Transient axisymmetric model for laser drilling

A transient axisymmetric model is developed to study the laser drilling phenomenon. Governing equations are the transient axisymmetric 3-D heat conduction equation for the solid substrate and for the liquid molten part, the thin layer model (TLM) equations are utilized. Boundary element method (BEM) is used for the region encompassing the moving boundary and finite difference method (FDM) is utilized for the remainder. BEM and FDM are coupled using flux and temperature at their interface. TLM is obtained using simplified free surface, mass, momentum and energy equations in body intrinsic coordinates. They are simplified by integrating across the layer using profiles for velocity and temperature thus obtaining a 1-D transient hyperbolic system. This is solved by a space-time flux conservation method. The TLM is coupled to the BEM-FDM by the common interface matching conditions. The constitutive equations governing laser interaction with material are used at the liquid-vapor interface.