Research On Structural Topology Optimization Method Based On Additive Manufacturing Overhang Constraints

In recent years,additive manufacturing technology has gained widespread attention and rapid development,and it is expected to promote a new round of technological innovation in manufacturing.Making full use of the excellent properties of additive manufacturing to process almost any complex model and carrying out research on innovative design methods for additive manufacturing is an important way to realize the structural lightweight,design-oriented manufacturing and function-driven design.As an important means of structural innovation design,topology optimization can achieve the optimal material distribution can achieve optimal distribution of material under multi-load and multi-condition constraints.It not only can meet the application requirements of structural lightweight and performance improvement,but also can significantly reduce the material cost and increase the production efficiency.The combination of topology optimization design method and additive manufacturing technology can better exert the advantages of creativity and advanced manufacturing technology and optimize the structural design space.However,the traditional topology optimization design method does not sufficiently consider the new process constraint problem introduced by additive manufacturing technology,which is that the optimization result may have overhang regions or closed cavities.To ensure the stability of the manufacturing process,overhang area need to add support structure,which can not only reduce the forming efficiency but also lead to additional material consumption.How to effectively integrate manufacturing process constraints such as size,overhang and cavity constraints into the topology optimization process is the key issue to be considered in structural optimization design for additive manufacturing.In view of this,in this paper,the overhang constraint of additive manufacturing is taken as the research object,and the support minimization is taken as the design goal.The topology optimization design method of overhang constraints for additive manufacturing is studied.The contents and achievements are as follows:(1)The method of topology optimization design is summarized systematically,and the opportunities and challenges faced by the combination of additive manufacturing technology and topology optimization are discussed.Two topology optimization methods,SIMP and BESO,are analyzed and compared in detail,which provides a theoretical basis for the development of topology optimization algorithms based on the overhang constraints of additive manufacturing.(2)In view of the characteristics of SIMP topology optimization that there are intermediate density elements,a SIMP topology optimization method based on hierarchical filtering strategy is proposed.Theoretically,it can eliminate all the overhang area of the part,and can selectively retain the characteristic area in the filtering process to avoid the filtering operation changing the key structure.(3)Aiming at the characteristics of discrete design variables in BESO method,a BESO method based on overhang sensitivity analysis is proposed.According to the discrete nature of topology optimization,overhangs are expressed in terms of design variables.Then the overhang minimization is used as a new objective function in combination with the original optimization problem.The overhang sensitivity and other performance sensitivity are used as the basis for updating the design variables to reduce the overhang area in the optimization design.(4)The topology optimization design method proposed in this paper is applied to the complex three-dimensional parts such as satellite bracket and locking hinge.The feasibility and effectiveness of the algorithm are verified by comparing the size of the overhang area in the optimization scheme of original and improved algorithm.