Material response to laser pulse heating: A kinetic theory approach

Lasers find wide applications in industry due to their precision operation and low cost. Laser machining processes exhibit common characteristics such as heating, melting and evaporation. Modelling of the heating process may enhance understanding of the laser machining process, which in turn minimizes the optimization cost. This study is conducted to explore the laser heating process including evaporation through the electron-kinetic theory approach. The basis in examining the problem using the kinetic theory approach is to describe the transport of energy through electron-phonon and molecule-phonon collisions. A numerical scheme is introduced to solve the resulting coupled-energy equations, since the governing equations are in the form of integro-differential equations. To obtain the material response to the heating pulse, three different heating pulses are employed, consequently, the resulting temperature distributions inside and at the surface of the substances are computed. The study is extended to include first and second law efficiencies of the melting process, which in turn provides the pulse shape giving the improved melting efficiency. It is found that the temperature distribution in the vicinity of the surface depends on the electron distribution and number of collisions taking place in this region. The Fourier theory results, obtained from the previous study, gives a lower surface temperature than that predicted from this study.