Laser machining of ceramics: Experimental determination of material properties and simulation of laser-driven plasma.

摘要

As the application of lasers in an industrial setting has gained considerable importance in the past few decades, sophisticated numerical models that deal with laser drilling, scribing and cutting have been developed. However, the quantitative prediction of the basic process remains unsolved, primarily due to a lack of knowledge of relevant material properties. A significant trend of laser development has been the constant push toward higher power and shorter pulses. With increasing irradiance the temperature of the vapor increases and eventually leads to substantial ionization of the gaseous phase. This thesis addresses a research effort that studies the high-temperature properties for CO2 and Nd:YAG laser processing of ceramics and the effects of plasma initiation and expansion during the machining process. The material properties measured include: (1) the absorptance of several ceramic specimens (at the laser wavelength, as a function of temperature) and (2) the energy required to ablate material for a few ceramics. The experimental results can provide reliable property data for numerical models of laser processing. A numerical investigation was also performed to study the plumes generated from a ceramic target during laser operations and their effects on the machining process. The simulation results shed light on laser induced vaporization process and the effects of laser induced plasma on laser machining process.