Experimental and numerical investigations on ductile-to-brittle transition in a carbon steel

Using finite element analysis and metallographic observations, the stress field ahead of stationary and growing cracks and the ductile-to-brittle transition mechanism in a carbon steel have been evaluated. Compared to a stationary crack, a growing crack elevates both the stress triaxiality and the opening stress on the remaining ligament. The micro-criterion for cleavage fracture for both stationary and growing cracks is postulated to be identical. Ductile-to-brittle transition may occur as a result of increasing constraint for different specimen geometries. Based on the stress fields ahead of the stationary and growing cracks and the measured value of local cleavage stress, the ductile-to-brittle transition temperature has been successfully predicted in the compact tension (CT) specimen geometry.