Modeling keyhole oscillations during laser deep penetration welding at different spatial laser intensity distributions

Process dynamics have a significant effect on the formation of unwanted weld defects like pores in deep penetration laser beam welding. The dynamics of the keyhole, typically evolving in the process, are assumed to be one of the main influencing factors on the welding process. One of the factors influencing the keyhole dynamics is the laser intensity distribution. In order to get a better understanding of the formation of weld defects, the influence of the focal spatial laser intensity distribution on keyhole dynamics is investigated in this work. An analytical description is presented, that offers the possibility to quickly calculate the keyhole dynamics for different spatial laser intensity distributions. Frequency analysis of the calculated keyhole dynamics show that a top hat intensity distribution leads to higher maximum frequencies of the keyhole oscillations compared to a Gaussian beam profile. Experiments using process observation of acoustic emissions confirm the model´s results. © 2014, German Academic Society for Production Engineering (WGP).