Multi-objective Topology Optimization Of Spatial Grid Structural Joints Based On Compromise Programming Method

Joints are important components in spatial structures,and the members are connected to form the structure through joints.At present,the common joint topology optimization design in spatial structure mainly focuses on single-objective design.For spatial structure,it is often in a complex stress state and many factors need to be considered in the design.Traditional design often considers single working conditions and goals.Therefore,to break through the conventional limits and make topology optimization effectively applied in spatial structure joints,multi-objective topology optimization design should be carried out for joints.In response to the above problems,this article introduces the basic idea of the variable density topology optimization method and uses the optimization software Opti Struct to perform topology optimization calculations on the web of an I-shaped beam on this basis,and obtains a new type of topology optimization beam structure.At the same time,the influence of the span-to-height ratio of the beam and the web height to thickness ratio on the optimized topological shape of the beam is considered.Compared with the traditional beam structure,the mechanical properties of the new beam are greatly improved.At the same time,the influence of the span/height ratio and height/thickness ratio of the web on the topological shape of the beam after optimization is taken into account.Compared with the traditional beam structure,the mechanical performance of the new beam is greatly improved.The results show that the web opening parameters have a greater impact on the performance of the beam.As the opening size increases,the beam failure modes are indicated: instability failure,flange shear failure,web shear buckling failure between holes,plastic strength failure at the connection of the holes.When designing,the structure should be designed so that a web shear a failure mode between holes should occur.Then,according to the above case method,the single-objective topology optimization design was carried out for the two joint forms.The optimization objectives were to minimize the structural flexibility under static single-case load and maximize the first three-order natural frequencies of the dynamic structure,and the single-objective optimization design is used to calculate the multi-objective topology optimization.In the optimization process,symmetry constraints,minimum component size constraints,checkerboard phenomenon control,and post-processing threshold selection were comprehensively considered,and the joint shape that satisfies each working condition was obtained,and the single-object multi-working condition optimization joint and single-objective were compared.It can be seen that under the constraints of static topology optimization with the goal of maximizing structural stiffness,the mechanical performance of multi-condition optimization is more balanced than that of single-condition optimization.Based on single-objective optimization,a multi-objective function of the joint is constructed by considering both the maximum stiffness objective and the maximum low-order frequency objective,and the multi-objective topology optimization method is used to analyze the two joints,and the two joints are simultaneously satisfied.A new type of joint topology for static and dynamic targets.Using the Poly-Nurbs modeling method in Solid Thinking Evolve to remodel the optimized joints,a smoother joint was obtained.The mechanical properties of multi-objective and single-objective optimized joints and hollow sphere joints are compared.The results show that,compared with the traditional optimized joint,the structure obtained by multi-objective optimization can meet the requirements of multiple objectives and working conditions at the same time.The mechanical properties of the joint obtained after multi-objective optimization are better than that of the hollow spherical joint,and the stress distribution is more uniform.Based on the above research,finally,the topology optimized joint is combined with additive manufacturing.The additive manufacturing technology breaks the limitations of traditional casting.For complex components,the manufacturing speed is faster and the model obtained is more accurate.The combination of additive manufacturing and joints multi-objective topology optimization will surely realize the industrial application of joints successfully...