Work Hardening at Large Strains, Theory and Experiment

This paper is offered as an essential description of constitutive behavior at large plastic strains, as observed in cubic metals at low temperatures. The fact that Stage IV occurs in all f.c.c. metals tested to date is emphasized and also a model for Stage IV is presented that is based on the accumulation of dislocation debris. The stages of deformation were defined by Diehl1 for stress-strain curves of f.c.c. single crystals, tested in tension. Stage I corresponds to Easy Glide, Stage II to Athermal Hardening and Stage III to Dynamic Recovery. For the study reported here, short tube torsion (“Lindholm”2 design) tests were used in order to attain plastic strains of as much as 600%. In many cases, a further stage, Stage IV, is observed that is a linear stress-strain curve extending to very large strains.