NACE TM0177-2016 Method D testing is a common methodology to evaluate sulfide stress cracking performance in a sour environment. In this methodology, fracture surfaces are evaluated and some invalid cases are documented in accordance to TM0177 Method D 11.6.1. Specifically, edge cracks which occur from the bottom of side groove and prevents crack propagation is a key issue for this methodology and the optimization of side-groove configuration from V shaped side groove to U shaped side groove has been studied to prevent the occurrence.

It was revealed that U shaped side groove can reduce the occurrence of edge cracks by former FEA analysis and Method D test using test specimens in a certain machine shop. On the other hand, there would be some effect of machining of side groove in terms of crack propagation. In this study, we prepared Method D test specimens from API 5CT C110 with V and U shaped side-groove machined by machining company A and B. Afterwards, corrosion tests in 1 bar H2S, pH 2.7 (standard condition for API 5CT C110) were performed. As a result, edge crack was reduced by applying U shaped side groove prepared by both machining shops. It can be concluded that U shaped side groove is generally effective to prevent the occurrence of edge crack.

Subject
Test methods, Materials, Grooves, Materials performance, Optimization, Compliance, Machinery, Fracture surfaces, Machining, Steel, Cracks, Stress corrosion cracking, Test specimen
Keywords:
DCB, NACE TM0177 Method D, edge crack, side-groove
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2023
Association for Materials Protection and Performance (AMPP)
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