TEMPERATURE-DEPENDENCE AND SCATTERING OF TOUGHNESS OF A533-B STEELS IN DUCTILE-BRITTLE TRANSITION REGION

Temperature dependence and scattering of the critical COD, delta-c, and J-integral values in the ductile-brittle transition region were investigated with A533 B steels the microstructures of which were widely varied. delta-c's at the maximum loads were in a linear relation with J/sigma-Y with a proportional constant of 0.49 irrespective to microstructures and test temperatures. It suggests that the stress.strain field at the crack front area could be described with the Hutchinson, Rice-Rosengren solutions even at the D-B transition region. Linear relations also existed between delta-c as well as J and the stretch zone width, szw, but the data were grouped according to the relative locations of the test temperatures in the transition region. Analysis in terms of tearing modulus was also examined, suggesting that the resistance to the crack extension is temperature and microstructure dependent. It was discussed that the temperature dependence of the toughness and its scattering at a given test temperature could be discriminated in a sense that the former is related to the resistance of the crack extension while the latter is to the transition to the stable crack or brittle crack initiation.