Effect of Gradient Plasticity on Crack Initiation and Propagation in the Ductile-Brittle Transition Region of Ferritic Steel

Abstract

Micro-crack initiation in ductile-brittle transition region of ferritic steel is often observed through cracking of carbides near or at ferritic grain boundary. The main reason is that the dislocation pile-up at a grain boundary induces high stresses in the carbide. This mechanism cannot be modelled by classical plasticity. In the present study, the effective gradient plasticity (scalar gradient plasticity) together with cohesive zone models is employed in a unit cell model to adress this mechanism at the microscale.