Design Methods For Seismic Restraints In Piplines And Auxetic Broadside Defensive Structure For Naval Ships

Naval ships are important weapons in safeguarding the national marine powersand security. To improve the combat capability and vitality of naval ships relates toboth inside and outside factors.The layout of sesmic restraints in piplines cansignificantly affect the transmission process of dynamic response and noise caused byinternal power equipment. In addtion,broadside defensive structure plays an importantrole in the vitality maintenance of the naval vessels, by effectively reducing thedamage caused by external missile attacks.In this paper, design methods for optimallayout of seismic restraints in piplines and novel auxetic broadside defensive structureare studied, in order to improve stealth performance and vitality of warships.Firstly, considering strength, stiffness, buckling, eigen frequency and vibrationlevel difference constraints, three kinds of comprehensive seismic restraints allocationoptimization design methods are proposed:1) the code-based design method;2) thegeometry optimization-based design method;3) the topology optimization-baseddesign method. According to the presented methods, the initial numbers of seismicrestraints can be defined by ASME B31Code in code-based method, or by randomassumptions in geometry optimization-based method. Then the locations of eachrestraint are obtained by geometry optimization. An iterative procedure was employedin solving the presented optimization models, in which an adjustable searching step isadopted to determine the critical distance of the neighboring restraints. The criteria ofthe deletion and adding of the seismic restraints in pipeline depend on the satisfactionof behavior constraints and the value of critical distance. The topology-basedoptimization model for allocations of seismic restraints can be got by introduction ofbased restraints in pipelines. This model is a0-1integer programming problem andsophisticated to solve. By connecting the topology design variables with the geometrydimensions or material elastic modulus, it can be simplified and adapted to moreoptimization algorithms. Engineering design examples showed the effects of differentchoices of the objective functions on the optimal results, like construction costs, themaximum deflection, and the structural strain energy of pipelines. The effectivenessand simplicity of the proposed methods in engineering design are also demonstrated.Secondly, for conventional defensive structure, improvement on capacity ofcounter-impingement relies on high-performance materials and special design onstructure size. In this paper, a novel auxetic defensive structure with negative Poisson’s ratio is proposed in order to achieve better anti-shock performance bydesign of auxetic configuration. The process of an anti-ship missile impinging on andpenetrating broadside structure is simulated by the non-linear finite softwareLS-DYNA. The effects of different parameters on broadside structure, like auxeticconfigurations, materials, sizes and thickness of honeycomb cell, are studied andcompared. Numerical results indicate that counter-impingement capacity can beimproved by adoption of auxetic broadside structure is better than that of positivePoisson’s ratio structure. It can be further improved with applications of propermaterials, sizes and thickness of honeycomb cell.