinguished by the presence of four alternating sequences of hyaloclastite lava and ignimbrite. The REE patterns show spatial homogeneity and temporal heterogeneity in the composition of all the Late Eocene sequences, suggesting origination of magma from varying sources that erupted at different times. The trace element distributions of the hyaloclastites and ignimbrites are compatible with those evolved through fractional crystallization of the lower and upper continental crust, respectively.

Volatile elements released from the subducting slab play a fundamental role during the formation of arc magmas in the mantle wedge. Advances of melt inclusion studies enlarged the data on volatile abundance in arc magmas, and it is now possible to characterize some volatile contents in arc primary magmas, in particular F and Cl. A recent study of Mt Shasta melt inclusions (LeVoyer et al., 2010) shows that fractionation of F and Cl potentially contains information about arc magma genesis. In order to trace the source of arc magmas, fluorine and chlorine partitioning was investigated. Here, I present new experimental determinations of Cl and F partition coefficients between dry and hydrous silicate melts and mantle minerals: olivine, orthopyroxene, clinopyroxene, plagioclase, garnet and also pargasite and phlogopite. The values were compiled from more than 300 measurements in 24 melting experiments, conducted between 8 and 25 kbars and between 1180 and 1430˚C. The low abundance F, Cl measurements in minerals were done by Cameca IMF 1280 at WHOI using the negative secondary ion mode. The results show that DOpx/meltF ranges from 0.123 to 0.021 and DCpx/meltF ranges from 0.153 to 0.083, while Cl partition coefficient varies from DOpx/meltCl from 0.002 to 0.069 and DCpx/meltCfrom 0.008 to 0.015, as well. Furthermore, DOl/meltF ranges from 0.116 to 0.005 and DOl/meltCl from 0.001 to 0.004; DGrt/meltF ranges from 0.012 to 0.166 and DGrt/meltCl from 0.003 to 0.087 with the increasing water amount and decreasing temperature. I also show that F is compatible in phlogopite DPhl/meltF > 1.2) while DAmp/meltF is incompatible in pargasite DAmp/meltF from 0.36 to 0.63). On the contrary, Cl is more incompatible in phlogopite (DPhl/meltCl > 1.2 on average 0.09 ± 0.02), than in pargasite (DPhl/meltCl from 0.12 to 0.38). This study demonstrates that F and Cl are substituted in specific oxygen site in minerals that lead then to be more sensitive than trace elements to crystal chemistry and water amount variations thus melting conditions. Using those new partition coefficients, I modelled melting of potential sub-arc lithologies with variable quantity aqueous-fluid. This model is able to decipher 1) amount of aqueous-fluid involved in melting, 2) melting induced by fluid or melting of an hydrous mineral-bearing source and 3) melting of either pargasite-bearing lithology or phlogopite-bearing lithology and shows that sources of some primitive melts, for instance from Italy, bear pargasite and phlogopite, while some primitve melts seem to be the results of fluid-induced melts.

This doctoral thesis is devoted to studying the possibilities of using additive manufacturing (AM) and design based on computed tomography (CT), for the production of patient-specific implants within orthopedic surgery, initially in a broad perspective and, in the second part of the thesis focusing on customized clavicle osteosynthesis plates. The main AM method used in the studies is the Electron Beam Melting (EBM) technology. Using AM, the parts are built up directly from 3D computer models, by melting or in other ways joining thin layers of material, layer by layer, to build up the part. Over the last 20 years, this fundamentally new way of manufacturing and the rapid development of software for digital 3D reconstruction of anatomical models from medical imaging, have opened up entirely new opportunities for the design and manufacturing of patient-specific implants. Based on the information in a computed tomography (CT) scan, both digital and physical models of the anatomy can be created and of implants that are customized based on the anatomical models.   The main method used is a number of case studies performed, focusing on different parts of the production chain, from CT-scan to final implant, and with several aims: learning about the details of the different steps in the procedure, finding suitable applications, developing the method and trying it out. The first study was on customized hip stems, focusing on the EBM method and its special preconditions and possibilities. It was followed by a study of bone plates, designed to follow the patient-specific bone contour, in this case a tibia fracture including the whole production chain. Further, four cases of patient-specific plates for clavicle fracture fixation were performed in order to develop and evaluate the method. The plates fit towards the patient’s bone were tested in cooperation with an orthopedic surgeon at Östersund hospital. In parallel with the case studies, a method for finite element (FE) analysis of fixation plates placed on a clavicle bone was developed and used for the comparative strength analysis of different plates and plating methods. The loading on the clavicle bone in the FE model was defined on a muscle and ligament level using multibody musculoskeletal simulation for more realistic loading than in earlier similar studies.    The initial studies (papers I and II) showed that the EBM method has great potential, both for the application of customized hip stems and bone plates; in certain conditions EBM manufacturing can contribute to significant cost reductions compared to conventional manufacturing methods due to material savings and savings in file preparation time. However, further work was needed in both of the application areas before implementation. The studies on the fracture fixation using patient-specific clavicle plates indicated that the method can facilitate the work for the surgeon both in the planning and in the operating room, with the potential of a smoother plate with a better fit and screw positioning tailored to the specific fracture (paper VI). However, a large clinical trial is required to investigate the clinical benefit of using patient-specific plates. The FE simulations showed similar stress distributions and displacements in the patient-specific plates and the commercial plates (papers III to VI).   To summarize: the results of this thesis contribute to the area of digital design and AM in patient-specific implants with broad basis of knowledge regarding the technologies used and areas in which further work is needed for the implementation of the technology on a larger scale. Further, a method has been developed and initially evaluated for implementation in the area of clavicle fracture fixation, including an approach for comparing the strength of different clavicle plates.

