Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

The ACPD method is probably the most versatile of all the commercially available NDE techniques. However as applications of such systems increase so does the awareness of serious limitations in present ACPD knowledge. In particular high local crack and notch tip strains can have a marked effect on ACPD response leading to substantial errors in estimates of crackdepth and growth rates. In the present study an investigation has been undertaken into the influence of elastic/plastic notch tip strain on the response of ACPD crack monitoring systems. Experimental work has been undertaken to produce data on the ACPD response observed in two magnetically contrasting materials (EN1A mild steel, NE8 aluminium alloy) using a series of V and U notched bend specimens. An extensive elastic/plastic finite element analysis was conducted to accurately determine the different notch tip strain fields for both materials. A fundamental study was also undertaken into the influence of strain on the electrical resistivity and relative magnetic permeability, the two material parameters governing the ACPD response. The information obtained from the investigations together with results from the FE analysis has made it possible to understand and quantify the influence of elastic/plastic deformation on ACPD response. An electric field model has been successfully developed to explain and predict the effect of increasing strain on the ACPD response in materials where the skin effect is strong. Results have also shown the inapplicability of the compensation method of crack monitoring when levels of plasticity are appreciable and an alternative method has been proposed.

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Submitted by Heitor Rapela Medeiros (heitor.rapela@ufpe.br) on 2015-03-05T14:05:26Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Perfil de Adolescentes e Jovens Usuários de crack - Ana Luzia Medeiros.pdf: 1687091 bytes, checksum: d15063b0e4cda430e301b97336f0d60b (MD5) / Made available in DSpace on 2015-03-05T14:05:26Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Perfil de Adolescentes e Jovens Usuários de crack - Ana Luzia Medeiros.pdf: 1687091 bytes, checksum: d15063b0e4cda430e301b97336f0d60b (MD5) Previous issue date: 2012 / O consumo de substâncias psicoativas vem aumentando ao longo dos tempos, principalmente quando relacionado às substâncias ilícitas. Dentre estas, destaca-se o crack, reconhecida como a mais agressiva e com maior poder de causar dependência, devido ao elevado potencial aditivo pela peculiar combinação de efeitos farmacológicos e socioculturais implicados em seu uso tornando-se assim, problema mundial de saúde pública. Os adolescentes, caracterizados pela vulnerabilidade intrínseca dessa fase, tornam-se propensos ao uso do crack. Frente ao aumento do seu uso em diferentes cidades do Brasil, esta dissertação está estruturada de acordo com as normas do Programa de Pós-Graduação em Enfermagem da Universidade Federal de Pernambuco - Mestrado Acadêmico com quatro capítulos, sendo um artigo de revisão integrativa e um artigo original. Apresenta como objetivo geral analisar o perfil de adolescentes e jovens usuários de crack à luz da Teoria da Intervenção Práxica e Enfermagem em Saúde Coletiva. Para o artigo de revisão foi realizada a busca de informações na Biblioteca Virtual em Saúde (BVS), resultando em 11 artigos selecionados segundo os critérios de inclusão estabelecidos e submetidos a posterior análise. Os resultados mostram a predominância de jovens entre os consumidores do crack, configurando problema social e de saúde pública, evidenciando a necessidade de redirecionamento das ações de saúde. O artigo original é um estudo descritivo, transversal, do tipo documental, com abordagem quantitativa. Os dados foram coletados nos prontuários dos dependentes de crack, em tratamento nos Caps-AD, Caps-Transtorno e Caps-Infantil do município de Camaragibe/PE.. A coleta de informações foi realizada por meio de um formulário estruturado, adaptado a partir do documento usado pelo serviço para registro das admissões e acompanhamentos clínicos com a totalidade dos casos de dependência do uso de crack entre adolescentes e adultos jovens. Os dados são apresentados sob a forma de médias e frequências, mostrando o perfil caracterizado principalmente por indivíduos do sexo masculino, baixas condições socioeconômicas e padrão grave de consumo da droga. Com base no perfil encontrado, foi elaborado plano de intervenção contendo ações educativas voltadas para adolescentes e jovens usuários de crack bem como àqueles que se encontram em situação de vulnerabilidade. ações preventivas e educativas voltadas para o público jovem podem se mostrar um recurso valioso para a diminuição da incidência do uso de crack nessa faixa etária. Essas ações podem, inclusive, iniciar em fases anteriores como, por exemplo, na infância, fazendo com que os futuros adolescentes e jovens reconheçam os malefícios que as substâncias psicoativas trazem ao seu organismo, às pessoas que lhe cercam e à sociedade.

Non-destructive evaluation is concerned with the detection and characterisation of flaws. In eddy-current inspection, measurements of the electro-magnetic field are made at the surface of a flawed conductor, in an oscillating electric or magnetic field. The aim of this study is to develop an eddy-current method of imaging flaws based on measurements of the magnetic field data. In the presence of an oscillating current, it is shown that the physical behaviour of a thin crack can be modelled by a layer of electric dipoles. Green's functions are introduced, relating the dipole distribution on the crack to the magnetic field above the conductor. It is shown how the resulting integral expressions can predict the magnetic field. These relationships also provide a means of deducing the dipole density on a crack from measurements of the magnetic field. The distribution of dipoles reflects the crack geometry and essentially represents an image of the crack. A scanning rig is described and optimised for use in the study. Alternating current, at a pre-selected frequency (typically around 1kHz), is injected into aluminium alloy plates containing manufactured slots, and spatially distributed measurements of the magnetic field are made with a Hall transducer. The Hall transducer has advantages over traditional coil type transducers, in particular having better spatial resolution and improved detection efficiency, over the range of frequencies used in this study. The dipole density is generally a vector quantity and the problem of recovering it is ill-posed. However, by orientating the plane of the slot perpendicular to the direction of a uniform incident field, it was possible to induce only one component of the dipole density and then recover this from field measurements. The data collected by the experimental rig was used to image two types of manufactured slot. Initially, relatively shallow surface-breaking slots were imaged. For surface cracks, the imaging process was formulated as one of deconvolution, and a Wiener filter was used to perform this operation, to overcome the effects of experimental noise. Secondly, images were obtained of thin slots, which did not break the surface of the conductor, and whose plane extended into the specimens. For these sub-surface slots, the imaging problem was formulated as one of matrix inversion and several techniques were tested for their suitability to invert large ill-conditioned systems, relatively quickly and reliably. The favoured inversion techniques were singular value decomposition (SVD) and a recently developed bi-diagonalisation algorithm known as the Jones-Lanczos (JL) algorithm. The JL algorithm seems a promising technique for the inversion of large, ill-conditioned systems, particularly if noise is present. It is robust and relatively fast, performing the same inversion in one-third the time taken by SVD. Existing conjugate gradient algorithms were also tested, but were found to be inadequate for the solution of the current problem. Dipole images of the two classes of slot were obtained. The images allowed good estimation of geometry and position of the respective slot. Reconstruction of the dipole density on a crack would appear to be an effective method for imaging cracks.

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