Topological Optimization Of Thin-walled Stiffened Structure Considering Local Shape Preserving Constraint

Thin-walled stiffened structure has the characteristics of light weight,high specific stiffness and specific strength,good spatiality and flexibility in shape,which is widely used in aerospace,automobile,ship and other structures.Its reinforcement layout may affect the structure performance.Therefore,it is necessary to study and establish a reasonable design method for stiffener layout of thin-walled structure.The topological optimization method has a strong ability of structural configuration design and can be used in the design of stiffener layout of thin-walled structures.Due to the special function and performance requirements,thinwalled structure has shape preserving requirements for local structure,i.e.the shape of local structure is required to be maintained.For example,the fuselage structure requires the window to maintain a fixed shape during the working process.Thus,the constraint of local shape preserving must be considered in the reinforcement layout design of thin-walled structure.In this paper,the problem of stiffener layout design for thin-walled structures with shape preserving constraints is studied.The constraint model which can reflect the shape preserving feature and a topological optimization method for the layout design of thin-walled structure with shape preserving constraint are both established.The specific research results are as follows:(1)Optimization design method of reinforcement layout for thin-walled stiffened structure: The stiffener is modeled by solid element in traditional optimization of thin-walled stiffened structure.Huge degrees of freedom will cause great time consumption and even hinder the optimization process for the large scale of structure.Therefore,we need to find a more efficient way.In this paper,OptiStrut is used to optimize the design of thin-walled stiffeners under different modeling methods and the geometric models of results are rebuilt.After that,the static and dynamic performance simulation of the new structures is carried out.(2)Structural topology optimization design method considering local shape preserving constraint:In order to control the local warping of structure to a certain extent,shape preserving design of structure is studied.By introducing the concept of surface shape variance,the level of local warping deformation can be described in this research,and a new mathematical expression of shape preserving constraint is established.Then the mathematical model of conformal optimization and the sensitivity analysis are completed based on the SIMP method.And by using the moving asymptote method(MMA),the Matlab program of solving this kind of problems is completed.After that,the design for different of load and shape preserving domain are discussed in detail.Besides,the advantages of this method can be found by comparison with the result of the traditional topology optimization method.(3)Topological optimization of thin-walled stiffened structure considering local shape preserving constraint: Based on the research contents(1)and(2),the mathematical expression and solution strategy of thin-walled stiffened structure considering local shape preserving constraint are established.A typical thin-walled stiffened structure,the fuselage of aircraft with the demand of restraining local warpage is designed here,by comparing the deformation of shape preserving domain before and after applying the surface shape variance constraint,the validity of the method is verified,and the application potential of this study in the actual engineering design is also demonstrated.