|Prof. Nuno Maia,
Technical University Of Lisbon
Instituto Superior Tecnico
Dept. Mech. Eng.
Nuno Manuel Mendes Maia obtained his first degree in 1978 and his master's degree in 1985, both in mechanical engineering from Instituto Superior Tecnico (IST), University of Lisbon. He received his PhD in mechanical vibrations (1989) from Imperial College London, UK. He had his habilitation in mechanical engineering in 2001 from IST, University of Lisbon. Prof. Maia has authored and co-authored two textbooks and more than a hundred and sixty scientific publications in international journals and conference proceedings on the subject of modal analysis and structural dynamics.
He is an associate editor of the Shock and Vibration Journal and of the Journal of Vibration and Control, a member of the Society for Experimental Mechanics (SEM), of the International Institute of Acoustics and Vibration (IIAV), and of the Portuguese Society of Acoustics (SPA), where he is responsible for the area of vibrations.
He has participated and coordinated various national and international research projects and has been responsible for the organization of the International Conference on Structural Engineering Dynamics (ICEDyn), since 2002.
His current research interests are modal analysis/testing, updating of finite element models, coupling and structural modification, damage detection, modeling of damping, transmissibility in multiple degree-of-freedom systems, and force identification.
An Overview of Modal Analysis:
Recent Advances on Classical Topics
Modal Analysis and Modal Testing have evolved enormously since the early seventies until nowadays, with the advance of digital computers, analyzers and all sorts of measuring equipment. Initially, a lot of effort was directed towards the development of identification techniques, a research area that today is not very active anymore, as most of the techniques have reach a mature state and one can find the best ones commercialized by the industry. Other topics have emerged and the initial restrict concept of modal analysis associated to system identification has been enlarged and that is the way that we should face it, encompassing a huge variety of subjects, like coupling of substructures, modeling of joints, nonlinear behavior, updating techniques, variability versus uncertainty, damage identification, modeling of damping, transmissibility, force identification, rotor-dynamics, laser techniques, vibro-acoustics, just to name a few. All of these subjects and many more can be addressed from the point of view of modal analysis and modal testing and all of them keep active. The main reason for such an interest and activity relies on the fact that, inspite of all the research that is produced in the various domains, there are subjects that remain open because there are some issues here and there that have not been entirely and satisfactorily solved. An example of this is the proper modeling of joints: when one has a very complex structure to model, the usual approach is to subdivide it in substructures, each of which can be modeled to a very high degree of accuracy, either using numerical tools (or even analytical ones) or through an experimental way, i.e, in an inverse sense; however, even with such an accuracy at each substructure level, when it comes to couple all of the parts together, the comparison between the experimental results of the whole structure and the predictions from the model may reveal large discrepancies. This is due to the fact that wrong assumptions and therefore wrong models have been used to represent the behavior of the connecting joints. These type of components can be particularly difficult to model, due to their complex geometry, complex material behavior, or both. One may be talking about (i) welded, riveted or bolted joints, normally assumed in the numerical model as totally rigid, when in fact they always allow for some flexibility or (ii) more complex situations, where one may be dealing with visco-elastic materials of complex geometry and nonlinear behavior, seals, journal or roller bearings, etc.
Many other topics are recurrently revisited, like force identification, measurement or estimation of rotational degrees of freedom, coupling and uncoupling techniques, with their numerical difficulties, etc. In the present talk, some of these matters are discussed and some recent progresses are reported, namely those related to the detection of damage, the transmissibility in multiple degree of freedom systems, force identification and model updating.