Current Knowledge Concerning the Influence of Specimen Geometry on the Measured Fracture Toughness in the Transition Regime

The main issues that affect fracture toughness of carbon steel materials and welds are well understood. However, staff responsible for qualifying the material or weld procedures does not fully understand the more subtle factors. Materials and weld procedures were once qualified in a thinner material thickness are failing to pass qualification testing using the material thickness increases. Specimen parameters such as size, a/W ratio, and specimen aspect ratio can increase or reduce the measured fracture toughness of the material in the transition regime. This paper is an overview of the how these factors influence the measured fracture toughness.