Double cantilever beam (DCB) testing is one of the NACE SSC tests, with the advantage that it provides a quantitative value and not just a “pass or fail” statement. OCAS implemented a specialized DCB equipment allowing the continuous recording of the drop in load and crack length during the test.
The well-known method D is frequently used for the quality control of OCTG grades. It is a dedicated test which delivers relevant and quantitative (K1SCC) information but only in the crack arrest condition. However, from experience we know that the dynamics of crack propagation are important to understand the phenomena responsible for cracking.
OCAS designed and implemented an instrumented DCB equipment to study more in-depth the crack evolution during method D testing. The set-up allows the continuous recording of the load drop and crack length during the experiment. The methodology immediately visualises e.g. the effect of sample size on the crack evolution during the test. Multiple materials are currently being tested to study the link with the materials’ microstructure. In a next phase, the diffusion parameters derived from permeation testing will be incorporated in a combined mechanics-diffusion model to obtain a better insight in the interaction between H pick-up and crack propagation.
“By combining the results of the permeation measurements with the capabilities of our new instrumented DCB tester, OCAS is able to better understand and address the sour corrosion resistance of different materials.”