The Sutton Chen and quantum Sutton Chen potentials are used in molecular dynamics simulations to describe the structural, thermodynamical, and transport properties of Pd, Ni and their binary alloys in solid, liquid, and glass phases. Static properties including elastic constants, pair distribution function, static structure factor, and dynamical properties consisting of phonon dispersion relation, diffusion coefficient, and viscosity are computed at various temperatures. The melting temperatures for Pd-Ni system are obtained. The transferability of the potentials is tested by simulating the solid and liquid states. The eutectic concentration Pd0.45Ni0.55 is quenched at four different cooling rates. The system goes into glass formation at fast cooling rates, while it evolves to crystal at slow cooling rate. Comparison of calculated structural and dynamical properties with the available experiments and other calculations shows satisfactory consistency.

Selective laser melting (SLM) is an additive manufacturing process which enables the creation of intricate components from high performance alloys. This facilitates the design and fabrication of new cellular materials for blast and impact mitigation, where the performance is heavily influenced by geometric and material sensitivities. Design of such materials requires an understanding of the relationship between the additive manufacturing process and material properties at different length scales: from the microstructure, to geometric feature rendition, to overall dynamic performance. To date, there remain significant uncertainties about both the potential benefits and pitfalls of using additive manufacturing processes to design and optimise cellular materials for dynamic energy absorbing applications. This investigation focuses on the out-of-plane compression of stainless steel cellular materials fabricated using SLM, and makes two specific contributions. First, it demonstrates how the SLM process itself influences the characteristics of these cellular materials across a range of length scales, and in turn, how this influences the dynamic deformation. Secondly, it demonstrates how an additive manufacturing route can be used to add geometric complexity to the cell architecture, creating a versatile basis for geometry optimisation. Two design spaces are explored in this work: a conventional square honeycomb hybridised with lattice walls, and an auxetic stacked-origami geometry, manufactured and tested experimentally here for the first time. It is shown that the hybrid lattice-honeycomb geometry outperformed the benchmark metallic square honeycomb in terms of energy absorption efficiency in the intermediate impact velocity regime (approximately 100 m/s). In this regime, the collapse is dominated by dynamic buckling effects, but wave propagation effects have yet to become pronounced. By tailoring the fold angles of the stacked origami material, numerical simulations illustrated how it can be optimised for specific impact velocity regimes between 10-150 m/s. Practical design tools were then developed based on these results.

