A load moving on a floating ice sheet produces a deflection of the ice sheet. In this Dissertation, three problems associated with mathematical models of the ice water system are examined. A mathematical model involving a steadily moving rectangular load on an ice sheet where the supporting fluid is of infinite depth is analyzed. The solution is written as a Fourier integral and is estimated using an asymptotic method. The results show that the amplitude of the ice deflection is similar to the case where the supporting fluid is of finite depth. The only significant difference is that, in contrast to the case where the supporting fluid is of finite depth where a quiescent zone appears behind the load when its speed exceeds the speed of gravity waves on shallow water, waves appear behind the load for all supercritical load speeds. A mathematical model of an ice plate that takes into account the thickness of the ice is derived by assuming that the vertical shearing forces vary linearly through the ice plate. The equations obtained are similar to those used to describe a mathematical model using a thin plate approximation subjected to in-plane forces. A comparison of the dispersion relation is carried out between the mathematical model of an ice plate that takes into account the plate thickness, the mathematical model of an ice plate using the thin plate approximation, and the mathematical model of an ice plate using the thin plate approximation subjected to in-plane forces. The results show that taking the ice thickness into consideration decreases the minimum phase speed. However, this effect is small. The major contribution of this Dissertation is the determination of the large time response of the deflection of an ice sheet caused by the steady motion of an impulsively-started point load. The results obtained are new. The solution of the ice deflection is written as a Fourier integral and asymptotic methods are used to estimate the large time behaviour of the rate of change of the ice deflection with respect to time. The large time behaviour of the ice deflection itself is inferred from this estimate. This is done for the full range of load speeds and the results are verified numerically using the Fast Fourier Transform. The results in this Dissertation show that the minimum of the phase speed is the only critical speed, in the sense that no finite steady-state is attainable. At this speed the ice deflection grows logarithmically with time. This is in contrast with the case of a line load where there are two critical speeds: the minimum of the phase speed at which the ice deflection grows as the square-root of time, and the speed of gravity waves in shallow water at which the ice deflection grows as the cube-root of time. For a point load, it is found that the transient part of the ice deflection decays as the cube-root of time when the load speed is the speed of gravity waves in shallow water. The asymptotic estimates also show that the decay or the growth rate of the transient component of the ice deflection does not depend on either the relative orientation of the observation point and the load or on the distance between the load and the observation point. / Graduate

Orientador: Mauro Augusto Demarzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-14T09:00:15Z (GMT). No. of bitstreams: 1 Bastos_EliomarFerreira.pdf: 3080328 bytes, checksum: 481f3a6626b449c04574604587e82d3b (MD5) Previous issue date: 2009 / Resumo: Dentre os painéis derivados de madeira de reflorestamento, o OSB (Oriented Strand Board), que possui uma considerável resistência, e que, portanto, é indicado para construção civil, vem apresentando crescimento em sua produção. Neste contexto, o objetivo deste trabalho é apresentar aspectos específicos importantes a serem observados em pesquisas laboratoriais de algumas propriedades físicas e mecânicas desse material. Como resultado esperado, além dos resultados obtidos para chapas de OSB de 17 mm, plastificada e não plastificada, prevê-se a identificação de recomendações que sejam úteis para a implantação de uma sistemática visando a normatização desses ensaios. Por falta de normatização brasileira específica para OSB, se fez necessárias adaptações das prescrições experimentais das normas brasileiras (ABNT) para Compensados e para Madeiras Aglomeradas, bem como de normas estrangeiras voltadas ao OSB: Normas Canadense para OSB (CSA), Normas Européias para OSB (NP-EN), e Normas Americanas para OSB (ASTM). / Abstract: Amongst the panels derived wooden from reforestation, OSB (Oriented Strand Board), that it possesses a considerable resistance, and that, therefore, it is indicated for civil construction, it comes presenting growth in its production. In this context, the objective of this work is to present specific aspects important to be observed in laboratories research of some physical and mechanical properties of this material. As waited result, beyond the results gotten for plates of OSB of 17 mm, plasticized and not plasticized, it is foreseen identification of recommendations that are useful for the implantation of a systematic aiming at the standardization of these assays. Due to specific Brazilian standardization for OSB, if it made necessary adaptations of the experimental lapsing of the Brazilian norms (ABNT) for Compensated and Agglomerated Wood, as well as of come back foreign norms to the OSB: Standard Canadian for OSB (CSA), European Norms for OSB (NP-EN), and Standard American for OSB (ASTM). / Universidade Estadual de Campi / Estruturas / Mestre em Engenharia Civil

