Analytical model of the absorptance in full- and partial-penetration laser welding

The investigation, description, and modeling of laser material processing requires knowledge of the power introduced into the workpiece and thus of the absorptance. Analytical expressions are derived for the calculation of the absorptance in a full-penetration welding keyhole that is opened at its top and bottom. The formulas can easily be adapted to also consider partial-penetration welding in which the keyhole is closed on the bottom. The absorptance is calculated as a function of the keyhole geometry, the Rayleigh length of the incident laser beam and the absorptivity of the welded material. Additionally, the absorptance during partial- and full-penetration welding of aluminum was determined experimentally by calorimetric measurements. The proposed model agrees well with the experimental results.