Laser Heating and the Phase Change Process

Laser-controlled melting finds wide application in industry because of nonmechanical contact between the workpiece and the treated surface, precision of operation, local treatment, and low cost. Although the phase change process has been examined previously, the model studies need further development for an improved understanding of the physical processes involved in the melting process. Analytical treatment of laser-induced melting provides a relation between the melt characteristics, such as the recession velocity of the surface and the melt depth, and the laser parameters. However, the mathematical problems encountered during the model study require one to make a considerable number of assumptions in the analysis to achieve closed-form solutions to the temperature field. Although some of these assumptions are important and useful, they limit physical insight into the melting process. Numerical treatment of the melting process improves the limitations inherent in the analytical approaches; however, it requires considerable computational efforts to simulate the phase change process resembling the actual laser treatment process. Although numerical solution of the phase change problem provides accurate information about the phase change, the analytical approaches complement the numerical predictions. This is due to the fact that the analytical approaches result in extensive information on the phase change process. Therefore, in this chapter, the phase change process, including melting and evaporation, is presented, and the analytical and numerical solutions to the heating problem are given. The steady and transient heating analyses pertinent to laser heating of a one-dimensional semi-infinite body and a two-dimensional plate are presented analytically. The numerical study is introduced to account for the effect of the moving solid body and the laser pulse parameters on the temperature field during a laser-induced phase change process.