汽轮机焊接转子残余应力模拟及其对疲劳寿命的影响

Simulation of Residual Stress in Welded Steam Turbine Rotor and Its Effects on Fatigue Life

焊接转子是核电汽轮机低压转子的必然选择,而焊接导致的残余应力可能影响转子的疲劳寿命。文中考虑焊接过程的马氏体相变,采用有限元方法,分析了汽轮机焊接转子窄间隙埋弧焊接头的残余应力分布及其对局部疲劳寿命的影响,得到了与实测残余应力相吻合的结果。研究发现:焊缝部位内、外表面的轴向残余应力均为压应力,且环向残余应力高于轴向应力。与无残余应力情况相比,焊接接头热影响区内外表面的高周、低周疲劳寿命都有不同程度的降低。且在此区域内,焊接残余应力增大疲劳裂纹扩展驱动力。

Welded rotors are used for steam turbine widely. However, residual stress induced by welding may have a great influence on fatigue life. Considering the martensite phase transformation during the welding process, the finite element method was employed to simulate the welding residual stress. The effect of residual stress on local fatigue life distribution was investigated in a turbine low-pressure rotor welded by narrow gap submerged arc welding. A good agreement between the simulated residual stress and those of experiment was achieved. It reveals that the axial residual stresses are compressive on both inner and outer surface in weldment zone. In addition, the magnitude of axial residual stress is less than that of the hoop residual stress. Due to the welding residual stress, both high and low cycle fatigue life decrease on the inner or outer surface of heat affected zone. Nevertheless, fatigue crack propagation is promoted by the welding residual stresses in this area.