Research on Vibration Isolation Calculation and Design of Ships Based on Spectra Data and FEM

Objectives To conduct the evaluation and optimization of floating raft vibration isolation effects, Methods This paper presents a prediction method for ship vibration isolation devices based on isolator spectrum data coupled with finite element method (FEM). Aiming at the difficulty in accurate dynamic modeling of rubber isolators, this method makes full use of the static stiffness, dynamic stiffness, damping ratio and measured impedance data provided in the Series Spectrum of Vibration Isolators. In FEM modeling, vibration isolators are simplified as spring-dashpot elements, and three schemes for selecting stiffness and damping parameters are compared and analyzed, including static stiffness, spectrum-specified dynamic stiffness, and dynamic stiffness converted from measured impedance. A typical floating raft isolation system is modeled and calculated in Abaqus to verify the parameter sensitivity and calculation accuracy. ResultsThe results show that the dynamic stiffness converted from the measured origin impedance (Z11) is more suitable for vibration isolation calculation. ConclusionsThe proposed method is applied to single-layer and double-layer vibration isolation systems, and the numerical results are in good agreement with experimental data within 400 Hz. Furthermore, combined with the spectrum, rapid evaluation and model selection of five types of rubber isolators are completed. This method can realize vibration isolation prediction and optimization for single-layer and double-layer isolation devices in the design stage, avoid resonance between the natural frequency of the isolation system and the excitation frequency, improve the vibration isolation effect, and meet the acoustic design requirements of ship mechanical systems.