激光焊接瞬态小孔内部金属蒸汽动力学数值模拟研究.docVIP

  激光焊接瞬态小孔内部金属蒸汽动力学数 值模拟研究# 陈鑫，庞盛永，陈伟东，周建新* 5 10 15 20 25 30 35 40 （华中科技大学材料成形及模具技术国家重点实验室, 武汉 430074） 摘要：基于激光焊瞬态小孔和动态熔池间断耦合模型，考虑反冲压力、环境压力以及蒸汽的 可压缩性等因素，耦合无粘性 Euler 方程建立了光纤激光焊接瞬态小孔内部可压缩金属蒸汽 流动行为三维数学模型，模拟了瞬态小孔内部金属蒸汽的流动行为，获得了金属蒸汽密度、 压力、速度、马赫数等物理量在瞬态小孔内部的三维分布。结果表明：在所研究的工艺条件 下，瞬态小孔内部的金属蒸汽状态非常不稳定，其密度、压力、速度和马赫数分布很不均匀， 且随时间变化十分剧烈。金属蒸汽在小孔中下部能够形成一个高压区，使蒸汽有向下运动的 趋势。小孔开口处的金属蒸汽的喷出速度随时间呈显出先快速增加至一峰值，然后逐渐减小 的趋势。小孔内部金属蒸汽的最大速度可以达到数百米每秒，其最大速度以 3kHz~6kHz 的 频率作高频振荡。模拟得到的金属蒸汽动力学特征与金属蒸汽的高速摄影实验结果、光信号 分析实验结果以及文献结果良好吻合。 关键词：激光深熔焊接； 瞬态小孔； 可压缩蒸汽 A study on the dynamics of compressible vapor plume in a transient keyhole during deep penetration laser welding CHEN Xin, PANG Shengyong , CHEN Weidong, ZHOU Jianxin (State Key Laboratory of Materials Processing and Die Mould Technology, HuaZhong University of Science and Technolody, WuHan 430074) Abstract: The dynamics of compressible vapor plume in a transient keyhole during laser welding of 304 stainless steel is studied by direct numerical simulation. The transient evolutions of keyhole and weld pool dynamics are solved by our recently developed keyhole welding model. The model rigorously considers the coupling effect of most important factors of laser welding, such as recoil pressure, surface tension, Marangoni effect, and multiple reflections Fresnel absorptions etc. A recently developed ambient pressure dependent recoil pressure model is also incorporated to include the effect of ambient pressure. The vapor plume dynamics inside the keyhole is assumed to be mainly driven by the recoil pressure and modelled by compressible Euler equations. The time dependent three-dimensional density, pressure, velocity and Mach number distributions of the plume inside a transient keyhole are solved. The results show that under the investigated welding conditions the vapor plume inside the keyhole is usually very unstable, and the distributions of density, pressure, velocity and Mach number are far from uniform and vary greatly with time. The vapor plume i