Study On Topology Optimization Based On The Overhang Constraint Of Selective Laser Melting

As a typical rapid melt forming technology,selective laser melting(SLM)provides a new method for the integrated fabrication of complex structures.Topology optimization is an automatic optimization design tool that mainly studies the optimal layout of structural materials according to optimization goals and geometric constraints.Therefore,the combination of topology optimization and SLM creates opportunities for lightweight design and manufacturing of structures,but the existence of the overhang constraint seriously restricts the property of topology-optimized structures.Hence,the paper deeply researches the design method,experimental verification and secondary development about topology optimization of the Ti6Al4 V topology-optimized structures based on the overhang constraint of SLM.The major contents and conclusions are exhibited as follows:(1)The topology optimization method based on the SLM overhang constraint is studied.The method of the overhang filter is introduced in detail.Then the work establishes the topology optimization model of considering the SLM multi-angle overhang constraint based on SIMP method.Several 2D and 3D examples are implemented to demonstrate the feasibility and effectiveness of the proposed method applied to the theoretical selfsupporting design.(2)The formability and mechanical behavior of the topology-optimized structures based on the SLM overhang constraint are studied.Taking Messerschmidt–B(?)lkow–Blohm(MBB)beam as an example,the design,forming quality and mechanical properties of the self-supporting topology-optimized structures are analyzed and compared in detail.The results show that the topology-optimized structures using SLM have good forming quality and mechanical properties.When the volume fraction f >0.3,the MBB beam can be manufactured successfully by SLM,and the forming quality of MBB beams is good.When f=0.4-0.7,the constant-section MBB beams(2D,CS-MBB)have two failure modes of the failure of the thin rods in the structures and the crushing failure on the loading position.While the variable-section MBB beams(3D,VS-MBB)have only one failure mode for the crushing failure on the loading position.The comprehensive performance of the VS-MBB beams is better than that of the CS-MBB beams.When f is around 0.4,the VS-MBB beams have the best formability and the highest specific stiffness.The ABAQUS simulation results match well with those of the experiments within 15% relative error.(3)The secondary development of topology optimization for SLM oriented the overhang constraint is produced.A plug-in for topological optimization of the overhang constraint is developed under the ABAQUS secondary development tools Python and MATLAB,and the self-supporting topology optimization design of three examples considering the overhang constraint is realized,which will provide a guidance in future researches.