Research On Topology Optimization Method Considering Support Constraints In Additive Manufacturing

In recent decades,topology optimization has become an important method of innovative structural design,which can create high quality and novel innovative design without relying on the experience of designers.At the same time,the additive manufacturing technology realizes the free growth molding of complex structures by means of material layer-by-layer accumulation,which largely eliminates the limitation of geometric complexity and makes up for the shortcoming that the topology optimization design is difficult to fabricate by traditional manufacturing process.Additive manufacturing is highly compatible with the topology optimization method.The combination of topology optimization and additive manufacturing has become a trend,which has broad prospects.On the one hand,additive manufacturing provides convenience for the practical engineering application of topology optimization,but on the other hand,it also presents unique requirements and challenges for topology optimization method.The classical topology optimization method does not consider the process characteristics of additive manufacturing,resulting in the need of additional support materials when the optimization results are manufactured,which increased the cost and difficulty of manufacturing and cleaning of the support structure.In order to solve the above problems,this thesis studies the support constraints of additive manufacturing in the framework of density-based topology optimization.For the case of self-supporting(having no support structure)and that of having support structure in which the self-supporting structure cannot meet the design requirements,this thesis proposes two complementary topology optimization methods for additive manufacturing.The specific research contents of this thesis are as follows:(1)The basic theory of topology optimization based on variable density method is studied.The efficiency and application range of different solution methods are discussed.Aiming at the numerical instability phenomenon in variable density method,an improved sensitivity filtering method is proposed.The density gradient weights are included in the sensitivity filtering formula to obtain clear structural boundaries,which is conducive to the extraction and manufacture of the optimized results.The versatility and effectiveness of the method are verified in several typical numerical examples.(2)For the SLM(Selective Laser Melting)technology of additive manufacturing,the minimum overhang angle of self-supporting structure is studied.The angle constraint is transformed into the constraints related to the design variable,and the local self-supporting constraints are transformed into a global constraint based on the constrained aggregation method.The global constraint is integrated into the topology optimization model.Finally,the effectiveness of the method is verified by the MMA(Method of Moving Asymptotes)alg orithm in a typical numerical example,and the influence of the optimization parameters on the optimization results is discussed.(3)A computational model of the support structure volume is constructed and introduced as a unique constraint into the density-based 3D continuum structure topology optimization model.In a typical example,the control effect of the optimization parameters on the support volume of the optimization results is analyzed,and the effectiveness of the method is proved.Static analysis is performed on the topology optimization results to verify that the equivalent stress and global displacement meet the strength requirements.Based on the combination of theoretical analysis and numerical verification,this thesis verifies the effectiveness of the proposed method through several numerical examples,and provides an important reference for the practical application of innovative structural design and topology optimization for additive manufacturing.