局部加热冷却法对水轮机转轮焊接残余应力场的影响

针对焊缝成形的特点,提出了改善叶片焊接残余应力分布状态的局部加热冷却法,并利用数值模拟技术研究了局部加热冷却法对转轮残余应力场的影响,得到了叶片危险区域的残余应力在局部加热过程中的变化情况以及转轮局部加热的优化方案.结果表明,采用局部加热冷却的方法可以有效地减小叶片危险区域的残余拉应力峰值.残余应力的降低效果与加热时间、加热温度以及加热面积成正比,并且焊接残余应力随加热距离的增加呈先降低后增大的趋势.

Influence of local heating-cooling on welding residual stress of francis turbine runner

On basis of local heating-cooling method which is brought out to improve the distribution of welding residual stress in blade according to the property of weld formation,influence of local heating-cooling method on runner's residual stress field is studied by numerical simulation technology.Moreover,the change process of welding stress in the blade dangerous area and the optimizing scheme of local heating are attained.The result shows that the method of local heating-cooling can decrease the residual tensile stress peak in dangerous area of the blade.The effect on decreasing residual stress is directly proportional to heating time,heating temperature and heating area.Moreover,with the augmentation of heating distance,the residual stress in dangerous area can decrease and with further the augmontation the residual stress will increase.