Mobility Power Flow Research On Structural Sound And Vibration Analysis

The research was sponsored by Foundation of National Natural Science and Northwestern Polytechnical University Graduate Pioneering Seeded Foundation.Mobility power flow (MPF) method combines the concepts of mobility and power flow, it can reflect the vibration energy distribution inside of the structure directly, and can give the vibration energy and power flow transmission properties among substructures indirectly. However there still has a long way to the widely MPF method application, and a great deal of calculation works is needed. This thesis was completed in order to solve the key techniques in the process of structure sound & vibration investigation.Elastic and beam-stiffened cylindrical shells are common structures that applied in ship structures, torpedoes, as well as aviation and architecture establishments, it has great significance to study the vibration energy distribution and transmission properties for the future sound & vibration research of complex structures. By applying the MPF method, all the vibration characteristics of the cylindrical shell under external excitations were achieved in the thesis.Research of the structure sound & vibration is incomplete if there is no investigation about structure sound radiation. Because compared with structure vibration distribution and transmission, sound energy that radiated to the surround space also is a problem that can not be neglect in virtual project. Sound radiation of plate and shell structures in air medium was studied in this thesis, and the mobility-form expressed sound radiation efficiency was obtained. Compared with the classical calculation formulas, the reformed ones can improve the predicting precision greatly at frequencies near the critical frequency.To solve the complex coupled structure's vibration characteristic is the motivity and object to develop the MPF method. In this thesis, attempts were done in applying the MPF method to solve complex coupled structure's vibration characteristics. One attempt was for the coupled cylindrical shell which consists of two semi-infinite cylindrical shells, the other attempt was for the L-shape plate which is assembled by two thin plates perpendicularly. Coupling effect between the two substructures and the vibration response of each substructure were received under external point harmonic force excitations. All the conclusions are useful and have conducting significance for...