Research On Effective Mobility Power Flow Method For Vibration And Noise Control Of Assembled Structures With Cylindrical Shell

Research of the vibration and radiation properties of assembled structures with cylindrical shells have been increasingly become an advanced subject, both for the widely application of rotative structures in the engineering systems, especially the cylindrical shells of the aircrafts, and the complex motion characteristics of cylinders. Predicting the vibration and noise of assembled structures with cylindrical shells is key point to realize low-noise design of structures and cylindrical shells of aircrafts.Energy is a vital parameter in study of vibration and noise of structures. The rule of energy transmission can be studied by the conception of power flow. Mobility, regarded as power transfer function, may be used to summarize the rule of energy transmission. This dissertation is devoted to the study of vibration and radiation of combined structures with cylindrical shells. The main contributions are as follows:1. Three problems emerged from traditional study of mobilities are pointed out. The conception of effective point mobility is described briefly and clearly. By use of effective point mobility, the demerits of traditional study of mobility can be made up, and effective point mobility makes the investigation of the vibration and radiation of structures under complicated excitation possible, which exists in real world widely.2. Effective Mobility Power Flow Method is presented, which is a new theory and is applicable in research of the power transfer principle of complex connected systems with complicated excitation. And then the general equation of effective mobility is acquired.3. Problems for one-dimension exciting are investigated. For an infinite plate with line excitation, the conception of effective line mobility is defined, and academic formulae are obtained. And then, the simulation results of academic formulae are compared with those evaluated by numerical formulae, which results have advantages and disadvantages of their own. At last, line transfer mobility is studied.4. Problem for two-dimension exciting are investigated. In view of the situation in infinite plate with rectangular excitation, surface mobility is defined. Simulation analysis is carried out with regard to the power transfer rule of the points in rectangular surface and of the rectangular surface. Infection of parameters to surface mobility is examined and academic formulae of surface mobility are compared with those evaluated by numerical formulae.5. By using of effective mobility power flow method, vibration level and radiated power level of a element cylindrical shell are studied. Vibration response distributions of single ring stiffened cylindrical shell and multi-ring stiffened cylindrical shell are studied. The simulation results calculations of vibration level and radiated power level are gotten, about the single-ring stiffened cylindrical shell with average distribution force exciting along its one end.6. Power transfer rule of plate coupled with cylindrical shell system and cylindrical shell coupled with cylindrical shell system is studied. Furthermore, power transfer rule of multi-structures series system is educed. Calculation formulae of input power and output power of sub-structures are obtained. By the advantage of effective mobility power flow method, power transfer rules are understandable not only of every structure, but also between the joint structures.