Determination of High-Temperature Properties Relevant to Laser Materials Processing

虽然激光加工（钻孔、切割、焊接）正在以极快的速度获得工业重要性，但其基本过程仍然知之甚少，这主要是因为缺乏对高温特性数据的了解（被加工的材料，以及在其上方形成的激光羽流）。如果没有这些属性数据，现有的复杂模型可以准确地预测钻井速率、孔径、锥度、切削速率等。本研究主要针对三组实验，测量CO2和Nd:YAG激光加工陶瓷的所有相关高温特性：(1)在积分球装置中测量几种陶瓷样品的吸收率（在激光波长下，作为温度的函数）、烧蚀温度和烧蚀材料所需的能量。(2)通过高速摄影和红外测温对激光相互作用区进行成像，捕捉去除机制（烧蚀、分解、熔化或微爆去除），识别碎片去除和再沉积。(3)激光羽流的吸收系数将在激光波长（以确定光束阻塞的量）和中红外（以确定羽流的再发射）使用透射和发射光谱测量。这项研究的结果将允许对陶瓷的激光加工进行定量预测，并将为测量其他材料（包括金属）的相关特性提供实验设计。

ABSTRACT -- CTS-9312325 PI -- Michael F. Modest While laser processing (drilling, cutting, welding) is gaining industrial importance at an extremely rapid pace, the basic process remains poorly understood, largely because of a dearth of knowledge of high-temperature property data (of the material being processed, and of the laser plume forming above it). Sophisticated models exist that could accurately predict drilling rates, hole diameter, taper, cutting rates, etc., were it not for this lack of property data. This proposal addresses three groups of experiments, which will be carried out to measure all relevant high-temperature properties for CO2 and Nd:YAG laser processing of ceramics: (1) The absorptivity of several ceramic specimens (at the laser wavelengths, as a function of temperature), the ablation temperature, and the energy required to ablate material will be measured in an integrating sphere apparatus. (2) The laser interaction zone will be imaged through high-speed photography and infrared thermometry to capture the removal mechanism (ablation, decomposition, melting, or micro-explosive removal) and to identify debris removal and redeposition. (3) Absorption coefficients of the laser plume will be measured at the laser wavelengths (to determine amount of beam blockage) and in the mid-infrared (to determine re-emission from the plume) using transmission and emission spectroscopy. Results from this investigation will allow quantitative predictions for laser processing of ceramics, and will provide experimental designs to measure the relevant properties for other materials, including metals.