Structural Dynamic Optimization And Redesign For The Cruise's Propelling Machinery Room

The cruises are usually equipped with pod propulsion duo to the harsh demands of maneuverability,reducing noise and vibration.The propelling machinery room is the most vibrating area because of the exciting force produced by the propeller while in the cruising state.The exciting force of pod propulsion can be calculated.Then the structural vibration will be reduced and vibration transmission characteristic will be improved with the optimization of propelling machinery room structure.Currently engineers generally separate the structural natural frequency with the excitation frequency to avoid resonance and noise.And the structural dynamic optimization usually depends on experience.So this article investigates the coupling vibration of the cruise main body and pod propulsion firstly.The vibration transmission characteristic research is conducted through 3 methods afterward.And finally reducing the structural vibration with topology optimization and redesigning the propelling machinery room.The main research work are as follows:(1)Building 4 different kinds of FEM model which are in different scales according to structure drawing and layout drawing.Then calculating the natural frequency of different FEM models and estimating the coupling vibration between cruise body and pod propulsion.The selection of best vibration calculating FEM model will be finished at last.(2)With the selected vibration calculation FEM model,the vibration response calculation could be finished using Nastran and Optistruct.On this basis,this article carries out the vibration transmission characteristic research of propelling machinery room according to direct contrast method,transfer function method and vibration power flow method.(3)Based on the vibration transmission characteristic research,three structural dynamics topology optimization models are built.The optimization variables are the material's density based on the SIMP material density model.Setting the vertical velocity response as constraint and defining the volume function as the objective function.This article explores the interpolating function and different design area's influence on the optimization result.Redesigning the propelling machinery room structure according to the optimization result and inspecting the design scheme with vibration response calculation and increased mass.The structural dynamic optimization and redesign for the cruise's propelling machinery room will be finished after multiple iterations of redesigning and calculation.