Modeling and simulation on long pulse laser drilling processing

Combining the modified level-set method a 2D model is developed to simulate the laser drilling process on aluminum slab with millisecond pulsed laser. By utilizing equivalent specific heat capacity and adding source terms of gas dynamics, phase transition is modeled. Modified level-set method is developed in order to trace the liquid-gas interface as well as consider mass loss during evaporation and boiling. The possible effects which can impact the dynamic behavior of the keyhole are taken into account, containing gravity, recoil pressure of the metallic vapor, surface tension, and Marangoni effect. Based on such model the impacts of laser fluence and pulse duration on keyhole width and depth, average drilling velocity, morphology and quality, melt ejection mode transition as well as velocity of melt ejecta are investigated. Compared with some corresponding experiment results, the validity of the established model is verified and the mechanisms of phenomena during laser drilling are analyzed. (C) 2014 Elsevier Ltd. All rights reserved.