Caracteres estruturais e dimensão fractal da folha de espécies de Arachis e sua relação com a cercosporiose

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Análise do comportamento fractal da propagação de trinca por fadiga em aço 300M e liga de alumínio AA7475

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fractografia quantitativa: análise do comportamento fractal de fratura em compósitos carbono/epóxi, por processamento digital de imagens

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fractografia quantitativa: análise do comportamento fractal da fratura por explosão hidrostática em cilindros de aço sem costura

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fractografia quantitativa: relações entre tenacidade e o comportamento fractal em ligas metálicas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estrutura de variabilidade espacial e temporal da emissão de CO2 e atributos do solo caracterizada por dimensão fractal em área de cana-de-açúcar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Metodologias para estimativa da dimensão fractal do crescimento de aglomerados urbanos: uma contribuição ao estudo da expansão urbana da região metropolitana de São Paulo entre 1905 e 2001

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise histológica, histométrica e fractal de enxerto ósseo autógeno, em elevação de seio maxilar: estudo clínico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo comparativo dos resultados de enxertos de vidro bioativo e osso autógeno, associados ou não ao plasma rico em plaquetas, em seio maxilar de coelho: análise fractal, densitométrica e histomorfométrica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fractografia quantitativa: correlação entre dimensão fractal e tenacidade à fratura em compósitos fibra de carbono/epóxi

The fracture surfaces express the sequence of events of energy release due to crack propagation by linking the relief of the fracture to the loading stresses. This study aims to evaluate the heterogeneity of the critical zone for the advancement of the crack along its entire length in a thermoset composite carbon fiber and epoxy matrix, fractured in DCB testing (Double Cantilever Beam) and ENF (End-Notched Flexure). Investigations were made from image stacks obtained by optical reflection of extended depth from focus reconstruction. The program NIH Image J was used to obtain elevation map and fully focused images of the fracture surface, whose topographies were quantitatively analyzed. The monofractal behavior for DCB samples was assessed as being heterogeneous along the crack front and along the crack for all the conditionings. For the samples fractured in ENF test, there was a strong positive correlation to the natural condition, considering the fibers at 0° for the monofractal dimension and structural dimension (Df and Ds). For fibers at 90° to crack propagation, there was a moderate positive correlation for the textural dimension of natural condition. However, for the samples under ultraviolet condition and those subjected to thermal cycles, there was no correlation between the fractal dimension and fracture toughness in mode II

Análise fractal de fraturas em regime linear elástico: modo I de carregamento

For the development of this graduate work of fractal fracture behavior, it is necessary to establish references for fractal analysis on fracture surfaces, evaluating, from tests of fracture tenacity on modes I, II and combined I / II, the behavior of fractures in fragile materials, on linear elastic regime. Fractures in the linear elastic regime are described by your fractal behavior by several researchers, especially Mecholsky JJ. The motivation of that present proposal stems from work done by the group and accepted for publication in the journal Materials Science and Engineering A (Horovistiz et al, 2010), where the model of Mecholsky could not be proven for fractures into grooved specimens for tests of diametric compression of titania on mode I. The general objective of this proposal is to quantify the distinguish surface regions formed by different mechanisms of fracture propagation in linear elastic regime in polymeric specimens (phenolic resin), relating tenacity, thickness of the specimens and fractal dimension. The analyzed fractures were obtained from SCB tests in mode I loading, and the acquisition of images taken using an optical reflection microscope and the surface topographies obtained by the extension focus method of reconstruction, calculating the values of fractal dimension with the use of maps of elevations. The fractal dimension was classified as monofractal dimension (Df), when the fracture is described by a single value, or texture size (Dt), which is a macroscopic analysis of the fracture, combined with the structural dimension (Ds), which is a microscopic analysis. The results showed that there is no clear relationship between tenacity, thickness and fractal values for the material investigated. On the other hand it is clear that the fractal values change with the evolution of cracks during the fracture process ... (Complete abstract click electronic access below)

Comportamento fractal de superfície da zona de estiramento em aço 300M temperado

Fracture surfaces are the fracture process marks, taht it is characterized by energy release guieded by failure mode. The fracture toughness express this energy em stress and strain terms in pre-cracked samples. The strectch zone is the characteristic region forms by the transition of fatigue fracture and final fracture and it width demonstrate the relation with failure energy release.The quantitative fractography is a broadly tool uses in failure surfaces characterization that it can point to a material’s aspect or a fracture process. The image processing works like an investigation tool, guinding a lot of studies in this area. In order to evaluate the characterization effectivity and it respectivity studies, it used 300M steel that it was thermal treated by an aeronautical process known and it characterized by tensile test and energy dispersive spectroscopy (EDS). The tensile test of this material, made by ASTM E8, allowed the head treatment effectivity confirmation, beyond of mechanics porperties determination. The EDS confirmed the material composition, beyond of base the discussion about fracture mechanism presence. The fracture toughness test has also made, that it works to obtain the fracture surfeaces studies below self-similarity and self-affinity approaches. In front of all the exposed it was possible to conclude that the fractal dimension works like a study parameter of fracture process, allowinf the relation of their values with changes in thickness, which interferes directly in material’s behaviour in fracture toughness approach

Comportamento fractal de superfícies de fadiga em ligas aeronaúticas

Fracture surfaces express sequences of events of energy release with crack propagation in metal alloys, the evolution of topographic features can indicate the lines of load action, failures during the use or processing. The quantitative fractography is an important tool in the study of fracture surfaces, because it allows their interpretation and characterization. In order to evaluate the effectiveness of the characterization of fracture surfaces grounded on concepts such as selfsimilarity and self-affinity, it used the 15-5PH steel that was characterized by metallographic and tensile tests. The metallography allows the microstructural characterization of this steel and proved the presence of the martensite phase in the slats form and a fine-grained, both in the radial and in the axial direction of the dowel. The tensile test (ASTM E8) of this material allowed the determination of the mechanical properties, so based on the obtained results it was possible to affirm that the 15-5PH steel has high mechanical properties and a good stretch. Besides, the specimens also underwent testing of crack propagation, standardized by ASTM E647-00, thus it was obtained the fracture surfaces for characterization under monofractal and multifractal approaches. In front of all the exposed it was possible to conclude that in all measurements the correlation between the crack tip position and the fractal dimension was established in accordance with changes in the thickness and in the fracture micromechanisms presents. Furthermore, the multifractal approach was more sensitive to these variations allowing a more detailed characterization of the morphology

Mass and surface fractal in supercritical dried silica aerogels prepared with additions of sodium dodecyl sulfate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aplicações médicas das abordagens complexas não lineares: a geometria fractal do EEG

Pós-graduação em Saúde Coletiva - FMB