State variable approach to deformation phenomena in FCC metals: Dissertation

The phenomenological deformation theories for plastic deformation are surveyed, with emphasis placed on the state variable model proposed by Hart. The work hardening behavior of some FCC (face centered cubic) metals is explained in terms of Hart's model and a new work hardening correlation is proposed, based on the separation of athermal and thermal contributions to the work hardening coefficient.The effects of strain aging on the state variable treatment of plastic deformation in stainless steel (SS) are determined and a new treatment based on the evolution of drag stress is suggested.Furthermore, the analysis of strain aging experiments performed on a variety of materials shows that in addition to the hardness parameter, another state variable, i.e. the rate parameter, is generally needed if strain aging is to be accounted for.In addition, it is shown that an indentation load relaxation experiment may potentially be used to obtain pertinent material information for deformation models.