Made available in DSpace on 2014-10-09T12:36:47Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:33Z (GMT). No. of bitstreams: 1 04284.pdf: 1503589 bytes, checksum: 2edbafe6bd5d8ce87342f894ae47bd43 (MD5) / Tese (Doutoramento) / IPEN/T / Escola Politecnica, Universidade de Sao Paulo - POLI/USP

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In this work an attempt has been made to develop theories for finite element static and dynamic stress analysis tailored for use with composite layered plates and shells in this way it was hoped to provide accurate values of the stresses particularly transverse shear stresses through the thickness, and to perform accurate natural frequency analysis by including non-linear effects such as centrifugal stiffening. Initial derivations were based upon first order facet shell element analysis and first order curved shell element analysis. Subsequently, derivations were produced for higher order element analysis. A programming package has been developed based upon the above derivations, and containing a banded solver as well as a frontal solver, capable of analysing structures build up from uniform or variable thickness layers and with a multiple number of layers having constant or variable dimension. Results obtained with the aid of the present package have been compared with results derived from experimental work as well as with results derived from available analytical solutions. Investigations have been carried out for existing compressor blades, made of isotropic material and layered composite material, respectively. The results obtained from the package have been compared with available experimental results produced by RR or carried out at Cranfield. It has been shown that the above mentioned derivations produce comparable results and the package has proved to be reliable and accurate.

Made available in DSpace on 2014-10-09T12:36:47Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:33Z (GMT). No. of bitstreams: 1 04284.pdf: 1503589 bytes, checksum: 2edbafe6bd5d8ce87342f894ae47bd43 (MD5) / Tese (Doutoramento) / IPEN/T / Escola Politecnica, Universidade de Sao Paulo - POLI/USP

Orientadores: Marcio de Moraes, Luciana Asprino / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-13T02:18:28Z (GMT). No. of bitstreams: 1 Lyrio_MarianaCamiloNegreiros_M.pdf: 2393437 bytes, checksum: f0dfbf68baaeb080347c83445d15e1e9 (MD5) Previous issue date: 2009 / Resumo: O propósito neste estudo foi realizar avaliação mecânica e fotoelástica de dois diferentes sistemas de fixação interna rígida (FIR): placas convencionais e placas com sistema de travamento. Para avaliação mecânica foi realizado teste de carregamento linear em réplicas de hemimandíbulas humanas dentadas seccionadas na região de ramo mandibular, representando uma osteotomia sagital, e fixadas com avanço mandibular de 5 mm. No grupo I a fixação foi realizada com placas convencionais e parafusos monocorticais do sistema 2,0mm e no grupo II utilizou-se placas e parafusos monocorticais com sistema de travamento do sistema 2,0 mm. Para análise estatística foram aplicados Anova e teste de Tukey em nível de significância de 5%, os quais demonstraram não haver diferenças entre os grupos I e II nos testes mecânicos. Para os testes fotoelásticos foram confeccionadas hemimandíbulas humanas dentadas em resina fotoelástica, também seccionadas simulando a osteotomia sagital e fixadas com avanço mandibular de 5 mm, com os mesmos grupos utilizados para os testes mecânicos. Em relação à distribuição de tensões, pode-se observar que as mesmas se concentram ao redor dos parafusos, principalmente naqueles próximos à área de osteotomia para ambos os grupos. Dessa forma, pode-se afirmar que os sistemas de fixação utilizando placa e parafusos convencionais ou com sistema de travamento não apresentaram diferenças estatísticas quanto à resistência, e que a maior concentração de forças está nas áreas próximas às osteotomias, consideradas regiões de maior fragilidade após a OSRM. / Abstract: The aim of this study was evaluate the mechanical and photoelastic behavior of two methods of rigid internal fixation (RIF): conventional plates and locking plates. For mechanical tests polyurethane synthetic hemimandible with seccional sagittal ramus split was used, simulating an advancement of 5 mm. The fixation performed on the Group I was a 2.0 mm conventional plates with monocortical screws and fixation used on group II was a 2.0 locking plates with monocortical locking screws. Anova and Tukey tests were applied (P<5) and no statistical differences were noted between the groups. Hemimandibles were made in photoelastic resin with same groups used in mechanical tests and submitted to photoelastical analysis. In relation to tension distribution in photoelastic analysis, the fringes were concentrated around screws, mainly in areas near the osteotomy for both groups. Based in this fact, the conventional and locking fixations systems did not present statistical differences on resistence, and the major forces was concentrated in regions near the osteotomies lines, that considered fragility before sagittal split osteotomy. / Mestrado / Cirurgia e Traumatologia Buco-Maxilo-Faciais / Mestre em Clínica Odontológica

