Integrated Design On Shape And Performance Of Porous Structure For Additive Manufacturing

Porous structure has a wide range of applications currently,owing to its high specific strength and its excellent performance in noise reduction,thermal insulation,energy absorption and shock absorption,etc.The development of additive manufacturing(AM)technology puts forward higher requirements for the design of porous structure,making it one of the research focuses that how to design the shape and properties of irregular porous structures.The irregularity of porous structure determines the complexity of design,which is mainly embodied in the following aspects:(1)Under the boundary constraints of complex surface,the trimming of infilling structure requires a large number of complicated calculations,leading to the difficulty in the modeling of porous structures.(2)Under mechanical constraints,it is difficult to achieve high specific strength in the design of porous structure while the macro-control ability of regular porous structures is poor,following low degree of freedom of strength optimization design.(3)Under the constraints of geometry and posture,the design method of static equilibrium is limited,making it unable to meet the requirement of printability for the existing structure.Aiming at the above difficulties,the boundary optimization algorithm of Voronoi tessellation is applied to the modeling of porous structures for designing a Voronoi framework according to the boundary characteristics.A kind of free porous structure is constructed by utilizing poles at the same time.Based on this,the strength optimization and balance optimization method of porous structures are studied in this paper,and AM is introduced to fabricate the porous structures.The main research contents and methods are as follows:(1)The modeling of porous structures based on boundary optimization.A Voronoi tessellation algorithm for any model with curved boundary and distinct features is proposed,where the 3D Voronoi diagram is employed as the framework of the porous structure design,and Voronoi sites are distributed on the internal and external surfaces of model in a many-for-one way.After fitting the boundary of the model by Voronoi polyhedron,the porous structure is modeled by poles.(2)The strength optimization design of porous structures.A strength optimization algorithm based on porous structures is proposed,which conducts weighted sampling for Voronoi sites on the basis of stress distribution to improve the calculation efficiency of strength optimization,and then adjusts the distribution and number of Voronoi sites iteratively.The adaptive Cauchy mutation is also employed to improve the local optimization capability of the algorithm,achieving high specific strength of porous structures.(3)The static balance optimization design of porous structures.A static balance optimization algorithm based on porous structures is proposed,where the barycenter of model is calculated by the layered method and different components and materials are taken into consideration to compute the barycenter accurately.The detection of support area is combined with the fission method of Voronoi sites set to generate the porous structure meeting the static balance requirements by iterations.In order to verify the proposed design method,a large number of STL models are adopted to be analyzed for each algorithm,which shows that the proposed method is efficient and convenient with well-fitted boundaries and reasonable strength and structural balance,meeting the design requirement preferably.