| dc.description.abstract | The purpose of this study is to investigate the temperature distribution of powder beds during selective laser sintering or melting by using Discrete Element Method (DEM). The model of heat transfer for granular assemble was developed that consider phase change and temperature-dependent thermal physical properties of the materials. The benchmark tests were established to verify the proposed model of heat transfer. The effects of particle size and scanning pattern on the temperature distributions in the powder bed were explored. Numerical results show that during the laser scanning process, the rise of temperature in the powder beds is mainly caused by laser energy input, not by the heat transfer mechanism. Based on the same processing parameters, such as laser power, scanning speed, spot size, hatch space and scanning pattern, the average temperature in the surface of the powder bed increases linearly with the scanning time, and the powder beds with smaller particles exhibit higher temperature as well as more uniform temperature distribution. The temperature for the short track is slightly higher than that for the long track. The short track results in a more concentrated high-temperature area, while the long track results in a wider temperature distribution. Moreover, at the initial scanning stage of the laser heating (within the melting point of the materials), considering the temperature-dependent thermal physical properties is required in calculating the temperature field. However, beyond the melting point of the material, the temperature-dependent thermal physical properties takes a little effect, because the phase change dominates the rise of the temperature. | en_US |