Soutenance de thèse : Lan ZHANG

Modelling of additive manufacturing processes: case of polymer laser sintering

Doctorante :  Lan ZHANG

Laboratoire INSA : CETHIL

Ecole doctorale : ED162 : Mécanique, Energétique, Génie Civil, Acoustique de Lyon

The selective laser sintering (SLS) process is a promising addictive manufacturing technique. This thesis is to develop a computational tool capable of accurately describing heat transfer in a SLS process. The laser transmission in the polymer particles and the polymer physical properties alteration during the SLS process are investigated through numerical models. The involved phenomena including the laser-powder interaction, coalescence, powder bed's densification, melting, and crystallization are all addressed by different simulation models. Scattering as an important phenomenon needs to be considered in the laser-powder interaction model. The modified Monte-Carlo method and Mie-Scattering theory are used to model the laser photons-powder bed interaction and heat transfer in a powder bed. Then, the thermal history of a typical SLS process (time evolution of temperature) is obtained by numerical simulation. In order to qualify the influence of scattering on the SLS process, time-evolution of surface temperature is recorded by an IR camera and sample dimensions are measured. The comparison between numerical results and experimental data of temperature time-evolution indicates that using scattering model predicts better temperature distribution on the powder bed surface. In terms of sample's dimensions, the comparison between measurement and simulation also shows the advantages of the scattering model. The part's final properties, including the geometric dimension, polymer crystallinity, and porosity are predicted based on our computational tool, and compared with measurements, the comparison reveals the reliability and usefulness of our model.