Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Numerical Simulation of Vibration Isolating System Based on Parameter Identification of Mechanical
Impedance
Haixiong Zhu, Yun Wang, Jianwei Wu*, Weihua Shi, Chao Shang
Wuhan Second Ship Design and Research InstituteWuhan, Hubei, China

widely used. The floating raft was investigated (Shen and Yan,1994)
and the operation results showed that the vibration isolating effect of
the floating rafts could be higher than 35dB at frequency period of
10Hz to 8kHz.
The vibration isolation design process of the machinery could bedescribed as follow. Firstly, the preliminary scheme is designed
according to the mass distribution, the operating parameters and theoverall dimension of the machinery. Secondly, the vibration modalfrequencies, the impact resistance and the isolation effect are calculatedand verified. After that, the vibration isolating scheme is modified
according to the calculation results and the designed scheme is finalized.
The vibration isolating effect of the system is the most important indexof the design. The calculation verification should be conducted in highaccuracy and efficiency. The design and analysis methods areinvestigated extensively at present (Liu, 2016; Huang, 2017). The mostwidely used methods include the rigid multi-body dynamic analysis
method, the four-pole parameter matrix method (Gardonio and Brennan,2002), the impedance synthesis method (Zhu and Zhang, 2001) and thefinite element method (Liu, Cao, Lü and Yang, 2018).
The rigid multi-body dynamic analysis method, the four-pole parameter
matrix method and the impedance synthesis method are focused on thetheoretical calculation. The calculation accuracy could not fit thedemand of engineering application. The finite element method is moreaccurate, but the calculation efficiency depends on the fineness of themodel. In view of engineering application, the FEM model was usuallysimplified. The rubber isolators, key components of the vibration
isolating system, were usually simplified to linear springs in single
direction (Zhou, Wang, and Sun, 2006). The dynamic mechanicalcharacteristics of the rubber isolators were not considered. To improvethe calculation accuracy, the dynamic characteristics of the rubber
isolators could be represented by the mechanical impedance. The
numerical experimentation has been conducted (Ji, Lu, Wang andCheng, 2013) and the results were demonstrated.
This paper focused on improving the simulation accuracy andefficiency of the vibration isolating effect. The research model includes
the operating machinery, rubber isolators distributed in two layers, thefloating raft, and the base structure, as shown in Fig. 1. The operatingmachinery in this paper is plunger pump with motor.

ABSTRACTIn field of ship and submarine, operating machinery are usually
installed on flexible foundation, considering vibration isolation andimpact resistance. The vibration isolating system, composed of floating
raft and rubber vibration isolators, should be parametric designed toensure the vibration isolating effect. At present, the methods ofanalytical calculation and simplified simulation were widely usedduring design process. The rubber vibration isolators, key componentsof the vibration isolating system, were mostly equivalent to linear
springs with constant stiffness in past research. The dynamic
mechanical characteristics of the rubber isolators were not considered.
In this paper, a new numerical simulation method based on parameter
identification of mechanical impedance was investigated. The
mechanical impedance of rubber isolator in vertical, transversal andlongitudinal directions were all considered. The frequency dependent
mechanical parameters were identified from experimental curves. Then,the equivalent FEM model of the vibration isolating system was built
layer-by-layer. Results suggested that the impedance of each layer
could be simulated with high accuracy. On this basis, the global modelof vibration isolating system of the operating machinery was built andthe vibration isolating effect was calculated. Compared to theexperimental analysis, the error of the simulated result was within 3dB(10Hz-500Hz) and satisfied the demand of engineering application.

KEY WORDS: Numerical simulation; vibration isolating system;mechanical impedance; parameter identification.

INTRODUCTION
In field of ship and submarine, vibration energy of the operatingmachinery mainly transfers through the bearing foundation. The
vibration energy excites the hull structure and results to acoustic
radiation. To control the sound and vibration of the marine vehicles, theenergy transfer of the operating machinery should be reduced by designof flexible installation. At present, the vibration isolating techniquesuch as the floating raft or double-staged vibration isolating devices are3952