A Modified Recovery-Creep Model and Its Evaluation

Abstract

Based upon previous treatments of the recovery-creep theory a model. has been formulated that takes into account the separation of the applied stress into an effective stress and an internal stress and the experimentally determined stress-dependence of the activation area. The model describes the time- and stress-dependence of the creep rate in the primary and the secondary stages. It is shown that the theory adequately simulates the experimental creep curves. The attainment of constant true and apparent activation energies, and of a constant exponent in the creep rate/stress power law, are interpreted as different consequences of the internal stress being approximately equal to the applied stress at low stresses and high temperatures. The physical significance of the apparent activation energy is discussed in terms of the model.