Orientadores: Eder Lima de Alburquerque, Paulo Sollero / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-14T09:43:07Z (GMT). No. of bitstreams: 1 Santana_AndrePereira_M.pdf: 7222618 bytes, checksum: bdf2ef461db36640bbac335c4317c1ae (MD5) Previous issue date: 2008 / Resumo: Este trabalho apresenta formulações dinâmicas do método dos elementos de contorno para a análise de placas finas anisótropicas. As formulações utilizam soluções fundamentais da elasto-estática e os termos de inércia são tratados como forças de corpo. As integrais de domínio provenientes de forças de corpo são transformadas em integrais de contorno usando o método da reciprocidade dual (DRM) e o método da integração radial (RIM). No DRM, é escolhida uma solução particular e a função de aproximação é obtida usando a equação de equilíbrio. No RIM, quatro funções de aproximação são usadas. São implementados formulações para análise modal e análise transiente de placas finas. Na análise modal, a formulação integral é transformada em um problema de auto-valores e auto-vetores onde os auto-valores estão relacionados às frequências naturais e os auto-vetores são os modos de vibrar. Na análise transiente, a integração no tempo é realizada usando o método de Houbolt. Apenas o contorno é discretizado em todas as formulações implementadas. Os resultados numéricos mostram boa concordância com os resultados disponíveis na literatura e também com resultados do método dos elementos finitos. / Abstract: This work presents dynamic formulations of the boundary element method for the analysis of anisotropic thin plates. Formulations use elastostatic fundamental solutions and inertia terms are treated as body forces. Domain integrals that come from body forces are transformed into boundary integrals using the dual reciprocity boundary element method (DRM) and the radial integration method (RIM). In the DRM, a particular solution is chosen and a approximation function is obtained using the equilibrium equation. In the RIM, four different approximations functions are used. Formulations for modal and transient analysis are implemented. In the modal analysis, the integral formulation is transformed in a eigen-value and eigen-vector problem where the eigen-values are related to natural frequencies and the eigen-values stand for vibration shape modes. In the transient analysis, the time integration is carried out using the Houbolt method. Only the boundary is discretized in all implemented formulations. Numerical results show good agreement with results available in literature as well as finite element results. / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

This thesis deals with the topology optimization of plate and shell structures. The shell structures are modeled as plate-like at facets. Firstly, the formulation of the topology optimization problem is presented in an introductory chapter, which introduces two frequently used topology optimization algorithms (being the optimality criterion and the method of moving asymptotes). Examples of applications are shown, and filtering schemes are introduced. Secondly, the derivation of the finite element formulation and interpolation of plates is presented. Both a shear rigid Kirchoff plate element and a shear flexible Mindlin element are considered. The latter element uses substitute shear strains to overcome locking; hence reduced integration is not necessary, as is normally required when shear flexible plate elements are used in topology optimization. The effect of both element formulations on optimal topology is then illustrated. The results reveal the notable effect of through thickness shear on optimal topolog. Thirdly, a at shell element is constructed by combining the plate elements with a membrane element with drilling degrees of freedom. (The membrane is not discussed in any detail.) To illustrate the topology optimization of shell structures, the so-called Scordelis-Lo roof is then selected as an example problem. The analysis includes an assessment of the effect of eccentric stiffeners or ribs on optimum topology. / Dissertation (Master of Engineering)--University of Pretoria, 2007. / Mechanical and Aeronautical Engineering / unrestricted

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / Includes bibliographical references. / by Samuel Franklin Horton. / Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981.

The concept of load analogy is used in the elastic and elastic-plastic analysis of isotropic circular and annular plates undergoing moderately large deflection. The effects of the nonlinear terms of lateral displacement and the plastic strains are considered as additional fictitious lateral loads, edge moments, and in-plane forces acting on the plate. The solution of an elastic or elastic-plastic Von Karman type plate is hence reduced to a set of two equivalent elastic plate problems with small displacements, namely, a plane problem in elasticity and a linear elastic plate bending problem. The method of finite element is employed to solve the plane stress problem. The large deflection solutions are then obtained by utilizing the solutions of the linear bending problems through an iterative numerical scheme. The flow theory of plasticity incorporating a Von Mises layer yield criterion and the Prandtl-Reuss associated flow rule for strain hardening materials is employed in this approach.

