Roller Extrusion of a Ceramic Paste

The roller extrusion of a stiff model ceramic paste has been studied experimentally using a fully instrumented roller apparatus that allows simultaneous measurement of roller separation, separating force, torque, and roll surface pressure. The paste exhibited no noticeable wall slip and little expansion, detaching from the rollers shortly downstream of the nip. Data collected over reduction ratios of 0.92-0.15 and speeds of 1.5-30 rpm (7.9-160 mm s^-1) showed consistent trends when plotted against reduction ratio. A small strain rate dependence was observed, which was consistent with the rheological parameters obtained from the Benbow-Bridgwater characterization approach that models the material as a yield strength material. The data were also compared with the results from three models for rolling based on the plasticity approach: an upper bound model, a lower bound model, and a hot metal rolling model originally presented by Orowan. The experimental and predicted results showed good agreement for the latter model, and it was then extended to incorporate a simple strain rate dependency based on the Benbow-Bridgwater characterization approach. These results indicate that this characterization approach can be used to predict or gauge the rolling performance of such soft-solid materials.