Enabling Harmonic Balance Methods to be applied for distributed material and geometrical nonlinearities in structural dynamics

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The demand to reduce the impact of aviation on the environment is leading jet engine manufacturers to increase the fuel and propulsion efficiency of its engines. This in turn is pushing materials to its physical limits by undergoing increasingly higher thermo-mechanical loads. In this regime, blades and other engine components are subjected to larger deformations generating nonlinearities which activates new failure mechanisms not dealt before. Therefore, vibration analysis is essential to develop new methodologies for the accurate prediction of components failure. In this project an investigation on the effect of nonlinearities on the dynamic behaviour of the engine blades will be carried out by the Finite Element Method combined with the Harmonic Balance method. This aims to develop and validate methodologies for the identification and control of undesired vibration modes which will inform new design choices. Thus, the objectives of this PhD research are: - To gain a full understanding on the physical phenomenon involved in blade vibrations of the jet engines. - To develop a suitable modelling approach for the blades, including the distributed material and geometrical nonlinearities. - To ensure the nonlinear responses of the structures can be calculated via the Harmonic Balance Method combined with Finite Element model. - To investigate the possible options available to generate reduced order models capturing the effects of distributed nonlinearitiesThe approach to the above goals is to validate the analysis for the nonlinear vibrations and apply the methodology on different type of blades to determine the important parameters for design and the influences of different nonlinearities on the dynamic responses of the blades.