脉冲激光焊接的数学模型

基于金属材料熔化、汽化界面二维扩展机制建立了脉冲激光的焊接模型。该模型是将激光作用区和脉冲作用时间分离为离散单元后计算焊缝断面形状的，提出以深熔小孔中的腔内光强动态再分布机理更精确地描述焊缝断面形状。腔内光强再分布机制主要考虑腔壁菲涅耳反射。光强叠加是基于与入射角无关的相干强度叠加。每次反射后的位置单元的确定采用光线追迹法。数值模型分别算出功率P、光斑尺寸α、吸收率α（材料一定，波长变化，吸收率亦改变）等参数变化所导致的液相线断面曲线的变化，并给出作用时间变化时，断面曲线的变化规律。计算结果表明，焊缝断面形状受脉冲功率、光斑直径、脉冲作用时间影响较大，这和实际的焊接情况吻合，同时，理论结果也可解释焊缝断面曲线走向突变现象。

Mathmatical Model of Pulsed Laser Welding

Based on the metal melt and vaporized interface 2D propagation mechanism,this paper founds the pulsed laser welding model.This model divides the interactive zone and pulse duration into many units,which is used for weld profile calculation.We put forward the intensity redistribution mechanism in keyhole cavity to exposit the weld seam cross section profile preciously.This intensity redistribution mechanism in keyhole cavity mainly take up the Frenel preciously at cavity wall,and the intensity superimposition is attributed to noncoherent superimposition,which is independent on the incident angle.The local unit after every reflection is decided by ray trace method.This model gives out the weld profile along with the laser pulse power P,focus diameter a,absorptance α,and the profile curve variation vs the interactive time t.The theory results show that the weld seam cross section profile is influenced significantly by laser pulse power,focus diameter and pulse duration.This is correspondent to actual weld situations.Meanwhile,the theory results can explain the weld cross section curve zigzagged characteristics.