THE APPLICABILITY OF THE SEDOV-TAYLOR SCALING DURING MATERIAL REMOVALOF METALS AND OXIDE LAYERS WITH PULSED CO2 AND EXCIMER-LASER RADIATION

For the removal of material with pulsed laser radiation the distance t ravelled by the shock or blast wave and the amount of energy released in the plasma state due to the absorption of laser radiation are deter mined experimentally and theoretically. The distance travelled by the blast wave is detected by schlieren photography, the released energy b y monitoring the transmitted laser radiation during the removal proces s. The theoretical evaluation is performed by numerical simulation usi ng a model incorporating the laser-induced vaporization process and th e dynamics of the plasma state. The results obtained from the experime nts and the model are compared with that of the Sedov-Taylor scaling. The removal of the oxide layer from austenitic steel is investigated w ith CO2 laser radiation produced by a TEA and a high-power CO2 laser d evice. For the TEA laser with fluences of 5 and 10 J cm(-2) 50-80% of the pulse energy is released into the plasma state and the Sedov-Taylo r scaling describes the distance travelled by the blast wave in agreem ent with data from the experiments and the simulation. For the high-po wer CO2 laser with a fluence of 50 J cm(-2), 6% of the pulse energy is released into the plasma state and the Sedov-Taylor scaling does not describe the data of the simulation. The process of removal of copper and aluminium material is simulated for excimer laser radiation with f luences of 15 and 30 J cm(-2). For copper 15-30% of the pulse energy i s released into the plasma state and the Sedov-Taylor scaling is appli cable. For aluminium, less than 2% of the pulse energy is released int o the plasma state and the Sedov-Taylor scaling is only applicable for the higher fluence.