Orientadores: Paulo Sollero, Eder Lima de Albuquerque / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T04:07:05Z (GMT). No. of bitstreams: 1 UsecheVivero_JairoFrancisco_D.pdf: 4442457 bytes, checksum: 707a93966692d7daf8a71f104b9a1bb5 (MD5) Previous issue date: 2007 / Resumo: O objetivo deste projeto é o desenvolvimento de uma ferramenta computacional para 'a an'alise e projeto de estruturas aeronáuticas trincadas e reparadas por placas de materiais compósitos laminadas coladas. As placas metálicas isotrópicas da estrutura aeronáutica serão modeladas pelo método dos elementos de contorno considerando a presença de tensões de cisalhamento nos planos normais á superfície das placas (formulação de Reissner-Mindlin). No modelamento do reparo será usada uma formula¸c¿ao por elementos de contorno para placas anisotrópicas sem considerar a presençaa de tensões de cisalhamento nos planos normais à superfície da placa (formulação do Kirchhoff-Love). A análise será validada com resultados analíticos, numéricos e experimentais disponíveis na literatura e com modelos desenvolvidos pelo método dos elementos finitos / Abstract: The objective of this project is the development of a computational tool for the analysis and design of cracked aeronautical structures repaired by adhesively bonded laminated composites. The isotropic metallic plates of the aeronautical structure will be modeled by the boundary element method considering the presence of shear stresses in planes that are normal to the surface of the plates (formulation of Reisner-Mindlin). In order to model the repair, a boundary element formulation for anisotropic plates will be used neglecting the presence of shear stresses in planes that are normal to the surface of the plate (formulation of Kirchhoff-Love). The analysis will be validated with analytical, numerical and experimental results avalilable in the literature and with finite element models / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

This thesis is about using structural-dynamics based methods to address the existing challenges in the field of Structural Health Monitoring (SHM). Particularly, new structural-dynamics based methods are presented, to model areas of damage, to do damage diagnosis and to estimate and predict the sensitivity of structural vibration properties like natural frequencies to the presence of damage. Towards these objectives, a general analytical procedure, which yields nth-order expressions governing mode shapes and natural frequencies and for damaged elastic structures such as rods, beams, plates and shells of any shape is presented. Features of the procedure include the following: 1. Rather than modeling the damage as a fictitious elastic element or localized or global change in constitutive properties, it is modeled in a mathematically rigorous manner as a geometric discontinuity. 2. The inertia effect (kinetic energy), which, unlike the stiffness effect (strain energy), of the damage has been neglected by researchers, is included in it. 3. The framework is generic and is applicable to wide variety of engineering structures of different shapes with arbitrary boundary conditions which constitute self adjoint systems and also to a wide variety of damage profiles and even multiple areas of damage. To illustrate the ability of the procedure to effectively model the damage, it is applied to beams using Euler-Bernoulli and Timoshenko theories and to plates using Kirchhoff's theory, supported on different types of boundary conditions. Analytical results are compared with experiments using piezoelectric actuators and non-contact Laser-Doppler Vibrometer sensors. Next, the step of damage diagnosis is approached. Damage diagnosis is done using two methodologies. One, the modes and natural frequencies that are determined are used to formulate analytical expressions for a strain energy based damage index. Two, a new damage detection parameter are identified. Assuming the damaged structure to be a linear system, the response is expressed as the summation of the responses of the corresponding undamaged structure and the response (negative response) of the damage alone. If the second part of the response is isolated, it forms what can be regarded as the damage signature. The damage signature gives a clear indication of the damage. In this thesis, the existence of the damage signature is investigated when the damaged structure is excited at one of its natural frequencies and therefore it is called ``partial mode contribution". The second damage detection method is based on this new physical parameter as determined using the partial mode contribution. The physical reasoning is verified analytically, thereupon it is verified using finite element models and experiments. The limits of damage size that can be determined using the method are also investigated. There is no requirement of having a baseline data with this damage detection method. Since the partial mode contribution is a local parameter, it is thus very sensitive to the presence of damage. The parameter is also shown to be not affected by noise in the detection ambience.