Design Of Arbitrary Poisson’s Ratio Metamaterial And Its Application In Ship Vibration Reduction

The development trend of large-scale and high-speed ships has caused increasing vibration and noise of equipment on ships.It also causes natural frequency of ships to become lower,which poses greater challenges to ship vibration and noise reduction.Traditional ship vibration and noise reduction measures such as floating floor,double-layer and floating raft vibration isolation systems are difficult to achieve lightweight design and vibration control target.By design of arbitrary Poisson’s ratio and zero Poisson’s ratio metamaterials,this dissertation explores the application of metamaterials in ship structures to achieve both lightweight design and vibration and noise reduction.This dissertation studies the functional element topology optimization method(FETO method)for metamaterial design.The design of metamaterials with specified Poisson’s ratios under different shape topological ground structures is discussed,and a series of metamaterial functional element configurations with specified Poisson’s ratios were designed by optimization.Some topological configurations of the optimal functional elements were evaluated and their mechanical properties were calculated and analyzed.The results show that the holes in the topological ground structure will reduce material consumption and improve stiffness and vibration isolation performance of the metamaterial structure,while making configuration stability worse.Circular topological ground structure uses less material than rectangular topological ground structure in designing metamaterials,and its vibration isolation performance of metamaterial structure are better.Triangular topological ground structure is more likely to obtain the configuration of large Poisson’s ratio functional element.These results provide references for subsequent design of arbitrary Poisson’s ratio metamaterial through FETO method,as well as the application of the designed metamaterial on ships.The optimization model in FETO method when designing zero Poisson’s ratio metamaterials is completed by multiple measuring points in topological ground structure.Two types of topological configuration of zero Poisson’s ratio metamaterial were extracted,which were based on maximum compliance objective and minimum mass objective optimization models.The zero Poisson’s ratio effects of these two configurations was numerically verified.Static and dynamic analysis of zero Poisson’s ratio metamaterial structure shows that zero Poisson’s ratio metamaterial has certain bearing capacity.Compared to minimum mass objective optimization model,the metamaterial structure based on maximum compliance objective possesses better in-plane specific stiffness and vibration isolation performance.There are also large peaks in vibration level difference curves of these structures at some frequencies.The marine ribs and girder of metamaterial structure were designed by selecting negative Poisson’s ratio metamaterial functional element configuration with better load-bearing and vibration isolation performance.Structural vibration and underwater radiation noise of a ship was analyzed after metamaterial ribs or girders was replaced to the corresponding structure under the auxiliary engine room of this ship.The results show that the control effect of ship vibration and noise by using specified Poisson’s ratio metamaterial structure is not obvious.The metamaterial girder can reduce the underwater radiation noise slightly.The number of functional elements arranged in the metamaterial structure has a certain impact on its vibration and noise reduction performance.Under the background of inner shell shape conservation of submarine and other underwater equipment,the zero Poisson’s ratio metamaterial functional element configuration was extracted and arranged as the ring-rib structure of a deep-sea double-layered cylindrical shell.Three types of ring-rib structure in cylindrical shell,metamaterial ring-rib,conventional solid ring-rib and structural topology optimization ring-rib,were calculated and compared in terms of mechanical analysis.The result shows that zero Poisson’s ratio metamaterial has better shape conservation characteristics,which is able to achieve less deformation of the inner shell under the hydrostatic pressure while realizing lightweight design.The vibration and underwater radiation noise properties of metamaterial cylindrical shell and solid ring-rib cylindrical shell were compared and investigated.Studies have shown that zero Poisson’s ratio metamaterial ring-rib is better in terms of vibration isolation performance.It can also reduce the underwater radiation noise of cylindrical shells effectively.The wall thickness of metamaterial is of vital importance to the vibration and noise performance of cylindrical shell.These conclusions show that zero Poisson’s ratio metamaterial has broad application prospects in ships,submarines and other underwater equipment.