Analysis of 316H Creep Crack Initiation Data at 550℃ using A Crack Tip Constraint Parameter

Abstract In this paper, 316H creep crack growth data at 550℃ 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.