Absrract
The NACE TM0177 Standard Method D (Double Cantilever Beam-DCB) test provides a measure of resistance to crack propagation in sour environment; expressed in terms of a critical intensity factor, KISSC for Sulfide Stress Cracking. Testing conditions must be such to ensure crack initiation since DCB is a crack-arrest-type of fracture mechanics test. To ensure crack initiation, the formation of a sharp crack tip by fatigue pre-cracking is permitted by the mentioned standard; however the conditions under which pre-cracking procedure must be performed are not so well established and have been modified over the years. Definition of pre-cracking load is crucial for obtaining the true value of KISSC since an excessive load is known to produce an increment of the plastic zone at the crack tip that could delay crack initiation, generating an overestimation of KISSC that could not be otherwise noticeable. The main objective of this work is to quantify the effect of pre-cracking load on sour resistance for the High Strength Steel grades tested with different arm displacement. Tests were performed at 24°C in NACE solution A and API 5CT SR39.3 solution for C110 and in NACE solution A for the 125 sour service grade.
