The role of inhomogeneous deformation in high-temperature ring compression testing

Elastic-viscoplastic constitutive equations that enable the modelling of rate effects, temperature effects and dynamic recrystallization are employed to model the ring compression test at high temperatures. The effects of strain rate and temperature on the calibration curves, used widely to characterize frictional behaviour in forging, are investigated. Both strain rate and temperature are found to influence the calibration curves obtained, and it is found that the influence derives from the dependency of dynamic recrystallization processes on strain rate and temperature. The coupling between the deformation and the recrystallization process is found to lead to the establishment of significantly different strain fields with different strain rates, and it is this that leads to the dependency of the calibration curves on strain rate and temperature. A methodology has been presented for the determination of friction calibration curves for hot forging of high-performance materials, which accounts for strain rate effects, temperature effects and recrystallization processes. The method is likely to be useful to industries involved in the high-temperature processing of high-performance components.