フェムト秒レーザによるレーザピーンフォーミング: 薄板曲げ加工での照射条件と予備曲げの影響

摘要

フェムト秒レーザはそのパルス幅がフェムト秒（1fs=10~(-15)s）rn単位と極めて短く，パルスのピーク出力がギガワット単位と非rn常に大きいことを特徴とする超短パルスレーザである．このよrnうなパルス特性ゆえに熱影響の極めて小さい除去加工や透明体rnの加工などが可能である．%A femtosecond laser is a type of ultrashort pulse laser. A focused femtosecond laser pulse induces high-pressure plasma and a shock wave at the surface of a target. In some cases, this shock wave is enough to deform the target plastically. Laser peen forming is a type of sheet metal forming using this deformation by shock wave. The authors adopted laser peen forming for thin-sheet-metal bending. A piece of sheet metal was bent by femtosecond laser scanning. An investigation was conducted into the influences of irradiation conditions and prebending on forming properties. When irradiating in air, bending angles increased with fluence. However, when irradiating in water, the exceedingly large fluence decreased the bending angles. The bending angles were increased by applying prebending during the irradiation. Selection of appropriate prebending directions and irradiation conditions allowed the bending direction to be controlled. Several pieces of sheet metal for springs were bent into various shapes that would be difficult to achieve using the usual press forming process.