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Beam-Material Interactions and Dynamic Processing Characteristics in Laser Micro-thermal Materials Processing

激光微热材料加工中的光束-材料相互作用和动态加工特性

基本信息

批准号：
61460209
负责人：
MATSUNAWA Akira
金额：
$ 3.78万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

Beam-material interactions and dynamic processing phenomena during a pulsed YAG laser materials processing have been clarified by various optical measurements and pulse chopper method. Main conclusions obtained in this study are summarized as follows:1) A bright flame, so called the laser induced plume or plasma, which generates at the pulse laser irradiation on a target is proved to be not a plasma but a low temperature and high density vapor jet of tarfet atoms. The light emission from plume takes place only at the early stage of laser pulse duration and the plume is in the unexcited state for most of the gation. Scattering loss of incident beam by ultra-fine particles becomes dominant after the decay of light emission.2) When the irradiation power density at the target surface is moderate, the plume is a laminar jet which is consisted of double layers, i.e., inner core of evaporated atoms and outer sheath layer of compressed ambient gas. while, When the power density becomes higher, the plume turns into a highly terbulennt subsonic jet and a fine thread of liguid is emerged from the target which beraks into fine particles as spattering.3) Temporal change of fusion zone of target has been clatified by high speed photographic study as well as pulse chopper method. At the time of laminar plume generation, the molten pool surface is fairly flat and the penetration develops mainly by the heeat conduction. On the other hand, when a terbulent plume is generated, the molten pool is deeply depressed by the recoil pressure of plume and the laser power is directly given to the exposed fudion boundary which leads very quick developmint of penetration.

通过各种光学测量和脉冲斩波方法，阐明了脉冲激光材料加工过程中的光束-材料相互作用和动态加工现象。主要结论如下：1)脉冲激光照射靶材时产生的明亮火焰，即激光诱导的羽流或等离子体，不是等离子体，而是一种低温、高密度的焦油原子蒸汽喷流。羽流的光发射只发生在激光脉冲宽度的早期阶段，在大部分时间内羽流处于非激发状态。2)当靶表面的辐照功率密度适中时，羽流是由蒸发原子的内核和压缩环境气体的外层组成的双层层流射流。而当功率密度增大时，羽流转变为亚音速强喷流，并在溅射过程中形成细小的液体细丝。3)利用高速摄影技术和脉冲斩波法研究了靶材熔合区的时间变化。在层流羽流产生时，熔池表面比较平坦，熔池的侵彻以堆芯传导为主。另一方面，当产生激波羽流时，熔池受到羽流反冲压力的强烈抑制，激光能量直接照射到暴露的熔池边界上，使侵彻发展得非常迅速。