Analysis of 316H creep crack initiation data at 550 degrees C using a crack tip constraint parameter

Abstract

In this paper, 316H creep crack growth data at 550 degrees C are analysed to investigate the effect of inplane 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.