Laser pulse heating and flexural wave generation during treatment of metallic surfaces

Non-conduction limited laser heating of metallic surfaces results in evaporation of the surface. This, in turn, generates a recoil pressure across the interface between the melted and evaporated zones. Depending upon the magnitude of the recoil pressure, a pressure force normal to the workpiece surface is resulted. This causes the generation of flexural waves. In the present study, closed form solution for surface temperature rise during a laser heating pulse is presented and resulting recoil pressure is formulated using a momentum balance across the vapor-liquid interface at the workpiece surface. The flexural wave analysis due to pressure force is carried out for different workpiece geometric configurations. It is found that the peak value of the recoil pressure predicted agrees well with the previous findings and the flexural wave with amplitude of 20 μm at the workpiece center is generated. Moreover, the frequency and amplitude of flexural wave vary with workpiece geometric configuration; in this case, both ends fixed workpiece results in fast rate of damping of flexural wave amplitude.