DYNAMIC RESPONSE OF A ROTOR INTERACTING WITH A PERIODIC FOUNDATION SUPPORTED BY THE SOIL

Resumo

The dynamic response of mechanical systems depends largely on the boundary conditions prescribed to the system. The dynamic response of a rotor is also strongly influenced by the supporting system. The soil dynamic behavior has a strong influence on the stationary and transient response of a rotor-structure-foundation system. On the other hand, much research has been done on the filtering properties of periodic structures. The current paper discusses a system composed of a rotor, a structure and a periodic foundation supported by the soil. The main idea is to investigate the behavior of this complex system in frequencies where the periodic structure presents a ‘band gap’. The article will address the possibilities of isolating the rotor-structure dynamic behavior from that of soil, in given frequency ranges. The soil is modelled by the Boundary Element Method, the structure is linear and described by the Finite Element Method. The rotor is a Laval-Jefcott rotor presenting internal and external damping mechanisms. The excitations applied to the systems are unbalanced rotor forces or an incoming wave field impinging on the foundation. The questions to be addressed is whether the periodic structure can isolate the rotor system form the soil response for the two mentioned excitation mechanisms.