A MICRO-MODEL OF DUCTILE FRACTUKE AND IT’S APPLICAION TO CONSTRAINED FRACTURE

The damage evaluation near a crack tip in different fracture specimens andsmall scale yielding model are analyzed in detail.It is proposed that the initiation of ductilefracture is equivalent to saying that the damage at a characteristic position ahead of thecrack reaches a critical value. Using this model the macroscopic fracture toughness, inagreement with experimental data and with theoretical fracture toughness independent ofconstraint are obtained.