An Adaptive Discrete Element Method for Physical Modeling of the Selective Laser Sintering Process

摘要

Additive Manufacturing (AM) has recently risen to the forefront of research and development of manufacturing industries as it provides engineers with unique capabilities that are completely unheard of in subtractive manufacturing systems. Properties such as the fabrication of complex, otherwise not-manufacturable, structures and non-expensive low-volume fabrication have helped additive manufacturing to climb the popularity ladder in such a way that it is sometimes even referred to as "The third industrial revolution". The main distinction between AM and subtractive manufacturing technologies (milling, etc.) is that instead of cutting material from a solid block, AM systems fabricate the end-use products directly in an additive, layer-wise fashion.;Selective Laser Sintering (SLS) is categorized as a Powder Bed Fusion (PBF) process. PBF processes are a distinct class of AM systems that use powders as their raw material and use a laser/electron beam to fuse the powders together and fabricate the final product. Powdered metals and ceramics are two of the major raw materials used in PBF processes, resulting in a high demand for industry-scale PBF machines. Therefore, characterization of these processes is a research topic worth exploring.;This dissertation presents a comprehensive approach for addressing the ongoing issues in the field of physical modeling of powder bed fusion additive manufacturing processes. In this work, an adaptive discrete element method is proposed for thermo-mechanical simulation of powdered material during the selective laser sintering process. By adding adaptive refinement to the conventional particle level discrete element model, the developed model gets equipped with the capability of improving the simulation speed while maintaining the computational accuracy of the conventional DEM. Empirical models for fusion of powder particle under the influence of the laser beam is also included in the simulation. Moreover, a homogenization technique based on the results of the developed thermo-mechanical method is presented that has the potential of calculating the elastic properties of SLS products. The developed models have been validated, showing that their results follow the expected trends.;This dissertation is an effort in creating a much needed physical modeling tool for complete virtual manufacturing and testing of SLS products. Further development of this idea could significantly increase the impact of AM technologies in a wide range of industrial applications.