Numerical simulation of hole profile in high beam intensity laser drilling

Abstract

Hole drilling with high intensity (> 108 W/cm2), short laser pulses (several hundred nanoseconds or shorter) has attracted considerable new interests in industrial applications. The emergence of high average power (kilowatt level), Q-switched, diode-pumped industrial solid state lasers has made it practical to implement these superior laser parameters for improved quality and productivity in machining operations in a wide range of industries including aircraft engines, airframe, power generation, and automotive.To understand the basics of this process, a model for evaporation-dominated metal drilling with high intensity short laser pulses is developed. The results of numerical simulation of hole profiles for drilling with high incidence angles are presented and compared with experimental results. Calculations show that material removal due to reabsorption of the laser beam reflected from the side walls of the hole becomes dominant when the hole depth increases. Thus, calculation of absorbed laser intensity requires consideration of multiple reflections and reabsorption. The effect of the beam incidence angle, the absorption coefficient of the material, and the beam intensity on the hole profile is analyzed. The new insights will help us determine the fundamental mechanisms and optimize process parameters for specific drilling applications.Hole drilling with high intensity (> 108 W/cm2), short laser pulses (several hundred nanoseconds or shorter) has attracted considerable new interests in industrial applications. The emergence of high average power (kilowatt level), Q-switched, diode-pumped industrial solid state lasers has made it practical to implement these superior laser parameters for improved quality and productivity in machining operations in a wide range of industries including aircraft engines, airframe, power generation, and automotive.To understand the basics of this process, a model for evaporation-dominated metal drilling with high intensity short laser pulses is developed. The results of numerical simulation of hole profiles for drilling with high incidence angles are presented and compared with experimental results. Calculations show that material removal due to reabsorption of the laser beam reflected from the side walls of the hole becomes dominant when the hole depth increases. Thus, calculation of absorbed laser intensit...