The effect of testing environment on DCB (Double Cantilever Beam according to NACE
TM0177-2005 method D) performance of C110 material was evaluated, following the introduction in
ballots on a mild sour environment in the frame of C110 grade standardization into API spec 5CT / ISO
11960.
Various products of C110 material were tested. The DCB tests were performed on the same
materials in NACE TM0177 test solution A saturated by 100% H2S gas (standard environment) with an
arm displacement of 0.51 mm as well as in a buffered test solution saturated by 7% H2S in a carrier of
nitrogen gas (mild environment). The arm displacement aimed for was 0.89 mm.
In both environments, the resulting KIssc values were in the expected range. However, the range
between low and high KIssc values obtained in the mild environment was much higher than for the tests
performed in TM0177 test solution A. Increase in the test duration for mild sour environment resulted in
decreasing KIssc, which indicates that a test duration of two weeks might not be sufficient to reach the
equilibrium of load and crack length.
These results, as well as compliance analyses of the various DCB tests, are discussed in detail.
Additional influencing factors such as effects of arm displacement and fatigue pre-cracking are also
addressed.
Keywords: SSC, NACE TM0177 method D, Double Cantilever Beam, test condition, API,
compliance analysis, fatigue pre-cracking, test duration