Low Constraint Toughness Testing of Two Single Edge Notched Tension Methods in a Single Specimen

Abstract

Singleedge notched tension (SE(T) or SENT) specimens have been increasingly proposed as a lowconstraint toughness test to measure toughness of line pipe materials, as the crack tip constraint approximates a circumferential surface flaw in a pipe under loading. The clamped SE(T) singlespecimen procedures recently developed by Shen and Tyson (2008, “Fracture Toughness Evaluation of High Strength Steel Pipe,â€‌ ASME Paper No. PVP200861100; 2008, “Development of Procedure for LowConstraint Toughness Testing Using a SingleSpecimen Technique,â€‌ CANMET Materials Technology Laboratory, Technical Report No. 200818 (TR)) and Tang et al. (2010, “Development of the SENT Test of StrainBased Design of Welded Pipelines,â€‌ 8th International Pipeline Conference, IPC 2010, Calgary, AB, Canada) have both used in common the use of a clamped singlespecimen of similar geometry and relied on the unloading compliance technique for crack size estimation. In the former case, a single clip gauge is attached to the integral knife edge and the cracktip opening displacement (CTOD) is estimated by means of a JintegraltoCTOD conversion, similar to the procedure of ASTM E182011. The latter uses a pair of clip gauges mounted on an attachable raised set of knife edges to estimate CTOD at the original crack tip position by a triangulation rule. Consolidating these two sets of clip gauges in a specimen makes direct comparisons of two SE(T) methods under identical test conditions: material, specimen geometry, equipment, test temperature, and operator (Weeks et al., 2013, “Fracture Toughness Instrumentation Techniques for SingleSpecimen Clamped SE(T) Tests on X100 Linepipe Steel: Experimental Setup,â€‌ 6th Pipeline Technology Conference, Ostend, Belgium). In this study, SE(T) testing employing these two SE(T) methods on a single specimen was conducted on B أ— B shallowcracked (a/W ∼ 0.35) specimens of two X70 pipeline girth welds. This paper discusses details of the two SE(T) methods and techniques on the same specimen.