Research On Topology Optimization Method Of Thermo-elastic Problems For Additive Manufacturing

The combination of topology optimization technology and additive manufacturing technology can not only bring into play the technical advantages of additive manufacturing methods in manufacturing complex structures,but also enable the optimal structure obtained by topology optimization.In process of the SLM,the structure is prone to warp deformation due to heat,and the structural overhang portion is prone to collapse during the additive manufacturing process,so the support structure is required to successfully complete the printing,which not only causes waste of materials,but also increases the difficulty of postprocessing of the structure.In the traditional structural topology optimization,the structural optimization is carried out under working conditions,the optimized results are not considered in the thermal load problem during the additive manufacturing process,and the structural accuracy of the part cannot be guaranteed without considering the large thermal deformation caused by the heat.Furthermore,based on the variable density topology optimization method,there are a large number of intermediate density units at the boundary of the optimization results,which makes the structure boundaries unclear and cannot be directly used for additive manufacturing.In order to solve the above problems,this thesis will carry out research on SLM process analysis,structural optimization under thermal load of additive manufacturing,structural boundary treatment and structural self-supporting design.The main work contents are as follows:Firstly,the theories of structural transient heat conduction analysis and stress deformation analysis are studied.Based on ANSYS software,the finite element analysis model of temperature field and stress field for slab-shaped thin-walled multi-layer forming is established.The evolution process of temperature distribution and stress distribution inside the structure during SLM molding is explored.Secondly,the structural topology optimization method considering the additive manufacturing thermal load is studied.The finite element analysis theory of thermos-elastic problem is studied,and the finite element equilibrium equation of thermos-elastic problem is derived.The topology optimization model of thermos-elastic problem based on RAMP model is established.Based on the thermal load of the structural temperature distribution at the end of structural forming in the SLM temperature field analysis,the topography of the plate structure is optimized,and an improved sensitivity filtering method is used to identify the structural boundary elements by density gradient information and weaken the filtering effect for the boundary elements.The filtering process is used to obtain an optimal structure with clear boundaries.Thirdly,a multi-material topology optimization method considering the additive manufacturing thermal load is studied.Based on the variable density multiphase material description method,the thermal coupling topology optimization model of multi-materials is established.The multiphase material plate structure is optimized under the thermal load obtained by SLM analysis,and the improved sensitivity filtering method is adopted to suppress interference between different materials in order to get the clear boundaries between different materials.fourthly,the topology optimization method with structural self-supporting treatment and heating conditions for additive manufacturing is studied.The structural processing method for self-supporting is introduced into the thermal coupling topology optimization process,and the temperature distribution obtained by the SLM process analysis is used as the thermal load to make the optimization of the plate structure,so that the optimized result not only can be self-supporting in the additive manufacturing process,but also takes into account the structural properties under thermal loading.Structural boundaries are processed using improved filtering methods.Finally,the thesis summarizes the research content of the full text,and expounds the shortcomings and the direction in which the research can continue.