High-fidelity modeling of keyhole dynamics during laser melting of metals using interface-conformal meshes
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Laser melting of metals is an important process integral to both laser welding and additive manufacturing technologies. The process physics is a complex combination of radiative absorption, phase change, fluid flow, moving boundaries, surface tension, and vaporization, typically driving the formation of a keyhole, or cavity, beneath the laser. This work presents a high-fidelity modeling approach intended to predict the behavior of laser-induced keyholing. A ray tracing approach with a Fresnel model is used to predict laser absorption by a workpiece. A level set method tracks the location of the moving interface, and a dynamic meshing scheme is used to continually conform the mesh to the interface location. A simplified momentum and energy flux model derived from vaporization mechanics is used to model the recoil pressure of the vaporized metal. Model results are compared to time-resolved effective absorptivity and melt pool geometry data for 316L stainless steel, Ti64, and 5182 aluminum collected using an integrating sphere, X-ray radiography, and inline coherent imaging. Model discrepancies and uncertainties are discussed as well as outstanding challenges to predictive capability
