サブナノ秒マイクロチップレーザーによるレーザーピーンフォーミングの変形特性

抄録

A high-power pulsed microchip laser, which has a pulse duration of sub-nanosecond order, had been developed. A focused microchip laser pulse can induce an effective shock wave for deforming the irradiated metal surface plastically. When a sheet metal surface is scanned by the laser, dieless sheet forming, called laser peen forming, is achieved through the accumulation of such plastic deformations. The authors have applied the method to sheet metal bending. A tamping layer, such as water, on a target surface encourages laser-induced shock waves. Therefore, the sheet metals were irradiated in water. Several materials were bent, and the feasibility of the process was confirmed. Fundamental deformation properties in terms of forming parameters, such as defocusing, pulse energy, material hardness, and thickness, were examined. It was confirmed that, qualitatively, the process had similar deformation modes to those obtained by peen forming. However, when fluence was greatly increased by focusing or increasing the pulse energy, laser absorption by water reduced the bending deformation.