NUMERICAL SIMULATION ON RESPONSE OF SHEET METAL SUBJECTED TO LASER SHOCK WITH FINITE DIFFERENCE METHOD

With the action of laser pulse, the deformation velocity of sheet metal is fast, and the propagation of stress wave induced by laser shock wave in material is complex. It is difficult to effectively measure the dynamic responses of sheet metal with traditional measuring tools during the forming process. To solve this problem, theoretical analyses and experiments are used in this paper, a two-dimensional axial symmetric numerical model of sheet metal subjected to laser shock is constructed, the Lagrangian equation of motion is established to obtain its explicit solution with finite difference method, the displacement responses and the propagation of stress wave in the forming process of sheet metal with laser shock are studied, and the effects of different technological parameters on dynamic response characteristics of sheet metal are discussed. The results show that the velocity of sheet metal increases in an oscillatory manner in the initial stage of forming process, an obvious phenomenon of bounce can be observed during the rapid tensile deformation, and the stress wave formed at the edge of laser spot propagates inwards and outwards respectively along the redial. In addition, the dynamic response characteristics of sheet metal very rely on the spatial distribution of pressure pulse and the boundary conditions have considerable effects on final forming results of sheet metal. The results of laser shock experiment are consistent well with the numerical results and the theoretical prediction value. The method and the conclusions in this paper can be utilized to provide a reference for the parameters optimization in the process of laser shock forming.