The ability to predict failure of laminated composites in compression has been doggedly pursued by researchers for many years. Most have, to a limited extent, been able to predict failure for a narrow range of laminates. No means, as yet, exist for predicting the strength of generic laminates under various load conditions. Of primary concern has been the need to establish the mode at failure in compression. Even this has been known to vary for fiber and matrix dominated laminates. This study has been carried out to analyze the failure of specimens with a hole made of laminates with various quasi-isotropic stacking sequences. Different stacking sequences are achieved by rotating a [±45/90/0]s stacking sequence laminate as a whole with respect to the loading axis of the specimens. Two- and three-dimensional finite element models, using commercial packages, were generated to evaluate the stresses in the region of the hole. Two different compressive failure prediction techniques based on distinctly different failure modes have been used. The validity of these techniques was measured against experimental data of quasi-isotropic specimens tested. To investigate the applicability of the failure criteria for different laminated composite plates, analyses were repeated for specimens with different stacking sequences resulting from the rotation of the laminate. The study shows the need for the use of three-dimensional analysis of the stress state in the vicinity of the hole in order to be able to accurately predict failure. It also shows that no one mode of failure is responsible for limiting the strength for all laminate orientations but rather the mode changes with change in stacking sequence. The failure of the laminate with a hole was seen to be very sensitive to the stacking sequence. Experimental data presented also shows that the peak strength obtainable from the laminate analyzed, [±45/90/0]s, is going to be in the off-axis configuration rather than on-axis placement of the stacking sequence with respect to the loading direction. / Master of Science

Whereas analytic and experimental investigations of plates subject to lateral vibrations have been rather thorough, the present study is an analytic determination of the various critical frequencies of vertically cantilevered thin elastic rectangular plates vibrating freely within their own planes. Within the restrictions imposed by excluding any motion perpendicular to the face of the plate, the upright edges are free to move in the other two directions, as is the top horizontal edge. Three different base conditions are imposed: • A clamped lower edge; • A lower edge which is freely vibrating transversely in the plane of the wall where the vertical fibers of the wall are fixed at their roots; and • A horizontally freely pulsating lower edge where the vertical fibers of the wall are fixed at their roots. The first two conditions are considered in relation to plate vibrations which are essentially vertical while the first and third conditions are each employed with essentially horizontal plate vibrations. In every case the effect of a uniform load placed along the upper edge is studied. Critical frequencies and associated amplitude coefficients are obtained for various ratios of base length to wall height. The solution, which is presented in tabular and graphic forms, is obtained by using the method of iteration on the Rayleigh-Ritz energy procedure. It is concluded that, for a wall with a clamped base vibrating in accordance with the given stipulations, the fundamental period is proportional to the square root of the face area of the wall. When the base of the wall is vibrating there is only one critical period, and it varies with the height of the wall. The factor of proportionality should take into account the material of which the wall is composed. For designing unframed walls, subjected to dynamic loads in their plane, where the applied shear is to be taken as some constant times the dead load at the base of the wall, the recommended lateral force requirements of the Seismology Committee of the Structural Engineers Association of California, as set forth in 1959, seem adequate as modified above. / Ph. D.

Sound pressure radiating from vibrating structures submerged in fluid, as in the case of a vibrating panel in a submarine hull, is usually undesirable. An optimal control methodology for the suppression of far-field acoustic radiation pressure from submerged structures has been developed by Meirovitch (ref. 1). The linear modal state feedback control law developed implies that the full state (displacements and velocities) is available, perhaps through measurements. However, in practice, it is not always feasible to measure the full modal state vector for feedback. To permit practical implementation of the feedback control law, an optimal stochastic state estimator, or Kalman-Bucy filter, has been developed here for incorporation into the control system design. The development has been specialized to a uniform simply supported rectangular plate. / Master of Science

The influence of tip clearance and angle of attack upon the mid-span unsteady pressure response of a vibrating flat plate was investigated experimentally. Unsteady pressure measurements were taken for a variety of incidence angles, vibration frequencies and tip clearances over a Mach number range of 0.2 to 0.6. It was found that changes in tip clearance had an effect on measured pressure fluctuations at higher angles of attack and larger Mach numbers. It was also observed that the amplitude of the unsteady pressure increased as the incidence angle was increased. The plate was mechanically induced to oscillate in translation, simulating the flISt bending mode. Averaged Fast Fourier Transforms were used to determine pressure oscillation amplitudes and phase lags with respect to the plate motion. / Master of Science