Three-dimensional kinetic theory approach for laser pulse heating

Abstract

Lasers are widely used as a machine tool in the metal industry. One of the important areas of laser application is surface treatment of engineering metals. To improve the process parameters in the laser heating process, an exploration of the heating mechanism is fruitful. The present study is carried out to develop a three-dimensional model for a laser pulsed heating process using the electron kinetic theory approach. The heating model introduced relies on successive electronphonon collisions; therefore, it is this process that describes the heat conduction mechanism. This study is limited to heat conduction only. Consequently, the phase change process is not taken into account. To validate the theoretical predictions, an experiment is conducted to measure the surface temperature using an optical method. Moreover, a one-dimensional heating model developed previously is also considered and the predictions of three- and one-dimensional heating models as well as experimental results are compared. It is found that the three-dimensional model gives lower surface temperatures compared with the one-dimensional model considered. However, experimental results agree well with the results obtained from the three-dimensional model. In addition, an equilibrium time is introduced. In that case, energy gain of electrons via incident beam absorption balances the energy losses due to conduction through successive electron-phonon collisions.