In this paper, 316H creep crack growth data at 550 °C are analysed to investigate the effect of in-plane constraint on creep crack initiation times. A constraint parameter is proposed to quantify the difference between an actual opening stress and the Riedel-Rice opening stress field in plane strain, using experimentally measured C*. Test data analysis shows that creep crack initiation times can be well characterized by the C* integral with the proposed parameter. A modified form of a model due to Nikbin, Smith and Webster is suggested, and scatter in predictions is shown to be reduced from ~40 to ~5.

中文翻译：

---

使用裂纹尖端约束参数分析550°C下316H蠕变裂纹的起始数据

本文分析了550°C下316H蠕变裂纹扩展数据，以研究面内约束对蠕变裂纹萌生时间的影响。提出了一个约束参数，使用实验测量的C *来量化平面应变中实际打开应力和Riedel-Rice打开应力场之间的差异。测试数据分析表明，蠕变裂纹的起始时间可以通过所建议参数的C *积分很好地表征。建议采用Nikbin，Smith和Webster提出的模型修改形式，预测中的散布值从40降低到5。