A FE-SEA Hybrid Method For Vibration Analysis Of Complex Structure

Nowadays, it is important to study vibration of complex structures for controling noise and vibration. In this thesis, a FE-SEA hybrid method is proposed based on finite element method (FEM) and statistical energy analysis (SEA), which can be applied to vibration analysis of complex structures in a broadband frequency range.Firstly, the basic principle and steps involved in FEM and SEA are examined. Meanwhile, SEA approach is applied to solve vibration response of an aircraft cabin. Then a SEA-based model of the structure is established, and the SEA parameters are obtained by theorical and experimental method. At last, the sound power calculated by AutoSEA2 software in the cabin is good agreement with that given by experiments.Secondly, due to the drawback of FEM and SEA, which can be respectively used in low and high frequency region, a FE-SEA hybrid method is given by combining FEM with SEA method. For the FE-SEA hybrid method, the modal superposition approach is used to express the vibration response while the system degrees of freedom are partitioned into a "global" set and a "local" set. The global equations of motion are formulated and solved by FEM while the local equations of motion are given and then solved by using SEA method. It is proved that the influence of the local modes on the global modes is originated from damping, whereas the influence of the global modes on the local modes is due to the input power.Lastly, the longitudinal and bending waves' behavior are respectively predicted by the proposed FE-SEA hybrid method for two coupled one-dimensional rod. And the relative parameters, such as the modified dynamic stiffness matrix AD, the modified forcing vector AF and power input from the global modes P~g, are deduced. It is shown from computer simulations that good results can be obtained from low to high frequency excitation.