In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Diques de basaltos toleíticos de baixo-TiO2 ocorrem na porção oriental do Enxame de Diques da Serra do Mar, na Região dos Lagos, entre Niterói e Búzios. Eles têm direções, preferencialmente, NE-SW, subordinadamente, NNE-SSW e mais raramente, NW-SE, e formas intrusivas variáveis. Os basaltos são holocristalinos a hipocristalinos, inequigranulares a equigranulares, intergranulares e intersertais. Eles são constituídos essencialmente de plagioclásio, augita e/ou pigeonita, com olivina corroída, minerais opacos e apatita como minerais acessórios e biotita, bowlingita, idingisita, uralita e saussurita como minerais secundários. A assembléia de fenocristais destas rochas foi estimada em 15% de olivina, 40% de augita e 45% de plagioclásio. Os rochas inserem-se numa série basáltica subalcalina de afinidade toleítica de baixo-TiO2 pouco expandida (MgO= 8,13-5,91%peso), não tendo sido encontradas amostras representativas de líquidos basálticos primários. Esta suíte predominante foi denominada Suíte Costa Azul. No entanto, os dados litogeoquímicos apontam para a existência de mais que uma suíte de baixo-TiO2 na área de estudo que, segundo modelos de fusão parcial em equilíbrio modal, poderiam ter sido geradas por diferentes quantidades de fusão a partir de uma mesma fonte com granada residual. Em termos regionais, a suíte Costa Azul pode ser relacionada com a Suíte Esmeralda que ocorre na subprovíncia Sul de Paraná-Etendeka, muito embora abrangendo um espectro mais amplo de razões Ti/Y. As rochas da suíte Costa Azul evoluíram por 42% de cristalização fracionada envolvendo uma assembléia de fenocristais composta por 15% de olivina, 40% de augita e 45% de plagioclásio, sem mudança de assembléia fracionante. Misturas de componentes mantélicos empobrecidos (mínimo de 72% de D-MORB) e enriquecidos (máximo de 28% de manto litosférico subcontinental) estão associadas à petrogênese desta suíte. Misturas entre componentes do tipo pluma e litosféricos não conseguem explicar as composições parentais da suíte. Os modelos petrogenéticos permitiram a proposição de um modelo geodinâmico envolvendo delaminação do manto litosférico subcontinental englobado por células convectivas ascendentes do manto sublifosférico subjacente em níveis astenosféricos pouco profundos durante um estágio avançado de rifteamento do supercontinente Gondwana. / Low-TiO2, tholeiitic basalt dykes occur eastwards the Serra do Mar Dyke Swarm within the Região dos Lagos from Niterói up to Búzios city. The dykes strike preferentially NE-SW bearing variable intrusive structures. The basalts are holo- to hypocrystaline, equigranular to inequigranular rocks with mostly intergranular and intersertal textures. They are composed mostly by plagioclase, augite and/or pigeonite and have corroded olivine, opaque minerals and apatite as accessory phases. Secondary mineralas are represented by biotite, bowlingite, iddingisite, uralite and saussurite. The phenocrysts assemblage comprise 15% olivine, 40% augite and 45% plagioclase. The rocks comprise a low-TiO2, subalkaline, tholeiitic basaltic suite hereafter called the Costa Azul suite. Nevertheless, lithogeochemical data point to the existence of more than one low-TiO2 suite in the study area. Geochemical modelling has shown that these suites can be related by different degrees of partial melting from a similar mantle source with residual garnet. The Costa Azul suite can be related with the Esmeralda low-TiO2 basaltic suite within the Paraná-Etendeka CFB province due south Brazil although comprising a wider Ti/Y ratio range. The rocks of the Costa Azul suite evolved by 42% of fractional crystallisation involving a phenocryst assemblage with 15% de olivine, 40% augite and 45% plagioclase. Binary mixing modelling point to at least 72% of a D-MORB component and 28% of a subcontinental lithospheric mantle (SCLM) component in the petrogeneses of the Costa Azul basalts. Models involving mixing between plume-like asthenospheric and SCLM components cannot explain the geochemistry of parental liquids in the Costa Azul suite. A geodynamic model involving continental lithosphere delamination and entrainment by ascending convection cells from the underlying asthenospheric depleted mantle during an advanced stage of Gondwana rifting is depicted on the basis of the petrogenetic models proposed for the Costa Azul suite.

Made available in DSpace on 2016-06-02T20:16:43Z (GMT). No. of bitstreams: 1 1968.pdf: 1149213 bytes, checksum: 8acdd67fec9e555998a18561b9fbf007 (MD5) Previous issue date: 2008-07-23 / Financiadora de Estudos e Projetos / A study about surface melting on silver using equilibrium molecular dynamics simulation is the proposal of this work. We applied the Embedded Atom Method as the many-body interaction potential to describe Ag properties. Simulations were done in the microcanonical ensemble, for the study of bulk properties, and in the canonical ensemble, for simulations of the solid with surfaces. As a preliminary result, we obtained the equilibrium melting point Tm equal 1264(12)K from solid-liquid coexistence configurations. Surfaces were simulated using repeated slabs separated by vacuum in the z direction, while keeping periodic boundary conditions in the remaining directions. Results showed that Ag[110] is the lone orientation that has surface melting. Ag[111] maintains its crystalline structure even after reaching Tm, while it could be overheated by 100K. Other properties like density of states, thermal expansion and surface relaxation were in good agreement with experimental data. / Um estudo sobre a fusão de superfícies da prata (Ag) utilizando dinâmica molecular de equilíbrio é a proposta deste trabalho. Aplicamos o método Embedded Atom como potencial de interação de muitos corpos para descrever as propriedades da prata. As simulações foram feitas nos ensembles microcanônico, para o estudo de propriedades de bulk, e canônico, para as simulações do sólido com superfícies. Como resultado de estudo preliminar, obtivemos a temperatura de fusão de equilíbrio Tm igual a 1264(12)K a partir das configurações do sistema com as fases sólida e líquida em coexistência. As superfícies foram simuladas incluindo uma separação com vácuo acima e abaixo do cristal na direção z e utilizando condições periódicas de contorno nas outras direções cartesianas. Os resultados mostraram que a superfície [110] é a única que possui fusão de superfície. A superfície [111] mantém sua estrutura cristalina até mesmo após atingir Tm, podendo esse sistema ser superaquecido em 100K. Outras propriedades como densidade de estados, dilatação térmica e relaxação de superfície tiveram boa concordância com os dados obtidos experimentalmente.