Vibration Test And Analysis Of The Yacht

This paper takes a certain type of FRP yacht as the research object,firstly,the honeycomb sandwich plate is investigated by using vibration measurement and FEM method in vibration performance,which is prepared for the further analysis of the hull.The inherent vibration characteristics of the honeycomb sandwich plate are acquired by LMS Test.lab modal analysis for the honeycomb sandwich plate.The establishment of the equivalent FEM model of the honeycomb sandwich plate is based on the test results.The model parameters is adjusted in ANSYS to make the vibration characteristic of the equivalent FEM model close to the modal test results.Comparing the FEM model with the test result,it is found that they are similar in the first three order modes,and the relative error of inherent frequency is within the reasonable range.The FEM model can reflect the real vibration characteristics of the honeycomb sandwich plate.In this model,the honeycomb layer is equivalent to an isotropic plate with constant volume and the same thickness.To obtain the inherent vibration characteristics of the hull,the hull dry and wet modal tests are carried out in the plant and the wharf.The dynamic performance of the hull is analyzed in the frequency range of 0-50 Hz.It is found that the lower order dry modes are swing,twisting and bending of the hull,accompanying with the partial movement.Affected by attached water,tides and the weight distribution of the testers and equipment,the lower order wet modal are swing,contraction,torsion of the hull.Comparing the dry with wet modal results,it is indicated that the inherent frequency of the vertical and the horizontal first order bending modes show little deference,which verifies the reliability of the modal test.The establishment of the hull FEM model is based on the equivalent FEM model of the honeycomb sandwich plate and the layer scheme of the hull laminated plate.The simulation analysis is carried out based on the dry modal test,it is shown that three order modes are similar in the low frequency range,and the relative deviation of the inherent frequency is small,which verifies the accuracy of the established hull FEM model,and also the reliability of the modal test.This hull FEM model can be used for the further research of the dynamic characteristics of the FRP yacht,and also provides a theoretical basis for optimization design of the hull structure.According to the FEM analysis and the modal results,it is found that the structure stiffness of the FRP yacht shipboard is relatively insufficient.If the hull is under a state of low frequency for a long time,it would cause fatigue damage.Therefore,the structure stiffness of the hull shipboard should be paid more attention on the hull structure optimization design.In this paper,a preliminary research on the dynamic characteristics of the yacht is carried out,which may provide a certain reference and guidance for the optimization design of yacht structure and the research of yacht comfort.