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- Multiscale stress analysis in CFRC using microscope image data of carbon fibresPublication . Graça, R. J. R.; Rodrigues, José Alberto; Loja, Amélia; Jorge, PedroComposite materials, are known as strong candidates to improve different kinds of structures. The micromechanical study of these materials is very important, because it may define the best composite characteristics to be used and/or predict more accurately its response. In the present work a multi-stage procedure comprising different fibre contour modelling strategies and a sequent hierarchic multiscale analysis is performed. With this study it is intended to achieve a more realistic characterization of the stresses maximum values for a set of case studies, through the use of fibre geometry data obtained from microscope images of carbon fibre laminated composites. The theoretical circular cross-section is also considered to enable a comparative study among the different situations.
- Image driven analysis of plates coated by cold spray coating process using a layerwise approachPublication . Mota, A. F.; Loja, Amélia; Singh, Harminder; Kalsi, S. B. S.; Barbosa, JoaquimFunctionally graded materials are characterized by its continuous spatial properties' variation which provides them a better behaviour concerning strain and stress transition, hence avoiding the abrupt changes typical of composite fibre reinforced laminates. Although manufacturing systems and techniques used in the production of such materials has evolved significantly, porosities may arise as non-desirable characteristic. Other situations exist where pores are desirable as they may contribute to a specific better performance. Regardless the specific application, it is expected that mechanical properties of graded material will be affected by the existence of porosities. This work presents a study on the static and free vibrations behaviour of plates constituted by a substrate coated by the cold spray coating process. This coating presents inherent porosities which distribution matters to characterize in order to assess its influence on the plate behaviour. To this purpose, a layerwise approach considering the first order shear deformation theory was used, in order to be able to carry out a more representative study of the system substrate-coating. The results obtained show that for a small relation between the coating thickness and the plate's total thickness, the relative deviations obtained, considering the porosity-free coating plate as reference, denotes no evidence of significant influence of the number of terms on the volume fraction approximation, for the static and free vibrations results.
- Photogrametric techniques to health monitoring control of breakwater`s structure using SCILABPublication . Lemos, Rute; Loja, Amélia; Rodrigues, João; Rodrigues, José AlbertoThe need for shelter zones in coastal areas leads to the construction of structures for shore protection such as breakwaters. Its design is mainly made based in semi-empirical formulas [1] [2] [3] and in the experience of the project designer, being the effectiveness of the breakwater carried out through physical modelling. The Harbours and Maritime Structures Division of National Laboratory (NPE, portuguese acronym) for Civil Engineering (LNEC, portuguese acronym) have developed several experiments in bidimensional and tridimensional models. Through this experiments, the stability of the breakwater is tested and the evaluation of damage is made by counting the armor units dislocated (movements or displacements).This damage evaluation is currently done by visual inspection thus being a subjective method where some relevant movements may go unnoticed.
- Finite element techniques for medical image processingPublication . Almeida, A.; Barbosa, Joaquim; Carvalho, A.; Loja, Amélia; Portal, Ricardo; Rodrigues, José Alberto; Vieira, L.We consider some second-order variational model for solving medical image problems. The aim is to obtain as far as possible fine features of the initial image and identify medical pathologies. The approach consists of constructing a family of regularized functionals and to select locally and adaptively the regularization parameters. The parameters selection is performed at the discrete level in the framework of the finite element method. We present several numerical simulations to test the efficiency of the proposed approach.