Kinematic element modelling of horizontal two-roll piercing

Abstract A reliable mechanical model is developed in the two-dimensional kinematic element frame-work to analyse the influence of setting-mill conditions on the stress, strain rate, strain and final seamless-tube outer diameter. The billet velocity is split into a rotational rigid part and a translational viscoplastic part. The stationary flow region is discretized into five kinematic elements for the viscoplastic velocity field part, the boundary of elements being dependent on the roll-setting conditions, plug geometry and incipent central cavity dimensions. Viscoplastic materials behaviour is introduced in the constitutive equations of the viscoplastic flow. The contact and friction conditions are described by a sub-layer friction model which depends on the bulk material flow stress and on the sliding interface velocity. The related computation routines are able to run on any personal computer working in the DOS environment and most results are obtained in quasi real-time with the usual hardware configurations. Predictions of final outer diameter are found to be well related to industrial results for a horizontal two-roll piercing mill.