NONLINEAR STABILITY ANALYSIS OF MOLTEN FLOW IN LASER CUTTING

The method of multiple scales is used to investigate,the nonlinear sta bility behavior of a thin molten laser cutting. In this analysis, the balance of momentum and energy with the effects of phase change is con sidered. Under the assumption of long wavelength, a corresponding nonl inear generalized kinematic equation for the film thickness is thereby derived. The result shows that there exist supercritical stability in the linearly unstable region and subcritical instability in the linea rly stable region. For higher cutting speeds, the surface roughness co uld be improved by decreasing the cutting speed or increasing the gas velocity due to the decreasing of the maximum equilibrium finite ampli tude. On the other hand, for lower cutting speeds, the surface roughne ss could be improved by increasing the cutting speed or decreasing the gas velocity due to the increasing of the minimum threshold amplitude .