Abstract
It is well known that various arm displacements, associated with different initial stress intensity factor KIAPPLIED, in DCB test in accordance with NACE TM0177 can result in different measured critical stress intensity factor for sulfide stress cracking (KISSC) values in corrosive environments. However, other factors, such as initial notch tip locations, i.e. initial notch length, can also affect the KIAPPLIED and that can ultimately affect the KISSC and KLIMIT measurement. This study shows that the effects of initial notch locations, with ai varying from standard 1.125 (chevron tip), 1.250 (lined up EDM tip) and 1.375 (current standard EDM tip) to non standard and extended 1.500 and 1.625 in DCB specimens, on the KIAPPLIED, KISSC and KLIMIT through experimental testing using C110 and T95 materials. Three-dimensional finite element analysis (FEA) was conducted for the compliance and KIAPPLIED was analyzed for various specimen configurations. It was found that varying notch locations leads to a linear dependence of KISSC on KLIMIT that is similar to that of wedge induced arm displacement method. The KLIMIT measured by varying initial notch locations shows almost identical relation to the one measured by traditional arm displacement variation. The corresponding sulfide stress cracking mechanism in DCB testing is also discussed. This study suggests a possible new approach to obtain KLIMIT by varying notch locations instead of wedge induced arm displacements for better accuracy and more constant measurements of KISSC. Additional work in this area is recommended.
