Model for grain boundary sliding and its relevance to optimal structural superplasticity - Part 5 - A unique numerical solution and its reliability

A few of the constitutive equations used to describe the mechanical response of superplastics are examined. The problems associated with the estimation of the values of the model constants are discussed. Attention is focused on the model for grain boundary sliding controlled optimal structural superplasticity recently proposed. A numerical procedure that allows the unambiguous determination of the material constants of this model is presented and validated by analysing the experimental data pertaining to a few systems. It is shown that this method allows the determination of the material constants with a limited number of experimental points. A comparison of the predictions with the experimental results show's that this model accurately describes optimal superplastic flow, for Regions I and II up to the point of inflection in the sigmoidal In(stress)-ln(strain rate) curve. The advantages of the present method over others available in the literature ale noted.