Modeling of Laser-matter Interaction Applied to Laser Welding with COMSOL Multiphysics®

Keywords

Laser-matter interaction, electromagnetism, Maxwell equations, heat transfer, analytical model

Context / Goal

In many industrial processes for example drilling, cutting or welding, a laser heat source is used to reach very high densities of energy (~ MW/cm²) and local melting of materials. The laser-matter interaction and the amount of energy applied on the surface are linked to the media absorptivity, the incidence angle of the laser beam or the geometry of the cavity.

The client wants to obtain the spatial distribution of the energy density as a function of time and the resulting temperature field, in order to improve the efficiency of the process.
 

SIMTEC's Achievements / Results

A modeling strategy has been established with the client and SIMTEC. Two types of approaches have been developed to model the problem of the laser heat source with COMSOL Multiphysics®:
 

  • Analytical model

The first approach is based on an analytic model that determines an equivalent absorptivity as a function of the opening surface and an opening angle as well as the total surface .

This approach is used to give a first order of magnitude of the power applied on the surface. The multiple reflections of the beam inside the cavity are considered globally. However, it is only valid for regular topology of cavities.
 

  • Electromagnetic model

In order to model more precisely and locally the energy density at the surface, the specific behavior of a laser wave is solved by MAXWELL equations. For a given frequency, the electric field is shown here in the cavity, highlighting the reflections on the walls. The thermal coupling is also taken into account in order to compute the temperature field in the irradiated material and to give local precision to the client:

 

Two numerical approaches have been developed and implemented in the COMSOL Multiphysics® software in collaboration with the client. Depending on the precision level required, the client can now use these two different approaches.