预热对激光束钎熔焊温度场和应力场的影响

研究预热对铍环激光束钎熔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有限元方法，假定沉积到钎缝表面的激光束能量为Gauss分布，通过在焊接前添加一个能量密度低，但有效加热半径大的工况分析预热温度。研究表明，预热使铍环钎缝外表面的焊接最高温度增加，温度梯度减小，熔深增加；采用预热工况焊接后，钎缝附近塑性变形区残余应力明显减小，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，表明二者应力变化趋势基本一致。

Effect of preheat on temperature and stress fields of laser brazingfusion welding

The effects of preheat on the temperature and stress fieldsof beryllium ring during laser brazing fusion welding are studied. A axialsymmetry model and a thermal-mechanical decoupled finite elecmentmethod (FEM) are adopted, and assuming that the energy distribution oflaser beam is Gauss distribution on the brazing seem surface. Preheat isrealized by a special heat method. The rcsuhs show that the temperatureat outer surface rises, the temperature gradient decreases, the brazingseam depth increases. The residual stress near the brazing seem withplastic deformation decreases obviously and increases at the heat aff~tedzone. As a whole, preheat makes the distribution of brazing seem residualstress more homogenize. Comparing the residual stresses at outer surfaceof beryllium ring by FEM to that from x-ray stress measurement, the trendis identical.