Self-defocusing of a laser beam in the process of deep penetration welding

摘要

In this contribution, we report on the results of analytical approaches and computer simulations of laser beam self-defocusing in laser induced plasma and gas oncoming flow above a cavity in deep penetration welding at atmospheric conditions. Nonlinear lens-like processes in oncoming jet flow ensure the feedback loop between the evaporation, penetration and laser beam intensity distribution in a workpiece. The processes are self-consistent with the conditions of the stable cavity existence. It is shown that the oncoming hot air jet flow above the plume brings the main contribution in the steady state and instability of the nonlinear beam broadening, which.may reach 300%.