预热对铍环激光束钎焊过程的影响研究

研究预热对铍环激光束钎焊过程温度场和应力场分布的影响。采用轴对称模型和热力解耦的有限元方法，并假定沉积到钎缝表面的激光束能量为Gauss分布，预热通过在焊接加热前添加一个能量密度低、有效加热半径大的单独工况实现。结果表明，预热使镀环钎缝外表面焊接最高温度增加，温度梯度减小，但焊深明显增加；采用预热工况焊接后，钎缝附近塑性变形区焊接残余应力明显减小，而热影响区残余应力增大。从整体分布来看，预热使铍环外表面焊接残余应力分布均匀化。对铍环外表面钎缝附近焊接残余应力进行X射线应力测试，并与有限元分析结果对比，二者应力变化趋势基本一致。

Effect of Preheating on Laser Brazing Process of Beryllium Ring

The effects of preheating on temperature and stress fields of beryllium ring during laser brazing process were studied. An axial symmetry model and a thermal mechanical decoupled FEM were adopted, and it is assumed that the energy distribution of laser beam is Gauss distribution on the weld pool surface. Preheat was realized by a special heat method. The results show that the temperature at outer surface rises and the temperature gradient decreases, but the weld depth increases. The welding residual stress near the weld line with plastic deformation decreases obviously and increases at the heat affected zone (HAZ). As a whole, preheating makes the distribution of weld residual stress more homogeneous. Comparing the results of the welding residual stresses at outer surface of beryllium ring by FEM to that from X ray stress measurement, the stress trend is identical.