Surface Topography Control of TA2 Pure Titanium in Laser Shock Peening

Laser shock peening (LSP) induces an irregular topography on the treated metal surface, thereby reducing the gain effect of the metal fatigue property caused by compressive residual stress. A technique named laser shock imprinting (LSI) is proposed in this paper to guide plastic deformation on a titanium surface. An FEM simulation and experiment were conducted to explore the embossment forming process and residual stress distribution of TA2 pure titanium. The simulated results show that the embossment on the sample surface went through five stages, namely, static, growth, rebound, fluctuation and stabilization, under a single LSI. With an increase in loading pressure, the contact pressure between the sample and contact foil increased along with increasing embossment height. Sufficient loading pressure could induce a difference in residual stress between the zones with and without embossment. The experimental results show that the height and clarity of embossment increased with increasing laser energy, a result similar to that of the simulation. In addition, compared with LSP, the sample treated by LSI had a lower surface roughness and flatter surface profile.