Research On Topology Optimization Design And 3D Printing Manufacturing Of Cast Steel Joints With Branches

With the continuous improvement of modern building technology,the large-span spatial structure system is becoming more and more complex.Many members cross at same joints,welding connection is inconvenient and the residual stress is large.Due to the technical characteristics of integral casting,cast steel branch joints can accurately control the number of branch pipes,branch angles and sizes,realize the smooth and beautiful appearance of the joint.At the same time,it can transfer the welding part between joints and members outside the joint area,eliminate the residual stress generated when the structure is welded in the intersection area of multiple members,significantly reduce the construction difficulty,and improve the construction speed and quality.However,the level of optimization design and manufacturing technology of cast steel branch joints is still low.Insufficient design optimization of the joints results in stress concentration at the junction of the members.The weight of the joint is very large,the amount of steel used is excessive,and the production and transportation costs are high.The production and manufacturing of joints technology is backward,and the traditional process of manufacturing core mold,sand box,molten steel pouring,heat treatment and grinding is still adopted.The complicated procedures,low manufacturing accuracy,long construction period,high cost,low energy saving and environmental protection have made it difficult to meet the requirements of modern engineering practice.Aiming at the above problems in the design and manufacturing process of cast steel branch joints,cast steel two-branches,three-branches,and four-branches joints were selected as objects in this paper.The optimal topology shape of cast steel branch joints was studied by using topology optimization method,and the intelligent manufacturing method of cast steel branch joints was explored using 3D printing manufacturing technology.Firstly,the original model of cast steel branch joint was established by using Solid Works 3D modeling software,and the Opti Struct solver in Hyper Works finite element software was used to topology optimize the cast steel branch joint.The influence of optimization parameters such as penalty factor and checkerboard control on the optimization results was discussed.The element density cloud map and element isosurface map of the optimized model were obtained.The optimal topological model of the cast steel branch joint was obtained after repeated comparison and debugging.Secondly,the mechanical properties of the topologically optimized joints and the original cast steel branch joints were analyzed and compared.It is proved that the topology optimization method can significantly reduce the self-weight of the cast steel joints and improve the design optimization level while maintaining the good mechanical properties of the joints.The obtained optimal topology optimization joint was compared with the welded hollow ball joint and treelike joint commonly used in engineering,and it is obtained that the topology optimization joint has the best mechanical performance.It is effective and feasible to find the best shape of the cast steel joint by the topology optimization method.Thirdly,based on the model features of the topology optimization joint,a new type of joint was artificial designed,its mechanical properties were analyzed,and compared with the topology optimization joint,new design ideas for future joints were explored.Then,two joints used in practical engineering were selected as examples,and topology optimization methods were used to perform shape-finding design.The mechanical properties of the optimized joints were compared with the original joints.The weight is reduced and the mechanical performance was improved,which again confirms the rationality and feasibility of finding the optimal model of the structure using the principle of topology optimization.Finally,the technology and equipment overview of 3D printing in the construction field were discussed.The scale model of the topology optimization joint was manufactured using 3D printing manufacturing methods such as FDM technology,SLM technology,and Rapid Casting Process.Compared with the traditional manufacturing process,the layer-by-layer printing technical characteristics of 3D printing manufacturing are not limited by the appearance of the model,which is very suitable for manufacturing topology optimization joints with complex shapes.Applying 3D printing technology to joint manufacturing can not only significantly increase the production speed and improve the manufacturing accuracy,but also solve the key problem that the complex shape formed by topology optimization are difficult to manufacture by traditional technology.