The emergence of production processes such as additive manufacturing made it possible to produce novel structures in terms of topology and composition. It facilitated the realisation of the so-called periodic structures, which had been theoretically studied by physicists and engineers around fifty years ago due to its particular dynamic behaviour, and resurged recently, also under the name of metamaterials.
Periodic structures can be defined as mechanical structures composed of a physically repeating pattern, either due to its geometry, material or supporting conditions, that causes its dynamic behaviour to present band gaps or stop bands; ranges of frequency where the vibration of these structures is forbidden or attenuated. This feature is appealing to many engineering applications, since in the industrial scenario vibrations are often undesirable and some control strategy is necessary to avoid failures. Considering periodicity in the dynamic behaviour of a mechanical part provides a means of having a strategic control of vibrations intrinsic to its design.
Periodicity, dynamic behaviour and design are the key words surrounding this work. These topics will be investigated mainly through experimental methods.
Heat exchangers will be used as the study object and will be explored for their periodicity, as they can be considered an ensemble of nominally identical parts. Its dynamic characterisation is necessary for an understanding of its behaviour and the possibility of improving its design.
Typical failure mechanisms will also be studied as they may reveal dynamic components existent in operation that need to be accounted for when redesigning this device.
With the purpose of understanding both the application and the topics involved in this investigation, methods such as experimental and operational modal analysis are used and combined with wave approach techniques. Together, these methods allow for characterisation of the conventional dynamic properties - also under normal machine operation - and wave parameters that serve as indication of periodic features.
