Evaluation of pulsed QCW laser irradiation on concrete in upward direction

Nguyen, P. L.; 大道 博行; 松永 幸大; 山田 知典; 西村 昭彦  ; 河内 哲哉

Nguyen, P. L.; Daido, Hiroyuki; Matsunaga, Yukihiro; Yamada, Tomonori; Nishimura, Akihiko; Kawachi, Tetsuya

Pulsed laser processing of material which includes laser drilling, welding, cutting, etc. is an important part of the laser technical application. Laser irradiation techniques for removing concrete structure defect in the tunnel of railways is an urgent task for operation and maintenance in the JR West tunnels, Japan. In this work, the experiment has been performed for upward laser drilling and cutting on a tip of concrete. For requirement of small apparatus with high accuracy, the QCW (Quasi continuous wave) fiber laser system having compact dimensions was connected with optical head. Results show that the penetration depth was increased in upward drilling compared with that of downward drilling. Especially at higher peak power, this increase was enhanced due to the assistance of gravity. There exists an optimal percentage of overlapping region, which satisfies the requirement of the effective cut depth and cutting speed. For this experiment, the optimal percentage of overlapping region is achieved about 40-50%. Also, cut depth is a function of scan number in pulsed laser upward cutting concrete.