A COMPUTATIONAL APPROACH TO DUCTILE CRACK-GROWTH UNDER LARGE-SCALE YIELDING CONDITIONS

Mode I crack initiation and growth under plane strain conditions in to ugh metals is computed using an elastic-plastic continuum model which accounts for void growth and coalescence ahead of the crack tip. The m aterial parameters are the Young's modulus, yield stress and strain ha rdening exponent of the metal, along with the parameters characterizin g the spacing and volume fraction of Voids in material elements lying in the plane of the crack. For a given set of these parameters and a s pecific specimen, or component, subject to a specific loading, relatio nships among load, load-line displacement and crack advance can be com puted with no restrictions on the extent of plastic deformation. Simil arly, there is no limit on crack advance, except that it must take pla ce on the symmetry plane ahead of the initial crack. Suitably defined measures of crack tip loading intensity, such as those based an the J- integral, can also be computed, thereby directly generating crack grow th resistance curves. In this paper, the model is applied to five spec imen geometries which are known to give rise to significantly differen t crack tip constraints and crack growth resistance behaviors. Compute d results are compared with sets of experimental data for two tough st eels for four of the specimen types. Details of the load, displacement and crack growth histories are accurately reproduced, even when exten sive crack growth takes place under conditions of fully plastic yieldi ng.