Simulation And Experimental Study On Residual Stress And Distortion In Selective Laser Melting Of Thin-walled Curved Surface

In recent years,the rapid development of advanced manufacturing technology in China has put forward higher requirements for the production efficiency and quality of key equipment parts.As one of the key technologies of metal additive manufacturing,Selective Laser Melting(SLM)is widely used in aerospace field because of its integrated forming and lightweight characteristics.However,the SLM forming process is accompanied by complex temperature gradient and stress changes,resulting in defects such as spheroidization,pores,and cracks in the forming area of the part,so that the forming quality cannot directly meet the use requirements.In this paper,based on the thermal elastic-plastic model and the inherent strain model,the simulation and experimental research of SLM non-solid support structure and thin-walled curved parts are carried out.The main work includes:(1)The finite element model of SLM forming process was constructed by using laser heat source model,thermal elastic-plastic model,inherent strain model,yield criterion and strengthening criterion,and the corresponding material parameters were set.(2)The SLM experimental study on the forming quality of parts was carried out.The effects of laser power,scanning speed and scanning distance on the forming quality of Al Si10 Mg alloy powder were investigated.The formation mechanism of parts spheroidization,pores and cracks under different forming parameters is analyzed,which provides a reference for the forming parameters of thin-walled curved parts.(3)The simulation of support structure based on thermal elastic-plastic model was conducted.The geometric structure and forming laser power parameters of the non-entity support were designed.The relationship between the internal residual stress of the support and its connection effect was analyzed.The change rules of the support connection under different forming conditions were compared.Based on the support connection effect,the support geometric structure and laser power parameters were optimized.It is prepared for the subsequent research on the influence of support on the residual stress and distortion of thin-walled curved parts.(4)The thin-walled curved feature parts are designed,and the residual stress and distortion distribution of the thin-walled curved parts after forming are simulated based on the inherent strain model.Comparing the residual stress of the parts after self-forming and adding support,it is found that the Z-direction normal stress is the main influencing factor of the residual stress distribution of the parts.The residual stress and distortion evolution of parts under different thicknesses and forming heights were studied.The experiment of SLM forming thin-walled curved parts was carried out.The geometric data of the parts were obtained by three-dimensional scanning instrument,and the distortion simulation results of the formed parts were verified and analyzed.