Three-Dimensional Numerical Simulation Of Selective Laser Melting Process Based On SPH Method

Selective Laser Melting(SLM)is a fast,efficient and powerful manufacturing technology which uses Laser heating alloy powder to melt and solidify metal parts directly.It has been widely concerned by domestic and foreign researchers.But in the forming process,due to the fast scanning speed,high power density and the change of metal powder among solid phase,liquid phase and solid phase in a short period of time,the temperature field distribution in SLM process is uneven and the temperature gradient is large,resulting in a series of defects in SLM process.However,exploration only through experimental methods will consume a lot of financial resources and manpower,and the numerical simulation method has received more and more attention.Therefore,it is of great significance to use numerical simulation method to study SLM process.At present,most of SLM simulation research is based on grid method.However,large deformation and mesh reconstruction in the process of calculation will lead to the decrease of calculation accuracy.In this paper,the Smoothed Particle Hydrodynamics(SPH)method is used to make a three-dimensional numerical simulation of the micro-scale SLM process.Because SPH method is completely independent of grid division,it has great advantages in dealing with multiphase flow and free surface flow,so the numerical simulation of SLM process using SPH method shows a great development prospect.This paper adopts SPH method to study SLM process simulation mainly as follows:According to the basic theory of SPH method,a three-dimensional mathematical model of SLM process based on SPH method is established.Weakly compressible state equation and Navier-Stokes equation were used to describe the state and flow of metal liquid.Surface tension plays an important role in the shape and evolution of molten pool.The model of continuous surface tension and wetting effect is established.According to the thermal and physical properties of 316 L stainless steel,a special material model was established.The Marangoni convection effect is written into the simulation program.A Gaussian energy model was used to heat the metal powder.According to the mathematical model established in this paper,the SLM process is numerically simulated,and the morphology changes of the molten pool in different time periods of the single-pass SLM simulation process and the physical characteristics of the molten pool deposition process are discussed.Different laser power is used to conduct numerical simulation research on the SLM process and the influence on the molten pool size is discussed.The accuracy and correctness of SPH method for SLM process simulation are further verified by comparing the simulation results of SPH method with the simulation results of finite element simulation software and experimental data,which provides a solution for the numerical simulation of SLM process and has certain engineering application value.