Prediction of hole characteristics and hole productivity during pulsed Nd:YAG laser beam percussion drilling

A thermal finite element model is proposed to simulate and predict hole taper (T-sigma), heat-affected zone and material removal rate during laser beam percussion drilling in two difficult-to-laser-drill materials having wide difference in their thermophysical and optical properties. The developed model incorporates temperature-dependent thermal properties, optical properties and phase change phenomena of the sheet materials to predict the hole profile through the isotherm generated along the depth of the hole due to repeated laser pulses. Hole characteristics and hole productivity parameters are compared for both the sheet materials. The predicted values of hole taper with respect to pulse width have been compared with the experimentally obtained values. It is observed that hole characteristics are mainly affected by pulse width in the Aluminium alloy sheet and pulse frequency in the Inconel sheet, whereas peak power has prominent effect on material removal rate for both the sheet materials.