Research On Structural Topology Optimization Design Considering The Residual Deformation Of 3D Printing

The topological optimization design method can search for the best spatial distribution of materials,which has great design freedom and can realize the design of high-performance and lightweight structures.However,the structure obtained by topology optimization method is often complex,and traditional manufacturing technology is difficult to manufacture.Different from traditional manufacturing technology,3D printing technology is a process of layer-by-layer stacking of materials that can print any complex structure,providing the possibility of manufacturing topologically optimized structures.However,in the metal 3D printing forming process,the rapid melting and solidification of metal powder will produce sudden temperature gradient,which will inevitably produce residual deformation.The accumulated excessive residual deformation will lead to deformation,cracking and other defects of the printed part.In response this problem,based on topology optimization method,this paper considers the influence of metal3 D printing residual deformation in the structural design stage,and carries out 3D print-oriented topology optimization method research.The main work includes:A thermal-solid coupling model of layer-to-layer and intra-layer melting process with a reciprocating scanning path for selective laser melting(SLM)technology is established using ABAQUS finite element software.The load and directional movement of the laser heat source are implemented by DFLUX subroutine.The “life and death” element technology is used to simulate the melting and stacking process of metal powder during the printing process,realizing numerical simulation of the metal 3D printing process.Based on this,the distribution and variation of temperature and strain during the single-layer multi-path and multi-layer multi-path printing processes are analyzed.The traditional inherent strain method(ISM)is modified,and the equivalent modified inherent strain load is extracted from the thermal-solid coupling model,and the equivalent load is applied layer by layer to the elastic finite element model to achieve efficient simulation of the metal 3D printing process.The accuracy and efficiency of the modified inherent strain method in predicting 3D printing residual deformation are verified by comparing the results of the 3D printing experiment,laying a theoretical foundation for the subsequent research on the integration of topology optimization design and 3D printing manufacturing.To address the residual deformation problem in the metal 3D printing process,through introducing the P-norm of global residual deformation and deducing its sensitivity,a multiobjective optimization algorithm is proposed to improve the design and manufacturing performances,namely minimize metal 3D printing residual deformation and structural compliance simultaneously based on the floating projection topology optimization(FPTO)method and inherent strain theory.Several 2D and 3D examples are conducted to demonstrate the effectiveness and applicability of the method proposed.