Product Code: ICA12_204

Simulation of the Laser Drilling Process with the Constraint Natural Element Method
Authors:
Jeremie Girardot, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
L. Illoul, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Philippe Lorong, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Nicolas Ranc, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Matthieu Schneider, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Laurent Berthe, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Veronique Favier, PIMM Laboratory (CNRS), Arts et Metiers ParisTech; Paris France
Presented at ICALEO 2012

The simulation of a machining process such as the laser drilling in a percussion regime is very useful to predict the hole morphologies and the induced defects in the drilling system. It also helps the understanding of phenomena occurring during the laser drilling. For power density ranging from 10 to 50 MW/cm², the main physical interaction between laser and material to be drilled involves heating the surface of the material up to the vapor point by focusing the laser beam. The melt part is ejected by the vapor pressure and thus, a part of the matter is removed. These phenomena keep going throughout the material thickness until there is a complete hole. It results from thermal exchanges between the laser beam, the melted part which is ejected and the solid that have to be accounted for properly modeling the process.
Several simulations of the laser drilling were proposed by using a finite element method coupled either with a "front capturing" method (as the level set method) or with a "front tracking" method (as the ALE method). These numerical choices are restricted to the finite element method itself, especially because of the presence of a mesh.
This work presents a new numerical approach using the Constraint Natural Element Method (CNEM), a method close to the meshless methods. The CNEM allows us to handle, in a simple way, the geometric evolution of the interfaces between liquid/solid and liquid/gas and facilitates the numerical implementation of the Heat equation and the Navier-Stokes equations. The multiphysical coupling induced by the vaporization is also taken into account.