For a large mixed-mode database, how to discretize its continuous data into interval events is still a practical approach. If there are no class labels for the database, we have nohelpful correlation references to such task Actually a large relational database may contain various correlated attribute clusters. To handle these kinds of problems, we first have to partition the databases into sub-groups of attributes containing some sort of correlated relationship. This process has become known as attribute clustering, and it is an important way to reduce our search in looking for or discovering patterns Furthermore, once correlated attribute groups are obtained, from each of them, we could find the most representative attribute with the strongest interdependence with all other attributes in that cluster, and use it as a candidate like a a class label of that group. That will set up a correlation attribute to drive the discretization of the other continuous data in each attribute cluster. This thesis provides the theoretical framework, the methodology and the computational system to achieve that goal.

This thesis refers to a simulation of an adhesive joint used to bond two metal sheets of a component of the side skirt bracket implemented in trucks. The adhesive joint must support fatigue and mixed-mode loading. The principal goal is the implementation of a novel material model, which governs the damage produced by a mixed-mode fatigue loading in a rubber adhesive layer. Two approaches to define the material model are implemented: the filament model and the principal strain model. The models are fitted against experiments, which have been performed parallel to the development of this thesis by the Mechanics of Materials (MoM) research group of the University of Skövde. The models incorporate fitting parameters with the aim of adjusting the models against experimental results. Simulations are performed using the Finite Element (FE) software, ABAQUS, and the material models are implemented using UMAT subroutines. The filament model is inaccurate and it is considered unable to model the mixed-mode behaviour of the adhesive joint. The principal strain model is considered a well-established method to define the damage and to predict the fatigue life of the adhesive under fatigue in mixed-mode loading.

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The objective of this work is to study crack path deflection under proportional and non-proportional mixed-mode fatigue and predict crack branching direction based on linear elastic fracture mechanics (LEFM) driving forces. Under proportional in-phase mixed Mode I / Mode II loading conditions, crack growth direction has previously been observed in some materials to shift from tensile-dominated Mode I to shear-dominated Mode II or mixed-mode crack growth at higher proportions of initial Mode II loading, but non-proportional loads are not well-characterized. An LEFM approach is desired in order to implement the model in crack growth software such as the boundary element-based fracture analysis package FRANC3D. A novel specimen configuration has been designed and analyzed for generation of wide ranges of mixed-mode loading conditions in a single test. This specimen and a more conventional thin-walled tubular specimen have been used to test polycrystalline nickel-base superalloy Inconel 718 under proportional in-phase and 3 kinds of non-proportional fatigue loading. Stress intensity factors for the various configurations have been analyzed with FRANC3D. Modal transition from Mode I (tensile) to Mode II (shear) crack branching has been observed in several load cases. Qualitative microscopy of fracture surfaces was used to characterize the difference between crack branch modes. An LEFM approach based on an effective stress intensity factor range, which incorporates the maximum value and range of each appropriate stress intensity (Mode I or Mode II), has been used to successfully predict the crack deflection angles, and in some cases to quantify modal transition, within each load case considered. Variability between load cases and specimen configurations points to the limitations of LEFM in providing a general predictor of crack path behavior across all types of non-proportional mixed mode loading.

