  Laser-based metal processing including welding and three dimensional
printing, involves localized melting of solid or granular raw material, surface
tension-driven melt flow and significant evaporation of melt due to the applied
very high energy densities. The present work proposes a weakly compressible
smoothed particle hydrodynamics formulation for thermo-capillary phase change
problems involving solid, liquid and gaseous phases with special focus on
selective laser melting, an emerging metal additive manufacturing technique.
Evaporation-induced recoil pressure, temperature-dependent surface tension and
wetting forces are considered as mechanical interface fluxes, while a Gaussian
laser beam heat source and evaporation-induced heat losses are considered as
thermal interface fluxes. A novel interface stabilization scheme is proposed,
which is shown to allow for a stable and smooth liquid-gas interface by
effectively damping spurious interface flows as typically occurring in
continuum surface force approaches. Moreover, discretization strategies for the
tangential projection of the temperature gradient, as required for the discrete
Marangoni forces, are critically reviewed. The proposed formulation is deemed
especially suitable for modeling of the melt pool dynamics in metal additive
manufacturing because the full range of relevant interface forces is considered
and the explicit resolution of the atmospheric gas phase enables a consistent
description of pore formation by gas inclusion. The accuracy and robustness of
the individual model and method building blocks is verified by means of several
selected examples in the context of the selective laser melting process.
