Fracture toughness characterisation in the ductile-to-brittle transion and upper shelf regimes using pre-cracked Charpy single-edge bend specimens

Abstract

Toughness data of pre-cracked Charpy SE(B) specimens are compared with those of standard C(T) specimens in the upper shelf and ductile-to-brittle transition regimes. Charpy sized SE(B) specimens provide ductile fracture toughness data which are compatible with those of standard C(T)-specimens. Statistical methods such as the Exponential Curve Fitting Method, the Engineering Lower Bound Toughness Method and the Master Curve Method are used to provide meaningful lower bound cleavage fracture toughness estimates from the toughness scatter of the Charpy sized SE(B) specimens in the ductile-to-brittle-transition regime. In this regime SE(B) specimens provide cleavage toughness data which tend to be non-conservative compared to those of standard C(T)-specimens. At the lower bound toughness level (5% cleavage failure probability) –corresponding to 100 N/mm- the ductile-to-brittle transition curves of SE(B) specimens are reduced by 5-8 °C compared to those of standard C(T) specimens. A constraint correction function for SE(B) specimens is presented that can be used to make cleavage toughness data of SE(B)-specimens compatible with those of standard C(T) specimens.