Study On Transmission Characteristics And Vibration Evaluation Of Vibration Isolation System

With the developing of the Green Shipping Technology, the vibration control of marineequipments has been drawing more and more attention. It is a focus problem that how toevaluate the vibration of marine equipments, which has the characteristic of heavy weight andlarge volume, because when vibration is tested onshore, the base impedance of the bench andthat on ships are quite difference. There are mainly two contents in this problem, one is whichparameters could be used to evaluate the vibration of marine equipments not only accuratelybut also easy to realize in engineering; the other is how to obtain the vibration state ofoperating equipments from onshore testing data.The research in this thesis is carried out on the first content. Firstly, how input powerflow and transfer power flow of single-stage vibration isolation system and two-stagevibration isolation system changed with parameters of the base and vibration isolator wasderived. Combined with the calculation of vibration acceleration and transfer force of sidehanging equipments, different vibration evaluation indexes of vibration isolation system werecompared and the application scopes of them is studied. The results showed that accelerationlevel could be used to evaluate vibration of equipments in high frequency, for it was barelyinfluenced by parameters under elastic mounting condition in this interval. And in lowfrequency the transfer force could be used to evaluate vibration of equipments, the value of itis easy to obtain for it is only related to the stiffness of vibration isolators in this interval.Then the two-stage vibration isolation test bench of flexible foundation was designed. Theaccuracy and practical of pre-pressing piezoelectric force transducer was verified by the strainforce transducer, a two-sensor testing method was put forward. And the force which transfersto foundation through vibration isolator in Single-layer Vibration-isolating System wasestimated using four-end parameter analysis method and least square method. Comparingwith the testing data, the accuracy of results obtained by the two methods was analyzed andthe error causes were discussed. At last, the vibration power flow was tested and calculated,the transfer law of vibration power flow and how it changed with stiffness and damping offoundation is studied. After finished above-mentioned work, the vibration estimating systemof elastic mounting equipments was preliminary established.The calculation and testing results show that varying of foundation parameters just has influence on power flow input to foundation; it has little influence on power flow of the wholesystem. Power flow input to foundation would reduce if stiffness of arbitrary vibrationisolator reduced or mass of arbitrary subject added. The increasing of damping causes inputdamping reduced at nature frequencies of structure, and increasing at other frequency ranges.For the side hanging equipments, the examination method that just testing vibrationacceleration level perpendicular to installation plane is imperfect for the force and vibrationacceleration level transfer to foundation in the other two directions could possibly be moreserious than that in vertical direction under this installation state. The accuracy of thetwo-sensor testing method is much higher than the traditional method in low frequency. Theaccuracy and anti-noise property of four-end parameter analysis method are better than that ofleast square method when estimate the transfer force. In low frequency the result error usingfour-end parameter analysis method was just about1dB, which satisfied the requirements ofengineering application. The force obtained is feasible to be a vibration evaluation index. Theanalysis result shows that the testing and estimating accuracy and anti-noise property oftransfer force are better than that of vibration power flow; the transfer force is more suitableto be a vibration evaluation index.