Modified enthalpy method applied to rapid melting and solidification

The rapid melting and solidification of a target material was studied. The enthalpy technique was used in an explicit finite difference form to calculate the location of the solid-liquid interface and the temperature distribution in the target. The technique was modified so that it is not necessary that the temperature of the mesh containing the interface remain constant at the melting point. Instead, by using the energy boundary condition at the interface a new value of the temperature of the grid point is calculated at every time step. The materials between two grid points that are on each side of the interface consist of two phases with considerably different thermal conductivities. The thermal resistances of the material between these grid points were calculated by treating the region as a composite material. The effects of the duration, the temporal shape and the intensity of the laser pulse on the rate of propagation of the phase change and on the temperature distribution were studied. The results of the numerical prediction for the melt depth created in an aluminum target with a 100 ms electron beam were compared with experimental data and good agreement was obtained.