Numerical Simulation And Experimental Research On Temperature Field And Stress Field Of Selective Laser Melting 316L

Selective laser melting is one of the additive manufacturing technologies,which is characterized by fast heating and cooling in the forming process,resulting in porosity,warpage,and even cracking and scrap in the forming process,especially in the pendant hole bridge structure with special shape.The temperature field and stress field coupling analysis and forming quality study are carried out by ANSYS finite element analysis software for the selected area laser melting forming process of316 L stainless steel.Firstly,based on the physical properties of materials such as thermal properties,combined with the influencing factors of heat source selection,cooling time and convective heat transfer,a numerical model of single layer and single channel selected laser melting and forming is established by finite element parametric design language,and the effects of laser power,scanning speed,preheating temperature and line energy density on the temperature and stress fields of single channel are investigated.The results show that the internal temperature and melt pool size are positively correlated with the laser power,preheating temperature and line energy density,and negatively correlated with the scanning speed;the thermal stress is positively correlated with the laser power,scanning speed and line energy density,and negatively correlated with the preheating temperature.Secondly,the evolution law of temperature and stress fields in multilayer multi-channels is studied.The results show that there is a temperature thermal cycling curve in the multilayer multichannel temperature field.Due to the thermal accumulation effect,the maximum temperature of the upper layer is larger than that of the lower layer,which gradually stabilizes with the increase of the number of layers;the rate of temperature change increases with the increase of laser power;the stress magnitude decreases with the increase of the number of scanning tracks,and the stress distribution shows a periodic change,forming an inner concave in the middle and warping around after cooling.The linear and serpentine scans are basically the same in terms of stress magnitude and stress distribution.Third,the effects of different scanning paths on the stress field and deformation of the overhanging hole bridge structure are investigated.The results show that the scanning method of varying the scanning deflection angle by 90° per layer produces a shorter period and smaller amplitude of the thermal stress cycling curve than the linear scanning method,and produces less stress and deformation at the overhanging hole bridge.Finally,the effect of process parameters on the forming quality of 316 L was investigated.The results show that the energy density is 250 J/m and the scanning mode is 90° scanning deflection angle per layer,the denseness reaches 99.2% and the dimensional accuracy is 0.016 mm.The highest dimensional accuracy of the formed pendant structure is obtained by the test.The error between the test results and simulation is about 9%,and the simulation is accurate and reliable.