Fracture toughness of high strength seamless pipe steel from SE(T) and SE(B) specimens evaluated by different standards

Abstract

Recently released, BS 8571:2014 standard offers an alternative for the experimental determination of fracture toughness and resistance curves of metallic materials from SE(T) specimens. Similar in stress conditions and constraint to cracked tubes, specimens in SE(T) geometry should yield less conservative toughness values than conventional high‐constraint specimens, such as SE(B) geometry. However, the convention to determine the J‐integral fracture toughness proposed in the new BS standard is different from ASTM standards. In this work, SE(T) and SE(B) specimens of similar dimensions of a tough high‐strength seamless pipe steel were tested following the BS 8571:2014 and ASTM E1820‐16 standards, respectively. Because of the different standardized definitions, SE(T) specimens yield lower fracture toughness than SE(B) specimens, which could lead to more conservative results in structural integrity analysis. This investigation also suggests the introduction of the blunting line concept in the BS 8571:2014 standard in order to minimize this problem.

A node release approach to estimate J‐R curve for single‐edge‐notched tension specimen under reversed loading

“…Hammond and Fawaz derive the linear‐elastic K I solution for plain‐side SE(T) specimens without side grooves, while Liu et al suggest a function of stress intensity factor for side‐grooved SE(T) specimens. Filgueiras et al compare the J‐R curves and toughness values determined for SE(T) specimens through different standards. Ruggieri proposes a η function for the SE(T) specimen made of a homogeneous material, and Parades and Ruggieri evaluate the η factor for the SE(T) with a weld centreline crack.…”