A Stagnation Flow Analysis of the Heat Transfer and Fluid Flow Phenomena in Laser Drilling

Abstract

This paper presents a quasi-steady stagnation flow analysis for the material removal processes in high-intensity laser materials processing, such as laser drilling. The governing stagnation flow equations for the heat transfer and fluid flow phenomena are derived for the region near the centerline of the laser beam. The analysis 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 semiquantitative analysis yields quasi-steady estimates for the penetration velocity, the thickness of the melt layer, the velocity and temperature profiles in the melt layer, and the fraction of melt that is vaporized for varying absorbed laser power and beam radius. Inviscid results from the stagnation flow analysis are shown for five different materials: aluminum, copper, low carbon steel, stainless steel, and titanium. Relatively good agreement exists between the results from the analysis and experimental data from the literature. [S0022-1481(00)01804-1]