Investigation of Obstacles with Interactive Elements on the Flow in SiC Three-Dimensional Printing.

A single screw extruder is used in this study to efficiently transport SiC slurry in direct ink writing (DIW) technology. The deposits caused by low viscosity and the agglomerations resulting from the nonuniform mixing form the obstacles in the channel, which affect the normal flow of the slurry, theoretical outlet velocity, and interaction with other printing parameters. Therefore, it is necessary to study the effect mechanism of the obstacles on the flow. The obstacles are always irregular, which makes it difficult to directly analyze them. Irregular geometries are always composed of linear and/or arcuate elements; therefore, the obstacles can be simplified into regular geometries. In the present work, interactive elements, including line-line, line-arc, arc-arc situations are analyzed. Then, an improved multiple relaxation time lattice Boltzmann method (MRT LBM) with a pseudo external force is proposed for the flow analysis. The improved MRT LBM is combined with rheological test data to investigate cases with interactive elements, and the results are applied to reveal the general mechanism. The results show that the positions are common influencing factors, which affect the streamlines, outflow directions, and outlet velocity distributions. In addition, in different situations, different factors are considered to affect SiC slurry flow. It is obvious that the existed obstacles inevitably change the theoretical flow direction and outlet velocity, which has a synergistic effect on the printing parameters. It is necessary to understand the effect mechanism of the obstacles on the flow.