Mesoscopic Simulation And Parametric Analysis Of Selective Laser Melting Process Of Stainless Steel

Selective laser melting process are influenced by many factors.Moreover,using trial and error methods to determine the process parameters is expensive and timeconsuming during the experiment.It's also difficult to figure out the complex physics in the molten pool.In this paper,a multi-physics mesoscopic model is proposed to simulate selective laser melting process,which is used to study the metal powder bed formation process,the physics of molten pool and the mechanism of defects.A complete discrete element model,including algorithm model and geometric model is built to simulate the powder bed generation process using Yade software.Relative packing density(RPD)and relative un-uniformity ratio(RUR)are defined to characterize the quality of powder bed quantitatively.The effects of the layering thickness,the spreading speed of blade and the particle size distribution of metallic powders on the quality of the powder bed are investigated.The powder bed model obtained in DEM simulation is imported into FLOW-3D software as the initial model to study the particle melting,molten pool flow and solidification process.The effects of laser power and laser scan speed on single tracks are investigated.Moreover,the mechanisms of single tracks defects,including balling defects,necking defects and porosity defects,and the thermodynamic and kinetic of molten pool are systematically elaborated.The surface morphology and the size of molten pool are analyzed while power is changed.The electric signal detection method is used to determine whether the track is keyhole mode,which provides a new sight for the porosity detection.The surface topography of tracks and temperature field of molten pool are simulated under different parameter combination while liner energy density(LED)is constant,and the results reveals the mechanism of small angle distortion defects.The morphology and size of the single tracks is studied by experiments.The effect of hatch space on surface topography,internal connectivity,temperature field of successive tracks is investigated and the energy efficiency is quantitatively discussed.Different scanning method are compared with each other,and the difference of tracks under various packing density of powder bed is also analyzed.