Research On Optimization Design Method Of Special-shaped Three-dimensional Lattice Structure Based On Thermal Load Constraints

Lattice structure is a spatial ordered porous structure composed of periodic cells arranged according to certain rules.It not only has high specific strength,high specific stiffness,high toughness,high energy absorption and other excellent mechanical properties,but also has good thermal insulation and thermal dissipation,noise reduction,damping and shock absorption,electromagnetic shielding and other special functions.Its excellent structural properties make it has a wide application prospect in aerospace,mold design,biomedical and other fields.In this thesis,the optimization design of thermal insulation performance of Triply Periodic Minimal Surfaces(TPMS)lattice structure is taken as the goal.The method of structural design,numerical simulation and physical experiment is combined to solve the coupled thermal transfer problems of thermal conduction,convection and radiation thermal transfer of the TPMS lattice structure.The thermal insulation performance differences of four typical TPMS lattice structures such as Diamond,Gyroid,IW and Tub-Primitive are studied.The influence of relative density and cell size on thermal insulation performance is analyzed.Based on the optimization strategy of variable density and gradient cell size,the optimal design of thermal insulation TPMS lattice structure is realized.The main work of this thesis is as follows:(1)The TPMS modeling method based on implicit function and the solid modeling method based on MC algorithm are studied,and the geometric modeling of diamond,gyroid,IW and tub primitive is realized.Based on the theory of finite element analysis of temperature field,the thermal insulation model of TPMS lattice structure is established,and the thermophysical parameters,initialization and boundary conditions of related materials were given.(2)Based on the numerical simulation method,the effects of cell number effect,cell configuration,relative density and cell size on the thermal insulation performance of TPMS lattice structure were studied.In the process of lattice thermal transfer,the lower the thermal conduction efficiency and the more the thermal loss,the lower the temperature of the bottom panel,the higher the thermal insulation efficiency and the better the thermal insulation performance.Through comparative analysis,the difference of the thermal insulation performance of four kinds of TPMS lattice structure is obtained as follows: Diamond>IW>Gyroid >Tub-Primitive.The range of the thermal insulation efficiency of the D lattice structure with 20%-60% relative density is 26.17%-55.29% under the conditions of considering thermal conduction,thermal convection and thermal radiation.With the increase of the relative density,the temperature of the bottom panel increases and the thermal insulation performance decreases.The thermal insulation efficiency of the 3.33-10 mm cell lattice ranges from 47.89% to 61.37%under the conditions of thermal conduction,thermal convection and thermal radiation.With the increase of the cell size,the surface area of the structure decreases and the thermal dissipation capacity decreases greatly,while the temperature of the bottom panel increases and the thermal insulation performance decreases.(3)Aiming at the requirement of optimal design for thermal insulation performance of TPMS lattice structure,an optimal design method for thermal insulation performance of TPMS lattice structure based on equivalent thermal resistance evaluation was proposed.The equivalent thermal resistance of cell is calculated by using the method of slice integration,and the equivalent thermal resistance of lattice structures is derived by using the method of series parallel calculation of equivalent resistances,and the prediction of the thermal insulation performance of the lattice structure is realized.Combined with the optimization design method of variable density and gradient cell size,the optimization design of thermal insulation performance of the TPMS lattice structure is realized.Through numerical simulation analysis,taking the thermal insulation panel structure as an example,the improvement effect of the optimization design method on the thermal insulation performance of lattice structure is verified.Compared with the solid structure,the thermal insulation efficiency of the optimized structure with variable density and gradient cell size optimization structure can be increased by 14.74%and 13.25% respectively.(4)In order to verify the conclusion of numerical analysis,a set of thermal transfer system is designed,and a series of thermal transfer experiments are carried out.By comparing the experimental data with the simulation results,the influence of the form of TPMS lattice structure on its thermal insulation performance is verified.