Laser deep penetration welding simulation based on a wavelength dependent absorption model

Abstract Today laser sources for laser material processing are available at different wavelengths. In this paper it is depicted that the wavelength dependent Fresnel absorption of the laser at the keyhole front is responsible for a different propagation and amplification or attenuation of instabilities at the keyhole front and the keyhole dynamics. To understand the physics of laser deep penetration welding and the interaction of the melt pool dynamics with these instabilities a three dimensional transient simulation of laser keyhole welding process has been developed. The results obtained by this simulation help to understand the different aspects of the formation of instabilities in the keyhole front at different wavelengths. To investigate the implication of the wavelength dependent absorption effects a CO2-laser and an Yb:YAG-laser are simulated. The presented model includes the calculation of the heat flux in the solid and molten phase and a temperature dependent melting and solidification model. The 3D velocity field inside the melt pool and the keyhole is calculated. The free surface of the melt pool is modelled using the Volume of Fluid method.