Browsing by Author "Silva, T. A. N."
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- Assessing parametric uncertainty on fibre reinforced composite laminatesPublication . Carvalho, A.; Silva, T. A. N.; Loja, AméliaWhen modeling a composite structure it is important to take into account its greater exposition to parametric variability, when compared to other types of materials more traditionally used. The possibility to tailor composite materials according to specific requisites is simultaneously a source of additional variability, which origin may be associated to material and to geometrical characteristics. Regardless the origin of this variability, they will produce its effect in the structure response, thus it is very important to anticipate them and to quantify them as much as possible. With the present work, it is intended to assess and quantify the influence of geometrical parameters variabilities on the composite structural response. Behind this characterization, linear static analyses were performed, considering that the layers’ thicknesses and fibre orientation angles will be affected by uncertainty. A set of simulations and numerical results are presented and discussed.
- Modelling a Rotating Shaft as an Elastically Restrained Bernoulli-Euler BeamPublication . Silva, T. A. N.; Maia, N. M. M.Industrial rotating machines may be exposed to severe dynamic excitations due to resonant working regimes. Dealing with the bending vibration, problem of a machine rotor, the shaft - and attached discs - can be simply modelled using the Bernoulli-Euler beam theory, as a continuous beam subjected to a specific set of boundary conditions. In this study, the authors recall Rayleigh's method to propose an iterative strategy, which allows for the determination of natural frequencies and mode shapes of continuous beams taking into account the effect of attached concentrated masses and rotational inertias, including different stiffness coefficients at the right and the left end sides. The algorithm starts with the exact solutions from Bernoulli-Euler's beam theory, which are then updated through Rayleigh's quotient parameters. Several loading cases are examined in comparison with the experimental data and examples are presented to illustrate the validity of the model and the accuracy of the obtained values.
- A study on the structural behaviour of FGM plates static and free vibrations analysesPublication . Bernardo, G. M. S.; Damásio, F. R.; Silva, T. A. N.; Loja, AméliaFunctionally graded materials are characterised by a determined spatial composition variation of their phases’ constituents, which enable for a closer suitability of the material properties to the desired mechanical behaviour. Concerning to the engineered construction of these materials, they can be thought as being achieved by considering a continuous variation of their phases and thus of their properties, or by considering a discrete stacking of a sufficient number of layers, in order to ensure a less abrupt variation profile of their properties. Also, depending on the nature of the applications, it may be important to consider a sandwich configuration, where the three-layered constitution may correspond to a functional requisite. With the present work, these two situations will be studied, considering different methodologies based either on a meshless method or on different approaches based on the finite element method. A comparative study of the performance and adequacy of the developed models is carried out through a set of illustrative cases focused on the study of static and free vibrations behaviour of plate structures.