Nano-second laser pulse heating and assisting gas jet considerations

The nano-second laser pulse gas assisting processing method offers considerable advantages in the heat treatment process. In the present study gas assisted nano-second pulse laser heating of a stationary surface is considered. The gas, which is air, impinging onto the workpiece surface is modelled using flow equations, while the low Reynolds number k– ϵ model is employed to account for the turbulence. A heat conduction equation is introduced for the solid heating. A numerical scheme using a control volume approach is employed when discretizing the governing equations. The simulation is repeated for two gas jet velocities. To validate the present predictions, an analytical solution accommodating the convection losses is introduced for the workpiece heating. It is found that the temperature profiles predicted from the simulations agree well with the analytical solutions. Moreover, impinging gas jet velocity has no significant effect on the temperature distribution in the workpiece. As the heating progresses, the equilibrium heating initiates, in which case the internal energy gain of the solid increases at an almost constant rate.