Predictions of roll force under heavy-reduction hot rolling using a large-deformation Tconstitutive model

A large-deformation constitutive model applicable to the calculation of roll force and torque in heavy-reduction rolling has been presented. The concept of the volume fraction of dynamically recrystallized grains, which depicts the flow stress softening correctly with the level of strain, strain rate and temperature has been newly introduced in the proposed model. The material constants required in the proposed model have been obtained by a series of hot-torsion tests. A laboratory-scale hot-plate rolling experiment, together with three-dimensional finite element analysis coupled with the proposed model, has been performed to investigate the accuracy of the proposed constitutive model. The soundness of the proposed model has been demonstrated through a series of finite element simulations with temperature and reduction changed. The finite element predictions of roll force based on the proposed model and the experimental results was shown to be in fair agreement whereas those based on the Misaka– Yoshimoto model, in which dynamic recrystallization was not considered, failed to predict the roll force precisely at heavy reduction. The results also revealed that, for a typical reduction, the flow stress softening effect was not observed during deformation, whereas the effect was considerable when the material underwent heavy reduction.