INFLUENCE OF DYNAMIC STRAIN AGEING ON DUCTILE FRACTURE OF A C-MN STEEL

摘要

Ductile fracture of a C-Mn steel was characterised by tensile tests performed in a large temperature range (from 20 to 350°C) on round notched specimens. The experimental results revealed a sharp drop of fracture strain around 250°C. This corresponds to the domain of dynamic strain ageing (DSA) occurrence. The Portevin-Le Chatelier (PLC) effect, which is the most classical effect of DSA, was modelled on round notched specimens with a mechanical behaviour model including the strain ageing effect. Local approach to fracture was applied to predict the ductile fracture using the Rice and Tracey criterion. The predictions are rather close to the experimental results for the low and high temperatures. In the DSA domain, the approach predicts a decrease of the fracture strain but with a lower magnitude than the experimental one. Therefore, DSA has an effect on mechanical behaviour but also on fracture mechanisms. Consequently, the fracture criterion has to be modified in the presence of DSA.