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

减少航空对环境的影响的需求导致喷气发动机制造商提高其发动机的燃料和推进效率。这反过来又通过承受越来越高的热机械载荷将材料推向其物理极限。在这种情况下，叶片和其他发动机部件受到较大的变形，产生非线性，激活新的故障机制没有处理过。因此，振动分析是必不可少的，以开发新的方法，准确预测的组件故障。在本项目中，将采用有限元法与谐波平衡法相结合的方法，对非线性对发动机叶片动态特性的影响进行研究。其目的是开发和验证识别和控制不期望的振动模式的方法，这将为新的设计选择提供信息。因此，本博士研究的目标是：-获得对喷气发动机叶片振动所涉及的物理现象的全面了解。- 为叶片开发合适的建模方法，包括分布式材料和几何非线性。- 为了保证结构的非线性响应可以通过谐波平衡法与有限元模型相结合进行计算。- 为了研究可能的选择，以产生降低的阶模型捕捉的影响，分布非线性的上述目标的方法是验证的非线性振动的分析和应用的方法，在不同类型的叶片，以确定设计的重要参数和不同的非线性对叶片的动态响应的影响。

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.