ELASTOPLASTIC 3-DIMENSIONAL CRACK BORDER FIELD .3. FRACTURE PARAMETERS

The variations of the amplitude of the stress field, the triaxiality of stress and the crack tip opening displacement against the triaxial stress constraint T are analysed in detail based on the work of Part I and Part II of this study. The concrete form of T in front of a through-thickness crack in contained yielding is proposed and the actual distribution of stresses in the front of elastic-plastic through-thickness cracks is predicted. Good agreement with finite element results confirms the analytical findings. Furthermore, an elastic-plastic fracture criterion, including the effect of crack tip blunting on the parameter characterizing fracture, has been developed and proven to be a material constant independent of plate thickness for a given material state. Both ductile and mixed ductile-brittle fracture have been discussed.