Numerical simulation and experimentation of micro scale laser bulge forming

Micro scale laser bulge forming is a high strain rate micro-forming technique, which employs the shock wave pressure induced by a laser pulse to deform thin metals to 3D configurations. The process holds promise for fast setup, well-controlled, high efficiency and precision of fabrication of complex miniaturized devices. In this paper, micro scale laser bulge forming of pure copper was investigated using both numerical and experimental methods. A finite element model was proposed to simulate the dynamic deformation of the shocked material, and the simulation results were validated by experiments. With the verified model, the deformation mechanism of the transient forming process was characterized through the evolution of equivalent plastic strain rate and the distributions of strains and residual stresses. In addition, the effects of laser energy, die diameter and sample thickness on the forming behavior of copper foils were studied. The experimental and numerical simulation results show that with an increase of sample thickness, the deformation depth decreases, while it becomes larger as the enhancement of laser energy. The shock forming process is not very sensitive to the diameter of the die, indicating that it is feasible for micro products in a wide dimension range.