| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 97 === The effects of the laser induced plume on the energy absorption and hole-shaping in laser drilling have been investigated numerically and experimentally in this study. In the laser drilling process, the substrate material is heated and vaporized by laser beam and the vaporized matters eject from the substrate surface and form the vapor plume. The plume rises from the substrate surface and nucleates as particles after the vapor temperature is decreased. Furthermore the laser beam will be scattered by the plume particles and the absorption of the laser beam on the substrate will decrease.
In the numerical simulation, the physical models include target heating, plume diffusion, particles nucleation and light scattering. The numerical results show that the increase in laser power density will decrease with the effective drilling time but increase the material removal rate in laser drilling.
In the experiment, the graphite target is drilled by a Nd:YAG pulsed laser with various pulse conditions. Furthermore the beam pulse was observed, the results show that the increase of pulse duration time will increase energy of single pulse but decrease the average laser intensity for the present laser system.
Both the numerical and experimental results show that the averaged material remove rate and averaged drilling rate decreases with the increase of the energy density of laser pulse.
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