Effect of Scanning Velocity on Bending Deformation per Pulse in Sheet Metal Bending by Laser Peen Forming

Laser peen forming is a die-less incremental sheet forming method using laser-induced shock waves. The author had applied femtosecond and sub-nanosecond laser peen forming to sheet metal bending. Changing the coverage is a simple method of controlling bending deformation in the process. However, bending deformation per pulse (bending efficiency), which is high and constant at a high scanning velocity, decreases markedly at a low scanning velocity despite a constant coverage. These findings suggest that bending deformation cannot be controlled by changing the coverage only, and a scanning strategy is another important factor for bending deformation. To clarify the mechanism of such behaviors, the author applied nanosecond green laser peen forming to sheet metal bending and compared the effects of scanning strategies. The tendencies of efficiency decrease were common among three lasers. In addition, when the efficiency decreased, similar relationships between scanning velocity and spot diameter were observed for three lasers. However, when the thickness of the workpiece became larger than the depth of the plastic deformation zone, the decrease in efficiency became unclear.