A COMPUTATIONAL-PROCEDURE FOR THE SIMULATION OF DUCTILE FRACTURE WITHLARGE PLASTIC-DEFORMATION

It is now well-known that the applicability of the single-parameter J- approach is restricted only to high constraint crack geometries and ma terials of low ductility. Consequently, there is a need to develop a d uctile fracture criterion that does not suffer from the geometry depen dence exhibited by the J-integral. However, the ability of any analyti cal model to provide accurate description of fracture initiation and p ropagation in a ductile material is contingent upon its capability to model the large deformations that occur in the fracture process zone. The purpose of this paper is to describe the formulation and implement ation of an efficient finite deformation algorithm that can be used fo r the prediction of elasto-plastic fracture in ductile materials where J-dominance is violated. An incrementally objective mid-interval inte gration algorithm is used in conjunction with an efficient polar decom position scheme for the accurate integration of the plasticity equatio ns in the presence of large deformations. Both rate-dependent and rate -independent plasticity models are included. A sophisticated node rele ase algorithm for the simulation of crack propagation is also implemen ted. The application of continuum damage models as potential ductile f racture criteria is discussed. The overall efficiency of the code is e nhanced by means of the BFGS (Broyden, Fletcher, Goldfarb and Shanno) solution algorithm. Three elasto-plasticity problems that involve fini te deformation are analyzed in order to assess the accuracy of the sol ution procedure. The effectiveness of including material damage in the constitutive behavior to predict ductile failure in a notched tensile specimen is addressed.