Observation of penetration with infrared thermography in laser welding

Abstract
The temperature field in every point of an homogeneous plate submitted to a moving heat source is obtained with a semi analytical method using Green's functions. This method is used to calculate the temperature field on and near the bead in laser welding and results are compared with the measurements obtained on one hand with an infrared thermography device and on the other hand with thermocouples located near the welding seam. The study was made with different plate thicknesses. The simulated and measured temperatures with infrared thermography on the welding bead concur at some distance behind the laser beam. The temperatures depend on the welding parameters and thus on the depth of the welded seam. It is therefore possible to control power and focus conditions in laser welding by infrared surface temperature measurement.