Topological Optimization Design And Selective Laser Melting Manufacturing Of Porous Structures With Variable Density

The porous structure has a broad application prospect in the design fields of lightweight,energy absorption,earthquake resistance,and noise reduction.However,the complex structure of a porous cell is difficult to be formed by traditional machining methods.Additive manufacturing technology has the advantage of forming extremely complex structures.The processing cost does not increase obviously with the increase of component complexity,which greatly improves the design freedom of complex porous structures and provides the possibility for the application of porous structures.Structural topology optimization can obtain the optimal material distribution in the design domain under the constraints of target performance and boundary conditions,which is very suitable for designing new porous structure cells.This paper proposed a design method of porous structure with variable density based on topology optimization.In order to analyze the mechanical properties of the designed cells,Selective Laser melting(SLM)technology in additive manufacturing was used to construct and shape the cells with porous structure rapidly.Then the mechanical properties of porous structures were investigated by combining quasi-static compression experiment and numerical simulation.Finally,the designed cell and the proposed variable density porous structure design method were applied to engineering examples,which can provide a reference for lightweight design in aerospace,shipbuilding,and automobile fields.The main research contents of this paper are as follows:Firstly,the SLM process was studied to obtain stable mechanical properties of porous structure cells: the optimal combination of laser power,scanning speed,and scanning distance were explored by orthogonal experiment with block density as the optimization objective.The quality of SLM molding parts under the optimal process parameters was quantitatively studied by confocal laser microscope observation,density measurement,and mechanical tensile properties test.The 316 L mechanical parameters of SLM molding were obtained to prepare subsequent cellular mechanical properties analysis.Secondly,the level set topology optimization technology was adopted to optimize the porous cell structures of VL,ECL,PTL,and FTL with four different configurations for four specific working conditions,taking the maximum stiffness as the objective and the material volume as the constraint condition.The Gibson-Ashby model was obtained by analyzing and designing the stress-strain response of cell structure through a quasi-static compression experiment.Finite element numerical simulation was used to analyze the deformation behavior and failure process of cell structure under quasi-static compression.Then,a design method of variable density porous structure based on topology optimization is proposed.The topological optimization model of the overall material density distribution of SIMP was established.The sensitivity analysis of design variables and OC algorithm were used to update the element density iteratively to obtain the overall optimal material distribution.According to the coordinate information,the cells of the designed porous structure were filled with variable density in different regions to complete the design of the porous structure with variable density.A three-point bending beam was used as a model to show the specific design process and SLM printing.The mechanical properties of variable-density and uniform porous structures were compared through the three-point bending experiment and numerical simulation.Finally,the variable density porous structure design method was applied to an engineering example.The aircraft bearing support was obtained as the original model and the optimized model by designing a variable density porous structure.The numerical simulation showed that optimized model mass was reduced by 45% under the premise of meeting the strength requirements.The lightweight design of the structure was realized.The SLM manufacturing optimization model has good manufacturability,which proved the effectiveness of the design scheme of variable density porous structure.