Research On Vibration And Shock Isolation Of Double-arrowed Auxetic Structure In A Ship Foundation

Vibration and shock isolation on board plays an important role in making sure of ship’s comfort,invisibility and safety.The foundation servers as the basis for fixing equipment and hull,transferring the dead weight of equipment and the dynamic load generated by some operation to the hull,as well as transferring the shock load to equipment.The foundation plays an important role in the design of ship’s vibration and shock isolation.However,it is difficult to balance the vibration isolation and shock isolation performance of the foundation.In this dissertation,based on the design of conventional foundation,a new type of auxetic arrowed structure is used to replace the face plate and web of conventional foundation.The main work of this paper include:(1)The in-plane elastic modulus,in-plane shear modulus,Poisson’s ratio and relative density of the double-arrowed structure within the linear elastic range are derived by using the girder theory,and the accuracy of the theoretical derivation is verified by the tensile test.The experimental results show that the theoretical formula has good accuracy in the small elastic deformation range.(2)On the basis of the mechanical parameters of the double-arrowed structure,three equivalent theories(sandwich plate theory,Reissner’s equivalent stiffness theory and Hoff’s equivalent stiffness theory)are respectively applied to the double-arrowed honeycomb plate.By establishing the standard model,the accuracy of three kinds of equivalent theories are compared in dynamic responses,such as:displacement,stress and modal frequency.It is found that the sandwich plate theory has the highest equivalent accuracy and is more suitable for the equivalent of the model in dynamic analysis.(3)Based on the sandwich plate theory,the finite element model of foundation was established,and the static characteristics,modal characteristics,vibration and shock isolation performance of the foundation were analyzed.And the results were compared with the conventional foundation.The result shows that the maximum stress decreases by 24.5% and the maximum vertical displacement by 4.4% under the static load,the vibration level drop increases by 90.6% under the action of simple harmonic excitation force,and the impact amplification coefficient decreases by 59.8%under the shock load.The new type of auxetic arrowed structure has better static and dynamic performance than conventional foundation.(4)The influences of structural parameters on the isolation performances of vibration and shock are discussed.And the natural frequency of the base,the impact amplification factor,the vibration stage drop and the maximum impact stress varying with the structural parameters on are obtained.Finally,under the constraints of the vibration stage drop and the shock amplification coefficient,synthetic dynamics optimization design of the foundation is carried out.Optimization results indicate that by applying the auxetic double-arrowed structure and synthetic dynamics optimization design,performances both in vibration reduction and shock isolation can be improved.