多轴疲劳模型对比研究及其在核电结构热疲劳寿命预测中的应用

压水堆核电站余热排出系统冷热水混合区管道发现的热疲劳问题影响核反应堆的安全。本文通过一种采用单轴疲劳试验数据拟合疲劳寿命曲线，进而用于预测多轴疲劳寿命的分析方法，基于文献中的疲劳试验数据，对Dang Van模型、Matake模型和Fatemi-Socie模型进行了余热排出系统冷热水混合区管道材料304L不锈钢疲劳寿命预测结果的对比研究。基于余热排出系统冷热水混合区管道的三维简化有限元模型，分别应用Dang Van模型、Matake模型和Fatemi-Socie模型对管道热疲劳寿命进行了预测，并与试验结果进行了对比验证。研究结果表明，基于应变（含平均应力修正）的Fatemi-Socie模型比较适用于304L不锈钢的疲劳分析，其热疲劳寿命预测结果相对Dang Van模型、Matake模型较合理。

Comparative Investigation of Multiaxial Fatigue Model and Application in Thermal Fatigue Life Prediction of Structure in Nuclear Power Plant

The problem of thermal fatigue cracks discovered in the pipes of mixing zones of cold and hot water in residual heat removal systems of pressurized water reactors is related to the safety of nuclear reactors. In this paper, a methodology for predicting the multiaxial fatigue life by using a reference curve fitted by uniaxial fatigue experimental data was adopted. For 304L stainless steel, which was the material of the pipes of mixing zones of cold and hot water in residual heat removal systems, the fatigue lives were predicted by using Dang Van, Matake and Fatemi-Socie criteria based on the fatigue experimental data collected from literature and the results of prediction were compared. The thermal fatigue lives of the pipe were computed by using Dang Van, Matake and Fatemi-Socie criteria based on a simplified 3-dimensional finite element model of the pipes of mixing zones of cold and hot water in residual heat removal systems, and the numerical results were compared with the experimental results. The results show that Fatemi-Socie criterion, which is based on strain (correlated by mean stress), is more suitable for the 304L stainless steel. Moreover, the predicted thermal fatigue life using Fatemi-Socie criterion is more reasonable than those using Dang Van and Matake criteria.