基于直流电压降法的传热管疲劳裂纹扩展速率测量

介绍了基于直流电压降法测量蒸汽发生器传热管690合金轴向疲劳裂纹扩展速率的销加载拉伸方法。该方法与其他方法相比较，可以直接采用原始管状材料，在线连续测量管状试样在不同应力强度因子下的疲劳裂纹扩展。通过对标准紧凑拉伸试样的类比分析，建立传热管试样的销加载拉伸模型，并对该模型进行电学和力学有限元模拟分析，确定直流电压降数据采集方法。验证试验采用核电蒸汽发生器用690合金传热管，分别研究了室温和高温325℃空气中载荷和温度对材料疲劳裂纹扩展速率的影响，试验结果采用Paris-Erdogan公式进行拟合，吻合度较好。扫描电镜下观察端口形貌，疲劳裂纹的扩展为穿晶形式，在穿晶断口上观察到明显的疲劳辉纹和微塑性区。

Fatigue crack growth rate measurement of steam generator tubes based on DCPD method

A new testing method based on direct current potential drop ( DCPD ) and pin loading tension ( PLT ) method was introduced for evaluating the fatigue crack growth rate of steam generator tubes. In analogy to compact tension ( CT) specimens, a testing model was established by using thin-walled tube specimens, and the corresponding mechanical and electrical finite element analyses were made respectively, which determined the data acquisition plan based on DCPD method. Fatigue test was taken on nick-el-based alloy 690 used for nuclear power steam generators, and the effects of applied load and temperature were discussed. The result was modeled with the Paris-Erdogan equation and accorded well with this model. Scanning electron microscopy ( SEM) examination of the fatigue fracture surfaces revealed transgranular attack, and the transgranular regions of the fatigue fracture surfaces were covered with striation-like features.