Thin material layers have found various applications with various roles of functions, such as in fibre reinforced laminated composite materials, in integrated electronic circuits, in thermal barrier coating material system, and etc. Interface delamination is a major failure mode due to either residual stress or applied load, or both. Over the past several decades, extensive research works have been done on this subject; however, there are still uncertainties and unsolved problems. This thesis presents the new developed analytical studies on local delamination failure of thin material layers. Firstly, the analytical theories are developed for post-local buckling-driven delamination in bilayer composite beams. The total energy release rate (ERR) is obtained more accurately by including the axial strain energy contribution from the intact part of the beam and by developing a more accurate expression for the post-buckling mode shape. The total ERR is partitioned by using partition theories based on the Euler beam, Timoshenko beam and 2D-elasticity theories. By comparing with independent test results, it has been found that for macroscopic thin material layers the analytical partitions based on the Euler beam theory predicts the propagation behaviour very well and much better than the others. Secondly, a hypothesis is made that delamination can be driven by pockets of energy concentration (PECs) in the form of pockets of tensile stress and shear stress on and around the interface between a microscopic thin film and a thick substrate. Both straight-edged and circular-edged spallation are considered. The three mechanical models are established using mixed-mode partition theories based on classical plate theory, first-order shear-deformable plate theory and full 2D elasticity theory. Experimental results show that all three of the models predict the initiation of unstable growth and the size of spallation very well; however, only the 2D elasticity-based model predicts final kinking off well. Based on PECs theory, the room temperature spallation of α-alumina oxidation film is explained very well. This solved the problem which can not be explained by conventional buckling theory. Finally, the analytical models are also developed to predict the adhesion energy between multilayer graphene membranes and thick substrates. Experimental results show that the model based on 2D elasticity partition theory gives excellent predictions. It has been found that the sliding effect in multilayered graphene membranes leads to a decrease in adhesion toughness measurements when using the circular blister test.

Este trabalho apresenta os principais fenômenos que regem a propagação de trincas em anéis de rolamentos, por meio da aplicação de conceitos da Mecânica da Fratura Elástica Linear e Fadiga. O estado complexo de tensões atuante sobre o anel do rolamento culmina em carregamento modo misto sobre as paredes da trinca. Para o problema de rolamento proposto, são considerados os modos de abertura e de cisalhamento puro no plano do defeito, sob regime cíclico. O fator de intensidade de tensões K e a integral J são parâmetros que estabelecem condições de fratura e são suficientes, para caracterizar a criticidade de trincas instaladas em anéis de rolamentos. A avaliação da criticidade de defeitos é baseada na aplicação de Critérios de Falha distintos, oriundos de literaturas especializadas. A partir dos parâmetros de fratura, K e J , e da avaliação da criticidade de defeitos é possível determinar a vida remanescente à fadiga, por meio de modelos que descrevem a taxa de propagação de trincas. Os resultados indicam que o modo misto de carregamento de trinca considerado na dissertação, é um dos parâmetros mais importantes a considera-se na nucleação e propagação de defeitos em rolamentos, e são responsáveis por uma redução significativa da vida à fadiga originalmente estipulada. / This work presents the main phenomenon that governs the crack propagation in bearing rings, through the application of Linear Elastic Fracture Mechanics and Fatigue concepts. The complex stress state acting on the bearing ring produces a mixed mode loading over the crack faces. The proposed bearing problem considers a tensile mode and pure shear mode in the plane of the defect, both under a cyclic regime. The stress intensity factor K and the J -integral parameters define the fracture conditions and suffice to characterize the severity of cracks developed in bearing rings. The procedure for defect assessment is based on the application of different failure criteria. Using parameters, K and J, coupled to the defect assessment procedures, it is possible to estimate the remaining fatigue life, through models that describe the crack propagation rate. The results indicate that the mixed mode loading considered in this work is one of the most important parameters in nucleation and propagation of bearing defects and are responsible for a significant reduction in the original estimation of fatigue life.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / As mais importantes lactases, em termos de interesse biotecnolÃgico, sÃo aquelas produzidas por leveduras do gÃnero Kluyveromyces, que sÃo intracelulares e, em sua maioria, sÃo obtidas por fermentaÃÃo em cultura submersa. Esta tÃcnica, assim como a maioria dos processos biotecnolÃgicos, envolve a necessidade de purificaÃÃo de proteÃnas e peptÃdeos a partir de uma variedade de fontes. Neste contexto, uma das tÃcnicas mais notavelmente promissoras à a cromatografia de modo misto, que permite interaÃÃes iÃnicas e hidrofÃbicas simultaneamente entre o adsorvente e o adsorbato. O objetivo do presente trabalho foi estudar a viabilidade da recuperaÃÃo e purificaÃÃo da enzima β-galactosidase, produzida por meio de processo fermentativo e utilizando o micro-organismo Kluyveromyces lactis, por tÃcnica de cromatografia de modo misto. OperaÃÃes unitÃrias de precipitaÃÃo proteica e diÃlise foram tambÃm realizadas com o intuito de concentrar a enzima de interesse e eliminar detritos celulares e outros interferentes advindos do meio de fermentaÃÃo, o que ocasionaria uma diminuiÃÃo do rendimento do processo. A produÃÃo se apresentou satisfatÃria, com uma mÃdia de valores de concentraÃÃo de enzimas totais de 0,45 mg/mL, atividade enzimÃtica de 67 U/mL, atividade especÃfica de 167,9 U/mg. O Fator de PurificaÃÃo obtido foi de 1,17. Uma precipitaÃÃo seguida de diÃlise foi realizada e a posterior corrida cromatogrÃfica em leito fixo com esse material rendeu valores de recuperaÃÃo de 41,0 e 48,2% de proteÃna total e atividade total, respectivamente. A anÃlise de eletroforese SDS-PAGE confirmou a evoluÃÃo do processo de purificaÃÃo no decorrer das operaÃÃes unitÃrias, atestando a viabilidade do emprego das tÃcnicas utilizadas para obtenÃÃo de enzimas com considerÃvel grau de pureza com alto valor comercial agregado. / The most important lactases, as far as biotechnological interest is concerned, are those produced by Kluyveromyces yeasts, which are intracellular and currently obtained mostly by submerged-state fermentation. This technique, just as the mainstream biotechnological processes, involves a need for protein and peptide purification from a variety of sources. In this context, one of the most promising notable techniques that can be highlighted is Mixed Mode Chromatography, which allows simultaneous ionic and hydrophobic interactions between the adsorbent and the adsorbate. Thus, the aim of this work was to assess the feasibility of recovery and purification of a Kluyveromyces lactis β-galactosidase, produced via fermentation process, by employing Mixed Mode Chromatography. Unit operations, such as protein precipitation and dialysis were also performed in order to concentrate the enzyme of interest and eliminate cell debris and other interferences inherent in the fermentation medium, something that would result in a decrease in the process yield. The production showed satisfactory results, with mean values for total enzyme concentration of 0.45 mg/mL, enzymatic activity of 77 U/mL and specific activity of 167,9 U/mg. The Purification Factor obtained was 1.17. A precipitation step, followed by a dialysis process, was performed and the later chromatographic run carried out in fixed bed with this material yielded recovery values of 41.0 and 48.2% of total protein and activity, respectively. SDS-PAGE Electrophoresis confirmed the purification evolution throughout the unit operations employed, confirming the viability of the employment of the techniques used to obtain an enzyme of considerable degree of purity and possessing high-added value.

