Dislocation Dynamics Modelling of the Ductile-Brittle Transition

Many materials like silicon, tungsten or ferritic steels show a transition between high temperature ductile fracture with stable crack grow and high deformation energy absorption and low temperature brittle fracture in an unstable and low deformation mode, the ductilebrittle- transition. Especially in steels, the temperature transition is accompanied by a strong increase of the measured fracture toughness over a certain temperature range and strong scatter in the toughness data in this transition regime. The change in fracture modes is affected by dynamic interactions between dislocations and the inhomogeneous stress fields of notches and small cracks. In the present work a dislocation dynamics model for the ductile-brittle-transition is proposed, which takes those interactions into account. The model can explain an increase with temperature of apparent toughness in the quasi-brittle regime and different levels of scatter in the different temperature regimes. Furthermore it can predict changing failure sites in materials with heterogeneous microstructure. Based on the model, the effects of crack tip blunting, stress state, external strain rate and irradiation-induced changes in the plastic flow properties can be discussed.

HENNECKE Thomas;  HAEHNER Peter; 

2009-12-17

IOP PUBLISHING LTD

JRC56049

0965-0393,   

http://iopscience.iop.org/1757-899X/3/1/012005/pdf?ejredirect=.iopscience,    https://publications.jrc.ec.europa.eu/repository/handle/JRC56049,   

10.1088/1757-899X/3/1/012005,