  Many additive manufacturing (AM) technologies rely on powder feedstock, which
is fused to form the final part either by melting or by chemical binding with
subsequent sintering. In both cases, process stability and resulting part
quality depend on dynamic interactions between powder particles and a fluid
phase, i.e., molten metal or liquid binder. The present work proposes a
versatile computational modeling framework for simulating such coupled
microfluid-powder dynamics problems involving thermo-capillary flow and
reversible phase transitions. In particular, a liquid and a gas phase are
interacting with a solid phase that consists of a substrate and mobile powder
particles while simultaneously considering temperature-dependent surface
tension and wetting effects. In case of laser-metal interactions, the effect of
rapid evaporation is incorporated through additional mechanical and thermal
interface fluxes. All phase domains are spatially discretized using smoothed
particle hydrodynamics. The method's Lagrangian nature is beneficial in the
context of dynamically changing interface topologies. Special care is taken in
the formulation of phase transitions, which is crucial for the robustness of
the computational scheme. While the underlying model equations are of a very
general nature, the proposed framework is especially suitable for the mesoscale
modeling of various AM processes. To this end, the generality and robustness of
the computational modeling framework is demonstrated by several
application-motivated examples representing the specific AM processes binder
jetting, material jetting, directed energy deposition, and powder bed fusion.
Among others, it is shown how the dynamic impact of droplets in binder jetting
or the evaporation-induced recoil pressure in powder bed fusion leads to powder
motion, distortion of the powder packing structure, and powder particle
ejection.
