Influence of Specimen Type, Crack Length and Evaluation Method on Quasi-Static and Dynamic Fracture Toughness Properties

This paper provides a comparison of the influence of specimen type (single edge bend (SE(B)) specimen vs. compact tension C(T) specimen), specimen dimensions (crack length ratio a/W, thickness B) and the effect of the loading rate on fracture toughness properties. In the lower ductile-brittle transition region the quasi-static Master Curve (MC) reference temperature T₀ is evaluated according to ASTM E 1921-08ae1 and the dynamic MC T₀ according to the Swiss guideline HSK-AN-425, which is compared with a modified ASTM E 1921-08ae1 approach. The ductile behaviour was evaluated by quasi-static JR curve testing in which the applicability of several evaluation standards are compared (ASTM E 1820-08, ISO 12135, ESIS-P2). Quasi-static and dynamic MC temperatures T₀ deviate by up to 68 K. SE(B) specimens with shorter crack lengths (a/W = 0.3) than prescribed by ASTM E 1921 yield the same T₀ as specimens with a/W = 0.5. Thus, such short crack surveillance specimens are also suitable for fracture mechanical assessments. SE(B) specimens of B = 0.4T (1T = 1 inch) up to 3.2T show comparable T₀, proving the transferability of fracture mechanical test results of small surveillance specimens to heavy-walled RPV structures.