A thermodynamic model of ideal cyclic viscoplasticity

In order to formulate a rational theory of viscoplasticity it is indispensable to apply a correct geometric interpretation of the deformation process and to use the second law of thermodynamics as the master law for all irreversible processes. In this paper an effort is made towards involving cyclic effects into the theory. Ideal viscoplasticity means that stress rate is not included in yield function. Formulation of such a theory is the subject of the next section. For the sake of applicability it is essential to consider isotropic materials in the important case of small thermoelastic but finite plastic deformations and this is given in the third section. An elementary example dealing with uniaxial stress state is the subject of the subsequent section. Summary and conclusions are aimed to show shortcomings and advantages of the theory compared with some other important scientific results and theories. (orig./GL)