A computational procedure for the simulation of ductile fracture with large plastic deformation

Abstract

It is now well-known that the applicability of the single-parameter J-approach is restricted only to high constraint crack geometries and materials of low ductility. Consequently, there is a need to develop a ductile fracture criterion that does not suffer from the geometry dependence exhibited by the J-integral. However, the ability of any analytical model to provide accurate description of fracture initiation and propagation 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 implementation of an efficient finite deformation algorithm that can be used for the prediction of elasto-plastic fracture in ductile materials where J-dominance is violated. An incrementally objective mid-interval integration algorithm is used in conjunction with an efficient polar decomposition scheme for the accurate integration of the plasticity equations in the presence of large deformations. Both rate-dependent and rate-independent plasticity models are included. A sophisticated node release algorithm for the simulation of crack propagation is also implemented. The application of continuum damage models as potential ductile fracture criteria is discussed. The overall efficiency of the code is enhanced by means of the BFGS (Broyden, Fletcher, Goldfarb and Shanno) solution algorithm. Three elasto-plasticity problems that involve finite deformation are analyzed in order to assess the accuracy of the solution procedure. The effectiveness of including material damage in the constitutive behavior to predict ductile failure in a notched tensile specimen is addressed