Analysis of the Effect of Pre-Crack Curvature in Mini-C(T) Specimen on Fracture Toughness Evaluation

Abstract

Abstract The appropriate test method for determination of reference temperature (To) using the Master Curve is necessary for the structural integrity assessment of the reactor pressure vessel, prescribed in ASME CC N-830-1 and JEAC4206-2016. To can be determined using the fracture toughness test specimen, such as miniature C(T) (Mini-C(T)), following ASTM E1921 or JEAC4216, which prescribe the test method including pre-crack straightness criteria. Part of the requirements in the ASTM E1921 were revised after a decade. Additionally, the ASTM’s allowable crack front curvature of the specimen has become different from that of the JEAC. Given that the pre-crack curvature of the Mini-C(T) specimen might affect the To determination because of the variation of the plastic constraint. Herein, we evaluated the effect of the crack curvature on the fracture toughness (KJc) evaluation or To determination using the Mini-C(T). The finite element analyses (FEAs), including the Weibull stress analysis, were employed to provide quantitative information on the requirement of the pre-crack curvature in ASTM E1921 and JEAC4216. FEAs revealed that the specimen with an upper limit on the curvature decreased the plastic constraint, indicating a higher KJc value. The Weibull stress analysis showed that the straightness requirement according to JEAC4216-2015 was reasonable for the To determination. However, when the specimens with upper limit crack curvature per ASTM E1921-21 were used for To determination, the To was lowered significantly.