5th International Conference on Acoustics and Vibration

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.

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.

Göran has a Master of Science degree in Technical Physics with material science, mechanics and structural mechanics as special subjects. He has worked with product development, dynamics of mechanical systems as well as dynamics of structures. He has worked with stability problems such as buckling of structures, non-linear analysis involving large deformations, contact between bodies, plasticity in metallic materials and analysis of rubber.
Some of Göran work experiences are as follows:
- ASEA Central Department, R&D Group: He worked with simulations of vehicle dynamics (car-body modes of vibration) of the Swedish passenger coach A7/B7.
- ASEA Traction: He followed the “AEM-7 locomotive project” to ASEA Traction where he was responsible for the car-body strength and dynamics of the commuter train X10 and the articulated tram M21 for Gothenburg. During his time with ASEA Traction, he held a speech at the Technical University in Graz in Austria on the AMTRAK – AEM7 project. The title of the speech was “AMTRAK – 200 km/h in den Vereinigten Staaten mit ASEA-Thyristorlokomotiven”.
- FEM-Tech AB: This company was working with the state-of-the-art finite element programme ABAQUS. He worked with non-linear finite element analysis such as analysis of residual stresses in rolled tubes in steam generators for Swedish nuclear power plants.
- TD Rail & Industry: He worked on project to develop measuring devices for Bombardier Transportation. The objective of the project was to verify that gear is capable to take the dimensioning torque to use in measuring equipment for testing of London Underground Metro cars prior to the Olympic Games 2012.
He also carried out different projects such as:
• He designed all mechanical structures for development of under-ground sub stations for Viken Nett in Norway.
• He was the Technical Director of Nowait Transit some years for development of a train for big cities.
• He started mass production in China for development of a remotely operated electric load breaker.
• He participated in the start of production of special breaker used in electric power distribution systems in the south of China.
• He has worked with analysis of structures for semi-submerged wind power stations.
• He made the design of the lens and the mechanics for development of a special lamp for airports.

Vehicle dynamics of passenger coaches and EMU’s are important for many reasons. Beside the vehicle-track interaction, that has to do with safety and homologation of the vehicle, ride quality and some noise related characteristics can be analysed. The dynamic properties of high speed coaches must be considered with respect to the characteristics of the bogies. The design philosophy with respect to frequency separation and the class of carbody eigenmodes to be considered will be addressed. A short film will be shown.
Carbody dynamic properties are related to ride quality, contents of infra-sound and noise. Early work on ride quality resulted in the design of a comfort index Wz. Carbody vibrations of frequencies in the range 5 – 7 Hz are considered to give more discomfort than other frequencies. This frequency range may co-inside with rigid body frequencies of bogie frames and the possibility to excite carbody eigenmodes.
Modes of vibration in carbodies for railway passenger coaches and EMU’s always have a significant contents of cross sectional vibrations. The simplest description of the cross section mode would be that it could be called a four-node mode shape where the floor and roof go towards the centre of the carbody and the walls go outwards. The side sills and the cant rail could be considered to be “nodes”. The eigenfrequency found is often below 20 Hz and the correlation to infra-sound contents is obvious. The dynamic aspects of sleeper frequent vibrations in railway passenger coaches and EMU’s will be addressed. Excitation of eigenmodes in bogie frames can have consequences for noise inside the passenger compartment.
The problem is quite obvious when the frequencies co-inside with frequencies of standing waves inside the passenger compartment. The room dimensions inside the passenger compartment will define the frequency of standing waves.