Research On Methodology Of Optimization Design For Composite Material Pressure Hull Of Underwater Vehicle

As an indispensable technical equipment for the development of marine resources,underwater vehicles have been the focus of development in the global marine equipment field because of their unique advantages.As a key component of an underwater vehicle,the pressure hull provides safe watertight space for major equipment and overall buoyancy reserve.Therefore,it is of great significance to optimize the structure and weight of the pressure hull.With the development of ocean exploration,the working depth of the underwater vehicles is increased,and the structural performance requirements of the pressure hull are getting higher and higher.As novel materials,the composite materials have many advantages such as high specific strength,high specific stiffness,corrosion resistance,electrical insulation and designability.The underwater vehicle pressure hulls made of composite materials have obvious advantages over the ones made of metal.At present,the construction of underwater vehicle equipment structures using composite materials is mostly in the experimental stage,and mature design methods and construction specifications are still in demand.In this paper,the underwater vehicle composite pressure hull is taken as the research objective,where a series of researches are carried out on the influencing factors of the structural properties of three kinds of pressure hulls,namely an unstiffened pressure hull,an evenly ring stiffened pressure hull and an unevenly ring stiffened pressure hull,the deterministic collaborative optimization of the pressure hull and nondeterministic collaborative optimization considering the reliability.This work provides the basic reference for practical application of the composite pressure hulls.The main contents include:By analyzing the characteristics of the composite material components,the carbon fiber/epoxy resin is selected for the material of pressure hull of underwater vehicle.To solve the problem of structural mechanical performance analysis of composites,the elastic mechanics analysis methods and composite failure criteria are studied.The finite element analysis methods for composite pressure hull failure and buckling are verified by test results.Based on the method of design of experiment the accuracy of elliptic basis function(EBF)neural network approximation model is studied.Comparison on applicability and accuracy of EBF approximation models and other common models have been made by applying function examples with the focus on function dimensions,nonlinearity level and sample quantity.And the engineering feasibility of EBF neural network approximation model are studied by using it to predict the structural performances of composite material pressure hull.The EBF network approximation model is chosen to replace the finite element simulation to participate in the analysis and optimization design for the composite pressure hull of the underwater vehicle.According to the optimal Latin hypercube method of design of experiment,the approximation model of composite pressure hull is established using finite element analysis samples based on EBF network to replace large-scale structural calculations.Based on the method of meso and macro mechanics analysis of composite materials,the effects of fiber,matrix properties and ply angles of laminates on the structural performance of unstiffened composite pressure hull,evenly stiffened composite pressure hull and unevenly stiffened pressure hull are studied.According to the designability of the composite materials,the lamination parameters are introduced as the coordination variables.With the target for minimum pressure hull weight,the optimization design framework of collaborative optimization is established including the layout and layup optimization subsystems.Combined with the EBF approximation model technique,the hybrid optimization method is applied to conduct the integrated material and structure collaborative optimization for the composite pressure hull of underwater vehicle.It solves the difficulty and low efficiency problem of direct optimization,and can also be extensive applied to the overall design of carrier structure of composite underwater vehicle.Considering the influences of the designability and the uncontrollability of the processing on the structural properties of the composite material pressure hull,the reliability analysis is carried out for the deterministic optimization scheme of the composite pressure hull structure based on Monte-Carlo sampling.Aiming at solving the random failure problem of underwater vehicle composite material structure,on the basis of deterministic collaborative optimization,using 6 sigma design theory,a nondeterministic collaborative optimization framework for composite material pressure hull is proposed considering reliability with the Monte-Carlo reliability analysis embedded in optimization,where the sigma level is the metric of reliability.The presented optimization strategy can solve the structure failure problem caused by parameter stochastic volatility and obtain the optimal scheme considering quality and robustness comprehensively.