ON THE PERFORMANCE OF KINEMATIC HARDENING RULES IN PREDICTING A CLASSOF BIAXIAL RATCHETING HISTORIES

It is well known that strain-symmetric axial cycling of thin-walled me tal tubes in the presence of pressure results in a progressive accumul ation (ratcheting) of circumferential strain. It was previously demons trated that the prediction of the rate of ratcheting under constant in ternal pressure, by nonlinear kinematic hardening models, is very sens itive to the hardening rule adopted. It was shown that the Armstrong-F rederick hardening suitably calibrated and used in a class of models c an yield reasonably good predictions of the rate of ratcheting for a r ange of cycle parameters. In this paper, the subject is revisited in t he light of further experimental results involving simultaneous cyclin g of the internal pressure and the axial strain. Experiments and analy ses were performed for a family of five such biaxial loading histories . A similar sensitivity to the kinematic hardening rule used in the mo dels was observed in all the new loading histories. Furthermore the ha rdening rule calibrated in the constant pressure experiments was found to yield accurate predictions for three of the loading histories cons idered and poor predictions for the other two. The reasons for this va ried performance are analyzed and some recommendations for implementat ion of such models in structural applications are made.