Research On The Vibration Characteristics Of Marine Floating Raft Vibration Isolation System

The vibration and noise of marine machines affect the safety of ship and the reliability of equipment, and the comfort of people on ship; for warships, the vibration and noise of marine power device influence the marine battle effectiveness and hiding capability, so controlling the vibration and noise in ship is a hotspot of the engineering research all the while.The floating raft system is a novel isolation device for vibration control, which has now started to be widely used for vibration isolation of power plants on ships. The system can depress the mechanical vibratory energy transmission from the power plants to the ship hull; reduce the self-noise and radiation noise of the ship structures, meanwhile, effectively isolate the sudden shocks from the bottom of ship. The theoretical and experimental study on floating raft systems has drawn much attention in recent years.First of all, based on the review of investigative progress, the significance of the thesis is presented and introduced the basic theory of vibration,finite element and the FEM soft ANSYS afterwards. And then, A mathematic model of floating raft system and a finite element model of 4135G marine diesel engine power generator set are set up, the disturbing forces of the set are also analyzed. The influence of different layout and numbers of vibration isolators on the modal and the effect of vibration isolation are studied and analysis shows that the ability of avoiding resonance is better when the isolators'number is six under every diesel engine generator. The influence of different structure of the floating raft on the modal and modal shapes is also studied in chapter four. Changes in cut-out,thickness and area of cut-out are all have great influence on the modal and modal shapes of floating raft.The last part of the paper is the experiment. The experiment of vibration transmissibility characteristics of floating raft vibration isolation system is done by use of the desk of floating raft vibration isolation device which is built by myself,the LMS Test. Lab and the electromagnetic vibration desk. Results show that the ability of shock isolation of floating raft vibration isolation system is better than the ability of vibration isolation. Because the dynamic characteristics of the base affects the impact response, or that the non-rigid characteristic of the base changes the impact isolation characteristic of the device when it makes the high-frequency vibration isolation performance worse at the same time.