中文摘要：

为了准确的模拟出激光深熔焊接中小孔的动态变化过程,根据小孔内激光的能量吸收机制,采用光线追踪法来描述小孔对激光能量的多重反射吸收作用,建立了描述激光深熔焊接过程中瞬态小孔和运动熔池耦合行为的三维数值模型.通过对30CrMnSiA 钢激光焊接过程的数值模拟,得到焊接熔池-小孔的动态演变过程与相应的温度场和流场分布.结果表明,激光深熔焊接过程中小孔深度呈周期性变化并伴有高频振荡特征,而小孔的振荡是焊接不稳定性和缺陷形成的重要原因.通过对激光焊接过程动态监测系统获得的熔池-小孔图像和焊缝宏观形貌的分析,进一步验证了模拟的现象和规律,表明本文建立的数值模型和方法能够比较准确地模拟激光深熔焊接中小孔的动态行为.

英文摘要：

In order to accurately simulate the dynamic process of keyhole formation during laser deep penetration welding, a ray tracingmethod based on Particle level set method is proposed to describe the multiple reflections Fresnel absorption effect of keyhole wallon laser energy, and a three-phase unification mathematical model of laser keyhole welding is established to combine the effects ofthree dimensional transient keyhole and transient weld pool. Dynamic process of keyhole formation and its correspondingtemperature and flow field distributions are obtained by numerical modeling of laser deep penetration welding process of30CrMnSiA steel. The results shows that the depth and shape of keyhole have an obvious characteristic of periodic changes and aphenomenon of high frequency oscillations in process of laser deep penetration welding, and the high frequency oscillations ofkeyhole is the main factors of laser welding instability and defects forming. Through comparative analysis of the images of weldpool and keyhole obtained by the dynamic monitoring system and the macrograph of welding seam, the results show that theexperiment result is in accordance with the simulation one approximately and the simulation method and the mathematical modelcan accurately simulate the dynamic process of keyhole formation during laser deep penetration welding.