The Research For Vibration Of The Stern Structure

As one of the important references for the ship's design,the vibration has influence on the normal work of ship equipment and the crews.Studyingthe natural frequency and vibration responseof the stern is worthwhile for the ship structure design in actual engineering.Under the guidance of vibration theory,the article completes a series of analysis of the stern with conventional propeller,including natural frequency,vibration test,vibration response and control measures based on structure design.The stern vibration mainly includes calculating bottom grillage natural frequency,researching the influence of curvature to the added massand analyzing the cabin vibration.The research on the bottom grillage shows that the FEM model should be extended to the platform structure.Outboard the added mass is simulated by the virtual mass method.By studying the influence of the curvature to the bottom grillage on the added mass,in the same mode,the effect of curvature on the added mass is about 15% compared with the result of the formula.When it comes to the natural frequency of stern cabin,the FEM mixed model has been proved that the results are similar to the model of six different proportions.Only the cabin modelbeing used,the FEM model should be extended to the vibration node which was the first-order vertical vibration of hull girder.Compared with stern vibration test,it shows that the result of FEM is similar toexperimental test.Therefore,itis almost correct that the FEM can be used to calculate the natural frequency of the stern.And the virtual mass method could accurately simulate the influence of the outboard water to the vibration of stern.The vibration response of the stern is figured out with using the mode superposition method.And the result is checked under the vibration evaluation standard.The control variable method is used to research influence of structure designed parameter to the stern vibration.It shows that tanks,ribs and longitudinalcould improve the vibration response of the bottom grillage.The pillars haves a good effect on the vibration control of deck.Damping and longitudinal bulkhead could effectively reduce the sternvibration response.The combined scheme could be better used to control vibration.It is of valuable reference to stern structure design and vibration control.