Discrete Element Method Modeling of Laser Beam Absorption on Rough Surfaces and Powder Beds

Abstract

The energy transfer from a laser beam source to material surfaces with arbitrary geometrical features and variable surface roughness is the crucial step in many high-end engineering applications. We present a high-fidelity numerical framework for the simulation of laser beam interaction with such surfaces, which include meshed geometry of arbitrary shape and material Lagrangian particles. The method discretizes the laser source as a collection of photon-type immaterial Lagrangian particles and is able to capture the effects of multiple reflections, angle-dependent reflectivity, and polarization change. Validation is conducted against the experimental measurement of the effective reflectivity of a rough copper sample, revealing the impact of the polarization effects. The method is also applied to powder beds and powder layers, and a new theoretical algebraic model for the effective reflectivity of powder layers versus layer sparseness is proposed, based on the simulation data.

Keywords: laser, Discrete Element Method, Rough surface, Powder bed, Ray tracing