10321 Simplified Transient Approach for Modeling Crack Growth in DCB Specimen Testing

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Product Number: 51300-10321-SG

ISBN: 10321 2010 CP

Author: Sebastian Cravero, Richard Bravo, Hugo Ernst

Publication Date: 2010

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The presence of hydrogen sulfide in oil and gas production is continuously increasing and the dangerous consequences for materials through hydrogen embrittlement mechanisms are of special concern to oil companies and pipe manufacturers. Furthermore, more severe working conditions in terms of mechanical loads in H₂S reservoirs require high grade steels. The high grade of these steels make difficult to attain sulfide stress cracking resistance (K_ISSC) values as high as conventional low steels grades. Therefore, it is of fundamental importance to evaluate the methods used to determine the fracture resistance in sour environment.

In this work, a simplified transient approach was developed to estimate the crack growth rate in double cantilever beam samples used in the NACE TM0177 standard method D. The evolution of the electrochemical solution-surface system was taken into account through a variation law with the time adjusted based on experimental results and a finite element analysis.

As a result, the instantaneously K_applied, and consequently the K_ISCC, was estimated. The predictions were compared with experimental testing results in terms of K_applied vs. K_ISSC. Additionally, the effect of testing conditions, i.e. variation of H concentration with time, was assessed with the transient model.

Keywords: Sour environment, sulfide stress cracking, double cantilever beam, hydrogen diffusion