The Study Of Analyze Methods For Vibration Transfer Behaviour Of Complex Mechanism Structures

Mechanism noise is the main acoustic source of cruising submarine. The workingmachines product vibration. Through structures inside, the vibration energy is transferred toshell of submarine. Then the underwater acoustic waves radiate from shell into water. Thevibration energy, which arriving the shell, will be reduced efficiently if vibration isolationequipments are installed. And the mechanism noise will be reduced when submarine cruising.After a set of vibration isolation equipment is installed, we have to face practical problems,such as whether the performance of this equipment fulfills demands of the design, and how tofind out the source places or transfer paths when there is vibration energy leaking. Studyingvibration transfer behaviors of structures is one method to solve these problems, and is apractically way to predict mechanism noise of submarines.In this paper, the theory models of vibration isolation systems are built，which are usuallycomplex mechanism structures, and the models transfer behaviors of vibration power flow isanalyzed. The estimating method of transfer behaviors for vibration in structures is studiedalso. The evaluating method of vibration in structures is given, only with measured responseof vibration. By analyzing the model simulation signal and experiment signal, the estimatingmethod of vibration transfer behaviors for structures is validated.The theory models of simplified vibration isolation systems are built by substructuremobility method, including single floor vibration isolation system model and double floorsvibration isolation system model. The vibration transfer behaviors of isolation models aregiven by analyzing power flow of some nodes in the model systems. At the same time, theinfluence of transfer behaviors of power flow by varying structure parameters is discussed. Itshows that, it will reduce the peaks number of power flow spectrum which transferred to thebase, if the isolators nearest to the base are set symmetrically. And it will reduce the powerflow, if the stiffness of isolators is properly decreased or flexibility of base is properlyincreased.The ratio function method is proposed to estimate the behaviors of vibration transfer,which is mainly used when the signals of vibration response are only measured. The ratiofunction method is discussed separately for the situations of single-driving-source andmulti-diving-sources. The degree, that estimating veracity is influenced by measurement noise,is also discussed. The curve fitting results for ratio functions are given, using method oforthogonal polynomial fitting. With simulation signal and theory models, vibration transfer behaviors of models are analyzed, as getting the analyzing results of frequency responsefunction and ratio function. With ratio function method and simulation data, the estimatedvibration transfer behaviors of models are given. The responses of vibrating structures arepredicted by the estimated results of vibration transfer behaviors. Then the ratio functionmethod is validated.The experimental study of vibration transfer behaviors is carried on a bay section withsome vibration isolation systems. With driving sources working, the data of vibrationresponse on different points is measured. The responses of vibrating structures are predictedwith the estimated results of vibration transfer characters, which are estimated by ratiofunction method. This method is validated by uniformity between the results of predicted andmeasured.