2-DIMENSIONAL MODEL FOR MATERIAL DAMAGE DUE TO MELTING AND VAPORIZATION DURING LASER IRRADIATION

A two-dimensional model is developed for material damage caused by melting and vaporization during pulsed laser irradiation. The problem is formulated by using the energy conservation equation (the Stefan condition) at various points on the solid-liquid and liquid-vapor interfaces. The effect of curvature of the solid-liquid and liquid-vapor interfaces are taken into account and the problem is solved numerically by using the Runge-Kutta method. For determining the maximum damage that can occur during laser irradiation, the laser energy is considered to be utilized only to melt and vaporize the material. The effect of various laser parameters, such as the laser power, laser beam diameter, pulse-on time, and the number of pulses per second on the depth and the radius of the crater is presented. Also, the tapering angle of the crater and the formation of recast layer in the crater during laser irradiation are examined in this study. Finally, a linear relationship between the maximum crater depth and the "gross" laser intensity is derived phenomenologically and verified by using the numerical results of this study.