The Optimization Of Thin Thermal Plate And Shell Structures Considering Temperature Correction

Thin shell structures are widely used in aerospace,transportation,machinery and other engineering fields.Such structures are usually subjected to thermal load or thermal load.The structure under the condition of temperature load is called thermal structure.Thermal expansion occurs when the thermal structure is restrained,resulting in thermal deformation and thermal stress of the structure.When the stress increases to a certain value,the overall performance of the structure will be reduced,and the structure will become invalid and unable to be used in severe cases.The analysis and design of thermal structure,as far as possible to reduce the thermal deformation and thermal stress of the structure,has always been one of the research topics in the field of structural optimization design.In this thesis studies the optimal design of elastic thin plate shell structure under temperature field.Based on Ni Xiaoqin et al.^[1-2]to study the elastic thin plate shell under the uniform temperature field,this paper adopts the same method to construct the optimization formula of the thin plate.Given the volume of sheet material and the expression of the strain energy expressed by the stress under the temperature load is adopted,and the extended method including the temperature term is constructed by the criterion method,and the optimal thickness distribution diagram of the thin plate shell structure under the action of the temperature field was deduced.Compared with the classical thickness distribution optimization formula,the temperature correction term was added in the study,and a more complete optimized thickness profile of the variable thickness distribution was given.The optimization algorithm was implemented with the secondary development function of ANSYS software and MATLAB.In the first part of this thesis,the structure of elastic thin plate is studied.With the material volume as the constraint,the overall structure strain energy is minimized as the objective function,and the optimization formula of the thickness optimization of the elastic thin plate under the temperature load is given.On the basis of this formula,the criterion method was used to construct an extended-spectrum containing temperature term.Using the variational method,an optimal iterative format for the thickness distribution with temperature correction term was deduced.Finally,several examples verify the effectiveness of the proposed method.In the study,different boundary conditions were considered,as well as the size and form of the structure,and an optimized design with different results was obtained.The second part of this thesis studies the iterative scheme of variable thickness optimization for cylindrical shell structures.Different from the thin plate structure,the displacement of the shell structure in the surface will cause internal force.The strain energy of the cylindrical shell structure is composed of two parts,that is,the bending strain energy and the membrane force strain energy.Analogous to the thin plate structure,the variable thickness optimization iteration scheme for increasing the temperature correction of column shell structure along the direction of busbar is derived.Finally,several common structures are used as numerical examples to verify the optimization criteria.In the study,different constraints,structural dimensions,etc.,which potentially affect the structural optimization design parameters,were considered and compared.In the third part,the variable thickness optimization iteration scheme for increasing the temperature correction term of general curved shell structures is studied,which can be applied to the shell structure with double curvature in the middle part.A number of irregular structures are considered in numerical examples.The numerical results show that the proposed optimization method can effectively reduce the thermal deformation and thermal stress of the shell structure.Finally,the paper looks forward to the next step in the possible research.