Comparison of J-integral from single specimen SE(T) tests on API-5L X100 line pipe steel Available to Purchase

The clamped single-edge notched tension (SE(T)) specimen has seen increased use as a single-specimen testing scheme to determine tearing resistance curves in high strength steel pipe. The SE(T) specimen with appropriate notch geometry is a low-constraint specimen designed to reduce conservatism in the toughness measurement when compared to other toughness testing methods. The J-integral is robust and simple to calculate from data obtained by the use of several direct experimental measurements. This study employed a wide variety of instrumentation on API 5L X100 SE(T) specimens with fixed test parameters for direct comparison. This paper presents the details of the instrumentation and determination of the J-integral used in developing resistance curves. The results of this study show that directly measuring strain gradients can yield commensurate results to other non-codified methods currently under development for evaluating J-resistance curves in pipeline steels. Such experimental comparisons are needed to assure that the analysis methods used in both test-method development and in structural analysis accurately simulate the actual material behavior. Because the high fracture toughness of modern pipeline steels allows the development of extensive strain fields before significant tearing, practical strain gradient measurement techniques with local strain capacity up to 20 % will be needed to more accurately quantify the comparison between calculations and experiment. To the authors' knowledge this direct comparison has never been conducted and published by use of independent instrumentation on the same specimens.