铍材激光钎焊过程中熔池流场和热场的动态模拟技术

Numerical simulation for transient behavior of fluid flow and heat transfer in laser-brazing pool of beryllium plate

根据YAG激光钎焊的物理特征,建立了基于旋转高斯体热源与高斯面热源相结合的混合热源模型。通过对铍材钎焊温度场、钎缝断面形状模拟结果与实际热循环曲线以及钎焊接头形状的对比,验证了模型建立的准确性。为了能够反映固液相变过程中潜热等对熔池动态行为的影响,建立了激光钎接熔池流场与热场动态变化过程三维数学模型和适合非稳态、非线性、多相区和强耦合特性的数值求解方法。进一步研究了熔化潜热、预热温度和保护气体剪切力对熔池内流场分布的影响。

A hybrid heat source model that based upon rotary-Gauss body heat source model and Gauss area heat source was established in the paper,the numerical simulation of hybrid welding temperature field and welding seam sectional form was performed and the advice of parameters modification was brought forward. Compared with the experimentally measured value,the results showed that the calculated weld size was in good agreement with the experiment result,the simulation model established could simulate the fluid flow field of the laser weld pool accurately. In order to reflect the effect of latent heat on the dynamic behavior of weld pool in process of solid-liquid phase,three-dimensional mathematical model on transient behavior of fluid flow and heat transfer in laser brazing weld pool was established. According to the characteristics of transient,nonlinear,multi-phase and strong coupling feature between the governing equations,a numerical simulation algorithm method was developed,which could evidently speed up the iterative convergence rate. Further,the effects of latent heat of fusion,the preheating temperature and shearing force of shield gas on the distribution of flow field were studied in the paper.