Multi-objective Topology Optimization Of Thermal-mechanical Structure Based On Meshless Method And Parameterized Level Set Method

Orthotropic structures have been widely used in mechanical and power engineering and other fields due to its excellent mechanics and heat transfer performance,and its working environments mostly involves multi-physics.Therefore,the multi-objective topology optimization design of orthotropic structures is of great significance to the practical application of engineering structures,which can obtain the topological structure with the best comprehensive performance according to different design requirements.However,the topology optimization method based on material distribution model often has some problems,such as jagged border,checkerboard and gray element,etc.Therefore,the optimized structure is difficult to manufacture directly.The topology optimization method based on the parameterized level set method(PLSM)and the element-free Galerkin method(EFG)can effectively solve these problems.The topological structure has clear boundary,which is convenient for manufacturing.At the same time,it overcomes the numerical difficulties of the traditional level set method.In this paper,the topology optimization method based on the EFG method and PLSM is applied to the static topology optimization,the heat transfer topology optimization,and the multi-objective topology optimization for thermo-mechanical coupling of orthotropic structures.The main research work is as follows:(1)The static topology optimization design of orthotropic structures based on EFG method and PLSM is studied.The minimum compliance topology optimization model of the orthotropic structure was established.And the influences of Poisson's ratio factor and off-angle on the EFG optimal topology and compliance were discussed.The mechanical properties of orthotropic and isotropic structures under a set of optimal parameters were compared.The results show that the topology optimization model can get clear and smooth topology boundary,which is easy to manufacture.Compliance increases with the increase of Poisson's ratio factor,while off-angle has little effect on it.It is suggested that the reasonable range of Poisson's ratio factor for orthotropic L-shaped beam and hook is 0.65?1.Compared with the isotropic structures,the compliances of the orthotropic L-shaped beam and the hook are reduced by 21.6% and 24.3%,respectively,reflecting the advantages at the deformation resistance of orthotropic structure.(2)The heat transfer topology optimization design of the orthotropic structure based on EFG method and PLSM is studied.The minimum heat dissipation topology optimization model of the orthotropic structure was established.And the influences of thermal conductivity factor and off-angle on the EFG optimal topology and heat dissipation were discussed.The heat transfer performance of the orthotropic structure and the isotropic structure under a set of optimal parameters were compared.The results show that the recommended value ranges for the thermal conductivity factor of the orthotropic L-shaped beam and the orthotropic tube heat exchanger are 0.7?1.25 and 0.1?1 respectively,and the off-angle can be determined according to the specific design requirements.The maximum temperature and heat dissipation of the orthotropic structure are lower than those of the isotropic structure.(3)The multi-objective topology optimization design for thermo-mechanical coupling of orthotropic structure based on EFG method and PLSM is studied.The topology optimization model was established,that the weighted function of compliance and heat dissipation were chosen as the objective function.The influence of weight coefficient,off-angle,Poisson's ratio factor and thermal conductivity factor on the multi-objective optimal topological structure and objective function value were discussed.The mechanical and heat transfer properties of orthotropic and isotropic structures were compared.The results show that the recommended ranges of Poisson's ratio factor and thermal conductivity factor for orthotropic brake disc are0.1?1 and 0.65?2,respectively.Compared with the isotropic structure,the weighted objective function and compliance of orthotropic brake disc are reduced by 13.1% and 8.7%,respectively.In this paper,the static topology optimization,heat transfer topology optimization and thermo mechanical coupling multi-objective topology optimization of orthotropic structures based on EFG method and PLSM are studied.The obtained optimal topological structure has clear boundaries and is easy to process and manufacture.The orthotropic structures have better mechanical and heat transfer performance than isotropic structures,that has important engineering application value for the lightweight design of multi-physics orthotropic structures.