Plume Heat Transfer in Laser Processing of Materials

这项研究是对热的机制的调查 与羽流形成有关的转移， 激光辐射与金属靶的相互作用。 的 研究的主要目的是发展 可用于确定相对 羽流吸收、散射和排放对 将激光能量耦合到金属靶中。 使用的方法 包括高速摄影、目标温度 测量、羽流光散射和透射 测量和校准的羽流发射光谱。 一 脉冲Nd-YAG激光器被用作入射的主要源 在105 W/cm 2和更大的通量水平下的激光辐射。 铝和铝合金材料被用作靶。 本研究的另一个目的是调查 辅助气体对羽流电离和耦合的作用 激光能量进入工件。 分子的影响 氧对羽流电离度的研究， 在不同的大气中进行测试， 氧气 这项研究的意义在于， 了解与之相关的传热机制， 预计会形成羽流。 本研究将 帮助实现这项研究计划的长期目标 它提供了对热传递的理解 激光靶相互作用的机制，使激光可以 充分利用其在材料加工中的优势。

This study is an investigation of the mechanisms of heat transfer associated with plume formation occurring during the interaction of laser radiation with metal targets. The primary objective of the study is the development of techniques which can be used to determine the relative importance of plume absorption, scattering, and emission on coupling of laser energy into metal targets. The methods used include high speed photography, target temperature measurement, plume light scattering and transmission measurements, and calibrated plume emission spectroscopy. A pulsed Nd-YAG laser is used as the primary source of incident laser radiation at flux levels of 105 W/cm2 and greater. Aluminum and aluminum alloy materials are used as targets. Another objective of this study is the investigation of the role of the assist gas on plume ionization and coupling of laser energy into the workpiece. The influence of molecular oxygen on degree of plume ionization is studied by performing tests in various atmospheres with and without molecular oxygen. The significance of this study is that a clearer understanding of the heat transfer mechanisms associated with plume formation is expected to be obtained. This study will help accomplish the long term goal of this research program which is to provide an understanding of heat transfer mechanisms in laser target interaction so that lasers may be utilized to their full advantage in materials processing.