Low constraint fracture toughness testing for master curve reference temperature determination using 10 mm-thick SE(B) and SE(T) specimens

The constraint correction methodology for defect assessment is not widely applied in fitness-for-service codes in the nuclear industry and there are a limited number of testing standards to account for low-constraint testing. In this work, fracture toughness testing was performed with two different types of alloy steels. SE(B), C(T), and SE(T) specimen configurations were used, along with varying a/W ratios and specimen sizes, allowing for varying levels of constraint. New quality assurance measures related to selection of testing temperature, crack front straightness, and compliance for low constraint specimens are suggested. The results show that the SE(B) specimens are sensitive to CMOD measurement point location. Future work should be focused on improving and validating the instrumentation and analysis practices for low constraint specimens. Yet, the obtained SE(T) T₀ values follow models predicting the effect of constraint loss developed using larger specimens. The work impacts the development of quality criteria for future low constraint testing standards.