ABSTRACT
The plastic yield zones around the end of a crack have been the subject of intense investigation, particularly since the definition of the HRR stress and strain fields some 20 years ago [1,2]. The whole treatment of the fracture process really depends on the extent of these zones, in relation to the crack length, and the size of the uncracked ligament but the detailed description of the zones has received only passing discussion, largely as a result of the experimental problems involved in obtaining data which will allow an accurate evaluation, particularly in view of the three-dimensional nature of the problem. In some test situations this need give little cause for anxiety, since experimental conditions may be controlled to give a defined yield zone. In general, however, such control cannot be exercised and knowledge of details of the yield locus may well become important.
