NACE TM0177 Method a Uniaxial Tensile Testing: Learnings from Investigations on Test Procedure

The NACE TM0177 Method A Uniaxial Tensile test using a proof-ring device is extensively used in order to assess the Sulfide Stress Cracking (SSC) susceptibility which can occur on Oil Country Tubular Goods (OCTGs) and Line Pipe (LP). It is also well admitted that different test methods may not necessarily provide the same ranking. This is the reason why replicate testing is advisable to tighten as much as possible the scattering of the SSC threshold. Nevertheless, SSC test results can show statistical variability for the same material. The aim of this paper is to check whether the applied stresses are uniformly distributed within the tensile specimen. Shared data with regard to the presence of bending and torsion phenomena are compared when stressing the test specimen thanks to the use of PZ strain gauges. Order of magnitude is also quantified on different specimen geometry and or equipment. Moreover, discussion on the influence of other parameters such as machining, polishing, storage of the specimens and test procedure is presented as well to share the experience on the Uniaxial Tensile test.