1 © 2020 by ASME Proceedings IMECE2020 2020 ASME International Mechanical Engineering Congress and Exposition USA IMECE2020-23550 3D MODELING OF ADDITIVE MANUFACTURING PROCESS: THE CASE OF POLYMER LASER SINTERING Lan Zhang 1 , M’hamed Boutaous 1 , Shihe Xin 1 , Dennis A. Siginer 2 Univ Lyon, CNRS, INSA-Lyon, Université Claude Bernard Lyon 1, CETHIL UMR5008, F-69621, Villeurbanne, France Email: mhamed.boutaous@insa-lyon.fr, Lan.zheng@insa-lyon.fr, shihe.xin@insa-lyon.fr 2 Centro de Investigación en Creatividad y Educación Superior y Departamento de Ingeniería Mecánica Universidad de Santiago de Chile, Santiago, Chile Email: dennis.siginer@usach.cl ABSTRACT This work focusses on studying multiphysical transient phenomena in polymer powders occurring during selective laser sintering in polymers powders. Multiple phenomena stemming from the interaction of the laser with the polymer powder bed and the transfer of the laser power to the powder bed including laser scattering and absorption, polymer heating, melting, coalescence, densification, and the variation of the material parameters with the temperature are simulated via the modified Monte Carlo-ray tracing method coupled with the Mie theory. A finite volume method is adopted for the heat transfer. The model couples heat diffusion, melting, coalescence and densification of the polymer grains, and the crystallization kinetics during the cooling steps. Laser intensity is concentrated on the surface of the material contrary to the predictions of the Beer-Lambert law. Laser acting on thermoplastic material cause the polymer powder melt, coalescence between melted grains, air diffusion versus densification, crystallization and volume shrinkage. All these processes are simulated by a series of multiphysical models. The reliability of the modeling is tested by comparison with experiments in the literature, and a parametric analysis is performed, based on the process characteristics such as laser sweep speed, its intensity and shape, polymeric grain size among others. Several recommendations to optimize the process are proposed. 1. INTRODUCTION Additive manufacturing of materials is a fast-developing field. Recent major advances in this area are very noteworthy. But, several underlying phenomena are still not well understood to properly model the process and propose process improvements leading to the manufacturing of better quality parts. The SLS process fabricates solid objects by means of laser radiation, which depends on several parameters related to the laser beam: laser power, scanning velocity and wavelength. The laser energy input is often assumed as a heat flux with Gaussian density distribution when computing the temperature field. Recently, several researchers developed models of heat diffusion for laser sintering process. However, they underestimate the effect of the air between grains in the laser sintering process. In fact, the powder bed is always treated as a homogeneous medium instead of discrete granular system an assembly of many discrete solid particles interacting with each other due to dissipative collisions. The Selective Laser Sintering (SLS) or selective laser melting (SLM) is one of the most promising additive manufacturing techniques for modern material processes. Although, the SLS (SLM) process for thermoplastics currently finds many industrial applications, it still leaves quite a lot to be desired concerning the quality of manufactured parts. Comprehensive modelling of the complex physics underlying the process is a real challenge that if met may lead to process optimization and better quality manufactured parts. Several rather simplified theoretical models have been proposed in the literature. Most of the contributions relate to thermal models, simplified thermomechanical modeling and laser-powder interaction at both powder and part scales in [1], with empirical Arrhenius evolution for the material properties in [2]. Berzins et al. [3] investigate the final microstructure of amorphous polycarbonate by a 2D numerical approach. The powder densification and shrinkage based on the empirical Arrhenius evolution proposed in [2] are included in the analysis. Riedlbauer et al. [4] proposed a modeling of the process with some experimental comparison and data. Due to the lack of