圆锥形小孔内等离子体的反韧致辐射吸收研究

Study on Inverse Bremsstrahlung Absorption of Plasma in a Conical Keyhole

在假设小孔为圆锥形的基础上,按照几何光学理论,通过跟踪光线在小孔内的多次反射轨迹,对激光深熔焊接小孔内等离子体的反韧致辐射吸收进行了详细研究.计算了小孔孔壁通过孔内等离子体的反韧致辐射吸收的激光功率密度,分析研究了孔壁的多次反射次数、圆锥形小孔的锥顶角以及圆锥形小孔的直径等因素对孔壁上的激光功率密度分布的影响.通过比较小孔内等离子体的反韧致辐射吸收的激光功率密度和小孔孔壁上的多次反射吸收的激光功率密度,分析了两种能量吸收机制在小孔形成和维持过程中所起的不同作用.

On the assumption of conical keyhole and using geometrical optics theory, a detailed study of the inverse Bremsstrahlung absorption of the plasma in the keyhole in deep penetration laser welding of metals was carried out by tracing a beam ray. The intensity of the laser absorbed on the keyhole wall due to the inverse Bremsstrahlung absorption of the plasma was calculated. The effects of such factors as the multiple reflections, the vertex angles and the diameters of the keyhole on the intensity distribution of the laser absorbed on the keyhole wall were studied. After comparing the laser intensity absorbed due to the inverse Bremsstrahlung absorption of the plasma with that absorbed due to the Fresnel absorption on the keyhole wall, the different effects of the two energy absorption mechanisms on forming and keeping the keyhole were analyzed.