安全端焊接残余应力对裂纹尖端力学参量的影响

1.西安科技大学 机械工程学院,陕西 西安 710054; 2.布鲁内尔大学 工程设计与自然科学学院,英国 伦敦 UB8 3PH

机械工程; 结构完整性; 数值模拟试验; 应力腐蚀开裂; 焊接残余应力

Influence of residual stress in safety end on mechanical parameters at crack tip
GUO Rui1,2,XUE He1,CUI Ying-hao1

(1.College of Mechanical and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China; 2.College of Engineering,Design and Physical Sciences,Brunel University,London,UB8 3PH,United Kingdom)

mechanical engineering; structural integrity analysis; welding residual stress; material heterogeneity; stress and strain

DOI: 10.13800/j.cnki.xakjdxxb.2018.0319文章编号: 1672-9315(2018)03-0479-05

备注

焊接残余应力是导致核电一回路安全端异种金属焊接接头引导力腐蚀开裂(SCC)的主要因素之一,同时焊接接头区域材料力学性能不均匀性使得SCC裂纹尖端力学场分析变得更为复杂。为了了解核电一回路压力容器安全端异种焊接结构中残余应力对裂纹尖端力学参量的影响,本文通过有限元手段分别利用预定义温度场法和导入预应力法对核电一回路安全端焊接接头中的残余应力分布进行模拟,并计算分析了焊接残余应力作用对安全端焊接接头中SCC裂纹尖端主要力学参量的影响。研究表明,导入预应力法是较理想的焊接接头残余应力场模拟方法; 裂尖应力、应变以及J积分均与残余应力的分布规律有很大的关联性; 当裂纹长度小于管壁厚度的三分之一时,裂尖应力应变和断裂参量随裂纹长度增加而增大,之后趋于平稳; 当裂纹长度接近30 mm时裂尖法向应力由正变负,裂尖应力应变随裂纹长度的增大而减小,有可能造成SCC裂纹扩展停滞。研究结果为日后定量预测安全端SCC裂纹扩展历程奠定了一定的理论基础。

The welding residual stress is one of the main factors that lead to the Stress Corrosion Cracking(SCC)in dissimilar metal welded joints in the safety end of nuclear power plants.Additionally,the mechanical properties of the SCC crack tip become more complicated due to the heterogeneity of the mechanical properties of the welded joint.To understand the influence of residual stress on the crack tip mechanical parameters in the dissimilar welded structure of the safety end of a nuclear power circuit pressure vessel,the predefined temperature field method and the stress field introduction method were respectively used in Finite Element software.The residual stress distribution was simulated,and the effects of welding residual stress on the key mechanical parameters of the SCC crack tip in the welded joint were calculated and analyzed.The results show that the stress field introduction method is relatively an ideal method for the simulation of the residual stress field in welded joints.The stress,strain and J-integral around crack tips all have a significant correlation with the distribution of residual stress.When the crack length is less than one-third of the thickness of the pipe wall,the stress,strain and fracture parameters around crack tips increased while the crack length grew,but tend to be stable at the end.When the crack length is close to 30mm,the normal stress of the crack tip changes from positive to negative,and the crack tip stress and strain decreased then the crack length increased,which may cause SCC crack propagation stagnated.Our research provides a theoretical basis for the quantitative prediction of the SCC crack propagation history of the safety end in the future.