A comparative study on Johnson Cook, modified Zerilli-Armstrong and Arrhenius-type constitutive models to predict elevated temperature flow behaviour in modified 9Cr-1Mo steel

In this paper, a comparative study has been made on the capability of Johnson Cook (JC), modified Zerilli-Armstrong (ZA), and strain-compensated Arrhenius-type constitutive models for representing the elevated temperature flow behaviour of modified 9Cr-1Mo steel. The experimental stress-strain data from isothermal hot compression tests over a wide range of temperatures (1123-1373 K), strains (0.1-0.5) and strain rates (0.001-1 s(-1)) were employed to evaluate the material constants of these constitutive models. Suitability of these models were evaluated by comparing the correlation coefficient and absolute average error of prediction, ability to describe the deformation behaviour, number of material constants involved, and the computational time required to evaluate these constants. It is observed that the JC model is inadequate to provide good description of flow behaviour of modified 9Cr-1Mo steel in the above hot working domain. Predictions of the other two models are in good agreement with the experimental data. However, strain-compensated Arrhenius-type equation could track the deformation behaviour more accurately though it requires more number of material constants and more computational time to evaluate these constants than the modified-ZA model. (C) 2009 Elsevier B.V. All rights reserved.