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This work focuses on improving the quality of carbon-based core-shell materials for high performance liquid chromatography (HPLC) via the characterization of the core materials, and also the development of chromatographic methods (separations) for them. In the early part of this work, I applied organic synthesis to make uniform, spherical poly(divinylbenzene) (PDVB) microspheres, and then carbonized them to prepare carbon core materials for core-shell particle synthesis. Here, I studied in detail the surface and material properties of these particles with multiple instruments, which allowed me to describe the physical and chemical changes that took place during each treatment. The uniform, spherical carbon core materials greatly improved the efficiency of the previously developed carbon-based core-shell HPLC columns from ca. 70,000 plates per meter (N/m) to ca. 110,000 N/m for various alkyl benzenes. Later, I focused on generating application notes to showcase these mixed-mode HPLC columns. Here, liquid chromatography mass spectrometry (LC-MS) was used for the detection of analytes that lack chromophores for UV detection. In this dissertation, Chapter 1 contains a historical background and theory of HPLC along with a review of the use of carbon-based core-shell materials for elevated pH and temperature applications. Chapter 2 describes the improvement of the efficiency of carbon-based materials for HPLC using carbonized PDVB microspheres as the carbon core material. Chapter 3 is a study on the characterization of carbonized PDVB microspheres with multiple instruments. Chapter 4 describes the separation of cannabinoids using three types of carbon-based mixed-mode HPLC columns. Chapter 5 consists of (i) guidelines for the retention mechanism of the core-shell particles that have been commercialized for chromatography by Diamond Analytics, a US Synthetic Company in Orem, Utah, and (ii) application notes for these columns. Finally, Chapter 6 discusses possible future work.