Abstract
This paper presents a quasi-steady stagnation flow analysis for keyhole initiation processes in high intensity laser materials processing, such as laser drilling. The governing stagnation flow equations are normalized, and the important problem parameters are identified. The simple model accounts for conduction in the solid, conduction and convection in the melt layer, and the latent heats of melting and vaporization. The stagnation flow governing equations and boundary conditions are appropriately normalized and solved, and the important combinations of material properties and independent laser parameters are identified. This semi-quantitative analysis yields quasi-steady estimates for the penetration velocity, the thickness of the melt layer, the velocity profiles in the melt layer, and the fraction of melt that is vaporized for varying absorbed laser power and beam radii. Results from inviscid stagnation flow analyses are shown and compared for four different materials: aluminum, low carbon steel, stainless steel, and titanium.
