Three-dimensional numerical simulation of selective laser melting process based on SPH method

Abstract

Selective laser melting (SLM) is an advanced, efficient and capable manufacturing technology that utilizes a laser for heating metal or alloy powders to melt and solidify directly into metal parts. In this paper, the smoothed particle hydrodynamics (SPH) method was employed for the three-dimensional numerical simulation of the SLM process. This method is significantly benefit for solving free surface flows and complex motions at multiple material phase interfaces. The weakly compressible equation of state and Navier-Stokes equation were used to describe the state and flow of the liquid metal in the process of the SLM mathematical modelling. The surface tension and wetting effect are critical for the morphology and evolution of the molten pool. A continuous surface tension model and a wetting effect model were established, and the correctness of these mathematical models was verified by the evolution of the liquid droplets over time. Then, a special material model was established based on the thermophysical properties of 304L stainless steel. A Gaussian heat source model was employed to heat the metal powder in the SLM process. In this work, the SPH method was used to simulate the morphology and formation of the molten pool at different laser powers and to analyse the effect of different laser powers on the size of the molten pool. The simulation results show that the surface tension and wetting effect under laser action play an important role in the expansion of the molten pool size; within a certain laser power range, the size of the molten pool gradually increases with increasing laser power, and the simulation calculation results are in good agreement with the experimental results. The results show that the SPH method is a viable and promising way to simulate the SLM process.