考虑熔池流动效应的选区激光熔化温度场模拟研究

Simulation of Temperature Field in Selective Laser Melting Considering Melt Pool Flow Effect

利用有限单元法模拟选区激光熔化(selective laser melting,SLM)单道成形过程,建立热流耦合模型,考虑了固体金属材料性质随温度变化和相变过程,以及粉末间隙对材料性质的影响。利用焓-孔隙度方法模拟熔池凝固时的动量耗散,确定固-液相界面。根据能量守恒定律,在现有的圆柱体热源模型上,提出了旋转抛物体热源模型,并与传统高斯面热源模型选区激光熔化过程中温度分布和熔池尺寸的预测结果比较。结果表明,在试验激光能量密度研究范围内,旋转抛物体热源和高斯面热源模式下熔池宽度的平均预测误差分别为12.18%、7.07%。对于熔池宽度,高斯面热源的预测精度优于旋转抛物体热源。当激光能量密度为40~100 J/mm^(3)时,旋转抛物体热源和高斯面热源模式下熔池深度的平均预测误差分别为17.00%和38.20%。对于熔池深度来讲,旋转抛物体热源预测精度优于高斯面热源。此外,研究发现考虑熔池流动效应作用下得到的熔池温度分布更加均匀。

This paper presents the simulation of temperature in single-track selective laser melting(SLM).The properties of solid metal materials changing with temperature and the phase transition process,as well as the effect of porosity of the metal powder on material properties are considered.The enthalpy-porosity method is adopted to simulate the momentum dissipation during solidification of the melt pool,and the solid-liquid interface is determined.According to the Law of Conservation of Energy,a Parabolic Optical Penetration Depth(POPD)volumetric heat source method is proposed based on the existing cylinder heat source method.The prediction results of the temperature distribution and the melt pool size are compared between the traditional Gaussian surface heat source model and the POPD volumetric heat source model.The results show that the average prediction errors of the molten pool width are 12.18%for the POPD volumetric heat source model,and 7.07%for the traditional Gaussian surface heat source model within the explored laser energy density range.With respect to the width of the molten pool,the prediction accuracy of Gaussian surface heat source is better than that of POPD volumetric heat source mode.When the laser energy density is between 40~100 J/mm^(3),the average prediction errors of the melt pool depth are 17.00%for the POPD volumetric heat source model,and 38.20%for the traditional Gaussian surface heat source model.With respect to the depth of the molten pool,the prediction accuracy of the POPD volumetric heat source is superior to the Gaussian surface heat source mode.In addition,it is found that the melt pool temperature distribution is much more uniform when considering the melt pool flow effect.