This thesis is concerned with the use of zone plate interferometers for the precise location of position. The thesis begins by discussing the use of the zone plate as an optical component and examines the wavefront aberrations that can occur in higher orders of diffraction. Interferometers applicable to the measurement of position are then reviewed, including interferometers that incorporate optical zone plates as beam dividers and beam combiners. A zone plate interferometer for defining and locating multiple positions in three-dimensions is reported. Here, a three-dimensional array of positions is defined by a two-dimensional array of reflective zone plates. An optical probe containing two zone plates completes the interferometer, and is used to locate the positions. The displacement sensitivity of the probe can be controlled at the optical design stage. The variation of sensitivity with wavefront geometry is explored and expressions are derived for the transverse and axial sensitivity in terms of the conjugates of the illuminating wavefronts. Various wave front configurations were experimented with and the resulting position location patterns recorded. The measured values of sensitivity to displacement are compared to theory. A version of this interferometer was designed and developed by the author, for checking the performance of three-coordinate measuring machines used in engineering metrology. The results of trials with the interferometer, comparing the performance of measuring machines in several government laboratories, are reported. The averaged repeatability of setting, on one optically defined position, was found to be 1 μm in the transverse directions and 6 μm in the axial direction. Resulting from this work, two simple devices for pointing are described. Each uses a pair of zone plates to define an optical axis. In one case, the axis is precisely located by positioning a coherent light source and observing the interference bands generated by the device. In the other, moire bands are observed in incoherent illumination.

Vibration and stability studies have been undertaken on glass fibre reinforced polymer composite unstiffened and stiffened plates to optimise their dynamic properties. Boundary conditions, stiffeners and orthotropy of the material add to the complexity of a mathematical solution and to overcome this problem experimental and analytical studies were undertaken. The former method was carried out by impact hammer and an FFT digital signal analyser and the latter method was undertaken using finite element computer software. The current research concentrated upon the procedures and possible techniques available to optimise the dynamic properties of the plate without introducing weight penalty with the object of achieving an efficient structural performance coupled with an economic design. It has been shown that most of the increase in frequency and critical buckling load was directly related to the increase in stiffness of the stiffener and its position on the plate structure. The mode shapes have provided information regarding the most advantageous position for the setting of the stiffeners; they must be positioned away from nodal lines. The effect of the stiffener was significant for the fully clamped and clamped/free plates where only bending modes of vibration are present. However, for the completely free plates, where both bending and torsional modes of vibration could occur, the effect that the stiffeners have on the torsional modes was minimal. To locate precisely the position of the stiffener may be difficult when the plates are subjected to in-plane compressive loads, because higher order mode shapes may interchange. The mass-saving advantage which has been obtained in this research has shown that the stiffened plates with top-hat stiffeners were seen to have higher natural frequencies, within a specific vibration mode, compared to stiffened plates with rectangular stiffeners (blade).

A general analysis for a simply supported prismatic folded plate structure is presented. A stiffness matrix method is used with the individual plates taken as structural elements. When loads are applied to the structure the solution yields joint deflections and internal plate forces. The exact elasticity theory is used for the in plane or membrane solution and the classical thin plate theory is used for the out of plane or bending solution. By modifying a computer program used for stiffness matrix frame analysis, it is possible to solve a folded plate structure with more than two plates connected at the same joint. This is demonstrated by the solution of an I beam torsion problem, which also provides a check of existing torsion theories. Cylindrical barrel vaults of circular and other sections are analysed as folded plate structures. A study is made of the effect of the shape of the cross section on the shell stress distribution for long, short, thick and thin shells. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Finite element method involving rectangular bar cells capable of imitating elastic action in plane stress and flexure of plates with any value of the Poisson's ratio, is extended to investigation of stability of rectangular plates. This requires formulation of the stability matrix used for solution of the eigenvalue problem, which gives the magnitude of the critical load. Four different examples are solved and the results, compared with the exact values and the available no bar solutions, are found to be good. A brief study is also made of the effect of negative extensional and flexural stiffnesses of the members of the cell and suggestion is made on selection of the desirable range for the values of the aspects ratio of the cell as related to the values of µ. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

A visualization technique is applied to the unsteady separated flow about an autorotatlng flat plate. An unsteady potential model is attempted to predict the pressure loading on the plate as a function of angle of attack. To visualize the flow, a streakline is marked by low density air created by the wake of a heated wire probe. An off-center parabolic mirror Schlieren system detects the density gradient. Due to the highly unsteady nature (in this project, the plate rotates at almost 1,000 r.p.m. for a 10-foot per second freestream velocity) of the flow, high-speed 35mm, single lens reflex shots or 16mm. movie films recorded the image. Timing marks on the movie film provided information of the angular speed of the plate during acceleration to the autorotation speed and at autorotation. The two-dimensional unsteady attached flow model attempts to duplicate the effects of separation by superimposing vortices in the wake, as shown in the flow visualization, and by eliminating terms representing the freestream velocity in the range of 60 to 150 degrees angle of attack. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate