The Method For Topology Optimization Of Coupling Structure Of Frames And Shell

Shell structure and rigid frame are widely used in engineering for many advantages of light weight,low cost and simple construction.In order to adapt to the development of modern shooting range measurement technology,large-sized optical structures,such as large-sized optoelectric theodolites,where welded rigid frame and shell can be used as an important component of the supporting system.In this paper,topology optimization design of the coupling structure between rigid frame and shell is based on the main supporting structure of hollow steel pipe welded into thin steel shell.The lightweight design scheme of turntable which is an important part of the supporting system is determined according to optimization results.And the dissertation mainly includes the following contexts:Based on the discrete ground structure method and the continuum density method,the unified SIMP method is proposed to implement both the topology optimization of rigid frame and shell.The 3D Euler Beam element and the 3D Ressner-Mindlin shell element are used to simulate the rigid frame an the shell structure respectively.The joints between them are simulated by constraining the degree of freedom of the points which are at the same location of two structures.Ground structure in non-convex design domains is generated based on random geometry and mesh by the ground structure connectivity level for the complex and arbitrary shape.This method only needs building model once.It uses directly the boundary as the criteria for collision detection which simplifies the process.Ground structure in one level or in full connection is generated based on arbitrary mesh type in any design area.Topology optimization method for the rigid frame and the shell structure is based on the SIMP method.Firstly,design domain of the rigid frame structure optimization problem described by ground structure.Secondly,optimization problem of the minimum strain energy under stress constraints is solved by continuum topology optimization and obtain the optimal topology of the rigid frame structure.Thirdly the short bars are avoided in the results by controlling the number of nodes to simplify the manufacture.Lastly,the optimal topology of the shell structure is obtained by solving the optimization problem of the minimum strain energy under stress constraints with SIMP method.For topology optimization method for the coupling structure between rigid frame and shell: the design area of the rigid frame and shell is connected by constrained points.Firstly,the optimal rigid frame structure is obtained by solving the optimization problem of the minimum strain energy under the stress constraint with SIMP method based on the coupling structure.Secondly,topology optimization results of the rigid frame structure is converted into specific design and the shell structure is added to the designed rigid frame.the optimal shell structure is obtained by solving the optimization problem of the minimum strain energy under the stress constraint with SIMP method based on the new coupling structure.lastly,the topology optimization of the rigid body and the shell structure in coupling structure between the rigid frame and shell can be obtained respectively.Optimize the turntable of the main supporting structure of a 1 meter aperture theodolite by the topology optimization method mentioned above.According to the results based on multi-load topology optimization,the design scheme of turntable is determined.The finite element analysis of the results illustrate that the weight is reduced significantly while meeting the requirement of stiffness and eigenfrequency.